Seasonal Abundance of Waterbirds at Point Reyes: a Coastal California Perspective

Home , Bodega Bay, Bolinas Bay, Bolinas Lagoon, Lake Earl, Marbled godwit, Olema Valley

WESTERN BIRDS

Volume 20, Number 4, 1989

SEASONAL ABUNDANCE OF WATERBIRDS AT POINT REYES: A COASTAL CALIFORNIA PERSPECTIVE

W. DAVID SHUFORD, GARY W. PAGE, JULES G. EVENS, and LYNNE E. ß STENZEL, Point Reyes Bird Observatory, 4990 Shoreline Highway, Stinson Beach, California 94970

Numerous studies undertaken since 1940 document seasonal abundance patternsof aquaticbirds in Californiawetlands. Many of these studiesfocus only on shorebirdsat a singlesite (e.g., R. W. Storer 1951, Recher 1966, Jehl and Craig 1970, and Gerstenberg1972) but together they span the length of the state from San Diego Bay (Jehl and Craig 1970) to HumboldtBay (Gerstenberg1972). The mostambitious shorebird censusstudy is that of Jurek (1972, 1973, 1974), who usedvolun- teer observersto count shorebirdsin wetlandsthroughout the state. State and federal agencies have also conducted waterfowl censuses throughoutCalifornia. Some researchershave attempted to quantifythe seasonal abundance patterns of all aquatic birds in wetland habitat: Gerdes (1970) at Morro Bay, Winkler et al. (1977) at Mono Lake, Bollmanet al. (1970) and Gill (1972a) in San FranciscoBay, Swarthet al. (1982) in salt pondsin southSan FranciscoBay, King et al. (1987) at San Elijo Lagoon, and Funderburkand Springer(1989) at lakesEarl and Talawa. Collectively,these studiesand the more general accountsof Grinnelland Miller (1944), Cogswell(1977), McCaskieet al. (1979), and Garrettand Dunn (1981) providea very usefuldescription of the seasonal usepatterns of aquaticbirds in California. Since 1965 volunteersand the staff of Point ReyesBird Observatory (PRBO) have conductedcensuses of birds in the wetlands of the Point Reyes Peninsula,Marin Co., California. These censuses,which extend up to 10 consecutiveyears at a singlesite, providemore detailedinfor- mation on variationin bird numbersthan has been reportedpreviously for Californiawaterbirds. In this paper we describethe seasonaluse patterns of aquaticbirds of two estuaries,one lagoon,and the inshorezone Western Birds 20: 137-265, 1989 137 WATERBIRDS AT POINT REYES of the oceanoff southernPoint Reyes,and, when appropriate,compare these'patterns to those found elsewherein coastalCalifornia. We also examine the influence that variations in rainfall have on variations in bird abundance,on the timingof species'arrival and departure,and on inter- site variationin occurrencepatterns on Point Reyes. Beyonddescribing the dynamicsof this localsystem, the data provide a baselineon the populationsizes and seasonalabundance patterns of birds in most wetlandsof the Point Reyes Peninsula. In contrastwith many of California'swetlands, the Point Reyeswetlands remain relatively pristine. Much of the studyarea is currenfiyprotected wildlife habitat and shouldremain so into the future, thereby permitting continuedmoni- toringof changesin bird abundancein a naturalsystem.

STUDY AREA AND METHODS

The studyarea includedwetlands of the PointReyes Peninsula (bounded on the east by BolinasLagoon, the Olema Valley, and TomalesBay), Marin Co., and BodegaHarbor, SonomaCo. (Fig. 1). Seasonalabundance patterns were derived from countsof aquaticbirds on Bolinas Lagoon, Limantour Estero, Abbott's Lagoon, and the nearshorecoastal waters between Stinson Beach and the Point ReyesLighthouse. Supplemental information was also obtained from censusesat Drake's Esteroand BodegaHarbor and incidentalsightings as describedbelow. We calledBolinas Lagoon, Limantour Estero, Bodega Harbor, Drake's Estero, and Tomales Bay seasonalestuaries (see Pritchard 1967) becausethey are semi- enclosedbodies of watersubject to dailytidal action, and their saltwater is measur- ablydiluted by freshwater only from Octoberthrough April. In contrast,Abbott's Lagoon'slower basinis separatedfrom the oceanby a barrierbar that is only occasionallybreached during storms, extremely high tides, or periodsof heavy runoff. Breachingcauses a rapid drop in water leveland subjectsthe lagoonto tidalaction for a few days. Abbott'sLagoon is essentiallybrackish, minimally influ- encedby tidal action,and bestfits the definitionof a true lagoon(Caspers 1967). For simplicity,we refer to the estuariesand Abbott'sLagoon as wetlands,even thoughthey alsocontain deepwater habitat. Rain is highlyseasonal with about95% of the yearlytotal falling from October throughApril (Fig. 2). From 1967 to 1982, June throughMay rainfallon the coast6 krn northwestof BolinasLagoon averaged 88.3 cm (SE = 8.1); extremes were 44.9 and 40.7 cm in the droughtyears of 1975-76 and 1976-77, respectively, and 147.0 and 132.6 cm in the wettestyears, 1972-73 and 1981-82, respectively.

Census Locations

Bolinas Lagoon. BolinasLagoon, 24 km northwestof San Francisco,is a Marin Co. Nature Preserve. At mean low tide 26.0% of the 587-ha estuaryis open water, 57.2% unvegetatedtidal fiat, and 16.8% salt marshor upland. More informationon the area is availablein Ritter (1969), Ritter and Brown (1973), Bergquist(1978), and Page et al. (1979). We conducted247 censusesat BolinasLagoon (hereafterBolinas) between June 1971 and May 1982 at a frequencydeclining from one every 10 daysin 1971 and 1972 to one per monthfor only part of the year in 1981 and 1982. Censuseswere duringspecific 5-day periodsif tideswere suitable(Fig. 3) or the nearestappropriate period if they were not suitable(see Page et al. I979 for further detailsof censusmethods).

138 WATERBIRDS AT POINT REYES

Lirnantour Estero. Limantour Estero, a Point Reyes National Seashore (PRNS)natural area 20 km northwestof Bolinas,is borderedby hills,freshwater impoundments,a spit with scatteredhigh dunes, and a channel to the ocean shared with Drake's Estero. Several intermittent streams run into the estero. At the time of our study,at mean low tide 47.6% of the 331-ha estuarywas open water,41.2% non-vegetatedtidal fiat, and 11.2% saltmarsh or upland. Six freshwater impoundmentsabutting the esteroadded an additional63.9 ha of aquatic bird habitat. Since 1982 breaksin dikeshave drained28.1 ha of pond habitat, part of which was restoredto tidal action.

Bodega Harbor SONOMA

COUNTY

,, Antonio"

Bay

Abbott'sLagoon - MARIN

COUNTY

ß PointReyes Station San Cordell i Banks PointReyes ,C• Pablo Ughthous•• ' • • Drake'sBay • Bay

Double o .,.•, BolinasLagoon

Duxbu•fReef Rocky Point

GULF

OF THE

FARALLONES

Fa•'allan islands

Figure 1. Point Reyes study area. a, Bird Rock; b, Kehoe Marsh; c, Chimney Rock; d, Drake's Beach Pond; e, Horseshoe Pond; f, Schooner Bay; g, Glenbrook and Muddy Hollow ponds; h, Inverness;i, Olema Marsh; j, Point Resistance;k, Five Brooks Pond; 1, Abalone Flat; m, Bolinasand Bolinassewer ponds;n, Palomarin;o, AudubonCanyon Ranch;p, BolinasBay. The 10 numberedsub-areas denote sections of the inshorezone censusedbetween September 1980 and September1981.

139 WATERBIRDS AT POINT REYES

The 146-ha northernextension of the estuary(upper Limantour) was not cen- susedinitially (see below) because of its distancefrom the censusroute along the spit. One hundredsixty-six counts, encompassing the southern169 ha of the esteroand 16.4 ha of impoundments(Muddy Hollow Pondand a smallnearby pond), betweenJune 1967 and June 1981 contributedto the data base for all species. An additional63 countsof pondsfrom July 1965 to May 1967 aug- mentedthe data for the CinnamonTeal, Redhead,and Ring-neckedDuck, which were restrictedprimarily to the impoundments. Although censuseswere dis- tributedfairly evenly throughout the year(Fig. 3), theywere not takenin specified 5-day periodsor with respectto tidesuntil 1973-74. Abbott'sLagoon. This undevelopedarea lies2 km northwestof the northern end of Drake'sEstero in PRNS. Two interconnectedfreshwater ponds, derived mainlyfrom winter runoff,total 32 ha and are linkedto the northeastshore of the lower,brackish 83-ha lagoon,which temporarily becomes tidal on rare occasions t1971(57.6 - cm)197•

1975-1976 • (121. (92.0 cm) (44.9 :m) • 3o t 974-1975 0 20 v lO 5o 1977-1978 1978-1979 (40.7 ½m) (97.4 cm) (67.1 cm)

20 'so10 t1976-1977 I 5O 401979-1980(98.5 cm) 1980.-1981

o ...... J J A S 0 N 0 J F M Aid J. (65J A8 cm•S 0 N D J F M A M JJASONDJFMAM MONTHS

Figure2. Rainfallpatterns at Palomarin,6 km northwestof Bolinas.Upper left, monthlyrainfall for theperiod 1967-1982. Solidcircles, mean; vertical bars, one standarddeviation; open circles, minimum and maximum values. Other graphs, rainfallby month for individualyears; yearly totals in parentheses. WATERBIRDS AT POINT REYES when the barrier bar is breached. Even when the bar is intact the surface area of the lagoon variesby a factor of about 2, dependingon rain and evaporation. Dunesand an extensivesand flat borderthe Iagooffssouthwest margin. We conducted135 censusesof the 11,5 ha of combinedlagoon and pond habitatbetween •July 1973 and •June1982. The censusesdid not correspondwith specified5-clay time periodsor tidesuntil •June 1980. Supplementalcensus areas: Drake's Estero, upper Limantour Estero, and BodegaHarbor. At monthlyintervals from October1979 to May 1980 and from

IO- BOLINAS LAGOON -

c• O • I i I I I I I o

• •0 LIMANTOUR ESTERO ' I I --

z 0-1 I I I I I I I I I I I

I0- ABBOT• LAGOON

-- 5- I • it:'::; : : :: ' : ' o_,.i,,I i i, i , , I I :I I :I I I iI I I J J A S 0 N D J F M A M

Figure3. Numbersof censusesof aquaticbirds taken at threeweftands during 10- dayperiods (alternate 5-clay periods) from 5-9 Junethrough 21-25 Maybetween 1967 and 1982. Censusestaken outside these 5-clay periods are talliedin the closest5-clay period. Dottedlines for Bolinasindicate censuses on whichonly shorebirdswere counted. Dotted lines for Limantour indicate censusesvalid for only the CinnamonTeal, Ring-neckedDuck, and Redhead(see Methods). Solid linesfor Abbott'sindicate censuses used for graphsof the Black-belliedPlover, SemipalmatedPlover, Marbled Godwit, Western Sandpiper, Least Sandpiper, and Dunlin;all censusesused for otherspecies (see Methods).

141 WATERBIRDS AT POINT REYES

September 1980 to June 1981 we conducted18 censusesof the 964-ha Drake's Esteroand 39.1 ha of adjacentponds. From October1979 to May 1980 we con- ducted8 monthlycensuses of the 146-ha north-southarm of LimantourEstero and 37.7 ha of adjacentponds. From November1978 to February1979 and from November 1979 to May 1980 we conducted 11 monthly censusesof BodegaHarbor, a 368-ha estuary55 km northwestof Bolinas. Outer coast. We made 12 countsof aquaticbirds inshore in the oceanfrom RockyPoint, justsouth of StinsonBeach, to the Point ReyesLighthouse within 4 days of monthly censusesin adjacentestuaries between September 1980 and September1981. One to three peoplecounted non-flying birds as far from shore as they couldsee with binocularsand 20x spottingscopes in eachof 10 sub-areas (Fig. 1). We refer to sub-areas6-10 as Drake'sBay. Flyingbirds were not tallied to ensure that counts represented birds definitely using study area waters. Assumingan effectivecensus distance of 1500 m from shore,we estimatedthe area covered as 9400 ha of coastal water.

Unidentified Birds

Those taxa regularlyposing identification problems in wetlandswere Western and Clark's grebes, scaups,dowitchers, small sandpipers(Least Sandpipers, Western Sandpipers,and Dunlins), and gulls. Both speciesof large grebes, scaups,and dowitcherswere pooledfor all analyses.Unidentified small sandpipers were apportionedamong those identified as describedby Pageet al. (1979). The seasonalabundance patterns of gullsare basedon identifiedbirds only, underesti- mating the abundanceof most speciesexcept for Bonaparte'sand Heermann's gulls. Despitethis limitation the graphsof gullsare usefulfor definingpatterns of seasonal occurrence. On censusesof nearshorewaters identification of the speciesof smallgrebes (Hornedand Eared),scoters, and particularlyloons often proveddifficult because of the longdistances between birds and observers.We allocatedunidentified birds to speciesby usingproportions of thoseidentified from the samesub-area of the coast unlessnumbers of those identifiedin a sub-areawere very small. In such casesthe proportionsof identifiedbirds in eitherthe easternor westernfive sub- areas were used to apportion the unidentifiedbirds by speciesand sub-area. Unidentifiedloons constituted9-86% (median 20%) of the ones identifiedon the 10 coastalcensuses, unidentified scoters 6-60% (median26%), and unidentified smallgrebes 0-24% (median 10%), except on the September 1980 census,when only 3 of 25 smallgrebes were identified.

Other Data Sources

We usedsightings from publishedand unpublishedsources to supplementour censusdata, especiallyfor rare to very rare species. Foremost among these sourceswere the quarterlyseasonal reports of the MiddlePacific Coast Region of American Birds, formerlyAudubon Field Notes (citedas AB or AFN), and the compilationof recordsfrom which the publishedaccounts were derived, the "American Birds Notebooks"(cited as ABN: observer'sinitials) on file with the regionaleditors. UnpublishedPRBO records,the authors'field notes, and per- sonal communicationsfrom other observers(cited as PRBO or the observer'sinitials) were an additional source of data. Observerswhose initials are cited are David G. Ainley (DGA), Peter Allen (PA), StephenF. Bailey(SFB), LaurenceC. Binford (LCB), Bob Boekelheide(BB), Gerald Brady (GB), Courtney Buechert (COB), Scott Carey (ScC), Ted (TAC) and Zoe Chandik (ZCh), Bill Clow (BC), Howard L. Cogswell(HLC), ChrisCutler (CC), Dave DeSante(DDeS), Richard Ditch (RD), RichardA. Erickson(RAE), JulesG. Evens(JGE), Marc Fenner (MFe),

142 WATERBIRDS AT POINT REYES

Rudi Ferris (RF), William B. Gladfelter (WBG), Philip E. Gordon (PEG), Keith Hansen (KH), Rob Hayden (RHa), R. Phil Henderson (RPH), Burr Heneman (BHe), David A. Holway (DAH), Alan S. Hopkins (ASH), Steve N. G. Howell (SNGH), StuartJohnston (SJ), DurrellD. Kapan (DDK), John Kelly (JPK), Susan Kelly (SK), Joe Kennedy(JKe), Bill Lenarz (BiL), Phil Lenna (PL), Gary S. Lester (GSL), Baron McClean (BMc), Peter J. Metropulos (PJM), Grace Miller (GM), JosephMorlan (JM), Dan P. Murphy (DPM), Gary W. Page (GWP), BenjaminD. Parmeter (BDP), Steve Perry (SP), Ed Piccolo (EP), Lina Jane Prairie (LJP), William M. Pursell(WMP), Peter Pyle (PP), C. J. Ralph (CJR), J. Van Remsen (JVR),Barry Sauppe(BSa), Kenneth Schulz (KSc), David Shuford (DS), John Small (JS), Bruce Sorrie (BSo), Rich Stallcup(RS), Lynne E. Stenzel(LES), Robert M. Stewart(RMS), Nick Stow (NS), Chris Swarth (CSw), Ted Van Velzen(TVV), Nils Warnock (NW), Alice Williams (AW), David Wimpfheimer (DWm), Jon Winter (JW), and Keiko Yamane (KY). We also used information from the Point Reyes PeninsulaChristmas Bird Count (CBC) and, secondarily,the Marin Co. (southern), Tomales Bay, and Drake's Bay CBCs, publishedin American Birds. Unlessotherwise noted, the only recordsof extremerarities that we report have been reviewedand accepted by the CaliforniaBird RecordsCommittee (CBRC). These recordsare cited as CBRC and either have been publishedin CBRC reports(Winter 1973, Winter and McCaskie 1975, Luther et al. 1979, Luther 1980, Luther et al. 1983, Binford 1983, Binford 1985, Morlan 1985, Roberson1986, Dunn 1988) or have been acceptedby that committeeand will be publishedin the near future(D. Roberson, CBRC Secretary,in litt.). We followedAinley and Sanger's(1979) definitionsfor the zonesin the ocean usedto describethe distributionof sea-goingbirds. "Oceanic"describes waters of the deep ocean from the continentalslopes beyond the continentalor insular shelves. "Neritic" describes waters over the continental shelf. The neritic zone can be subdivided into inshore and offshore zones. The demarcation between the inshoreand offshorezones is the line beyondwhich the bottomis too deep for a diving seabirdto reach--a depth of approximately70 m (Ainley and Sanger 1979). We placequotes around "offshore" and "inshore"when we refer to literature that definesthese terms differenfiy or not at all.

Data Analysis We determinedseasonal abundance patterns for all but very rare speciesfrom the censusesof Bolinas Lagoon, Limantour Estero, and Abbott's Lagoon. Becausemost speciesare scarceto absentin the wetlandsin summer,we defined a year as extendingfrom I Juneto 31 May. For all butvery rare species,the minimum,mean, and maximumnumber of birdsin alternate5-day periods (Fig. 3) are graphedby wetlandand species.Bolinas shorebird graphs derived from censuses fromJune 1971 to May 1976 (e.g.,Fig. 25) werepublished by Page et al. (1979). Bolinasgraphs for non-shorebirds(e.g., Fig. 4) are basedon 176 censusesfrom AugustI972 to May I980, exceptfor that for the AmericanCoot, whichis based on only 125 censusesfrom August 1972 to May 1976 becauseof the sharpdrop in numbersafter that period. Mostgraphs for Abbott'sLagoon are basedon all 135 censusesfrom July 1973 to June1982. We usedonly the 75 censusestaken at low tidesfrom June I980 to JuneI982 to graphresults for certainshorebirds knownto fly from Drake's Esteroto Abbott'sto roost at high tide (Fig. 3). Occurrencepatterns in the inshorezone are describedprimarily by histograms basedon censusesof the outer coast (see Figs. 5, 6, and 7). We present preliminarydata on winterpopulation trends at Bolinasand Limantour(see Fig. I4) that are part of ongoingstudies.

143 WATERBIRDS AT POINT REYES

Occurrencepatterns of very rare speciesrecorded on wetlandcensuses on Point Reyesare describedby either histogramssummarizing area-wide records (see Fig. 12) or by a summaryor listingof individualrecords. Histograms are basedon all recordsavailable through fall 1982, exceptthat CBC recordswere excluded to avoid the bias of intense observer effort each year during late December. Histogramsare basedon Point Reyesrecords only, except those for the Cattle Egret,Lesser Yellowlegs, Wilson's Phalarope, Parasitic Jaeger, and CommonTern, whichalso include additional Marin Co. recordsto givebetter definition to migratory periods. The graph of LesserGolden-Plover includes only wetlandcensus recordsand excludesrecords from upland habitatwhere migrantand wintering birdsmingle, blurring the boundariesof migratoryperiods. Listingsof recordsin the speciesaccounts include all data availablethrough fall 1988 and selecteddata throughspring 1989. Althoughwe occasionallyuse censusdata from Bodega Harbor in the speciesaccounts, we do not use them in describingoccurrence patternsof veryrare species. Peaksand troughsin the graphsof seasonalabundance (e.g., Fig. 4) enabled us to selectdates that independentlydefine each species'occurrence by fall, winter,spring, or summerperiods. We eliminatedthe tailsof peaksand troughs from the intervalsdefining periods to minimizethe effectof unusuallyearly or late influxesor departuresof birds on seasonalmeans. The dates used to define periodsfor each speciesare reportedin table4 of Page et al. (1983), whichmay be obtainedfrom the authorson request.From the seasonalmeans calculated for each year and site we derivedan averageabundance index expressed as birdsper 100 ha for the three main censusareas--Limantour, Bolinas, and Abbott's--combined. Followingthe approachof DeSanteand Ainley (1980), we useda loga- rithmic scale(base 4) to categorizeeach species'overall abundance in the three weftands as follows:

Very rare: lessthan 0.1 birdsper 100 ha Rare: 0.1-0.4 birdsper 100 ha Uncommon:0.5-1.6 birdsper 100 ha Fairlycommon: 1.7-6.4 birdsper 100 ha Common:6.5-25.6 birdsper 100 ha Very common:25.7-102.4 birdsper 100 ha Abundant:102.5-409.6 birdsper 100 ha The followingterms were used to categorizethe regularityof occurrenceof relativelyrare speciesin a geographicregion broader than the studyarea: Irregular:not recordedevery year but on averagerecorded more than onceevery 5 years. Casual:recorded on averageless than onceevery 5 years. Vagrant:a speciesfar from its normalrange of occurrence.This term alonedoes not indicateregularity of occurrencebut mustbe modifiedby one of the two previousterms, e.g., a casualvagrant to coastalCalifornia. The followingterms were usedto categorizethe seasonaloccurrence status of each species: Breeder:species confirmed as nestingin the studyarea by the presenceof active nests,flightless young, or recentlyfledged young with somedown remaining. Resident: species present continuouslythroughout a non-migratory period. Althoughsome individuals may stagein the area duringmigration, migrants are not sufficientlyabundant that their occurrencecan be detectedby a sub- stantialspring or fall peakin numbers.Resident does not implybreeding even

144 WATERBIRDS AT POINT REYES

when the classificationis as a year-round(winter and summer)resident or summer resident. Transient:species passing through the area duringmigration. In a givenseason, if numbersswell noticeably during migration periods, species that might other- wisebe classifiedas residentsmay be definedprimarily as transients. Dispersant:species that arrive in an areaafter a long-distancedispersal from their breedingsites. The timingand magnitude of occurrencevaries markedly from yearto year,probably in responseto fluctuatingfood supplies or markedvaria- tionsin reproductivesuccess. Visitant:species occurring intermittently in marginalhabitat or on the edgeof its normal range.

SPECIES ACCOUNTS

We describethe seasonaloccurrence patterns and abundanceof all speciesof aquaticbirds recorded on censusesof the Point Reyeswetlands in species accounts, except for Osprey, Bald Eagle, and Belted Kingfisher,which we arbitrarilyexclude. The accountsprovide information on inter-wetlandand year-to-yearvariation in occurrencepatterns, peculiaritiesof distributionon Point Reyes,historical population trends, sex- or age-relateddifferences in migrationaltiming or distribution,and habitat preferences. Seasonalabundance patterns in the Point Reyes area are compared to those on the rest of the California coast when these comparisonsare instructive.The northernCalifornia coast, from MontereyCo. north to the Oregonborder, is the most frequentframe of referencefor thesecomparisons; the centralCalifornia coast refers to the sub-areafrom Monterey Co. north to includethe countiessurrounding San Francisco Bay. Southern California is the area from San Luis ObispoCo. southto the Mexicanborder.

Red-throatedLoon (Gavia stellata) A rare summerresident and uncommonwinter resident(Fig. 4). High inshore summercounts off Drake'sBeach were 25 birdson 10 Jul 1977 (ABN: JVR) and 24 on 1 Jul 1981 (DS). The only suggestionof a peak of migrantson our cen- suseswas in Nov and Dec on inshorewaters (Fig. 5). Althoughlimited movement occursin Sep (ABN), fall migrationover inshoreand offshorewaters occurs primarilyfrom mid-Octto mid-Decwith peak movementin Nov (Cogswell1977, DeSanteand Ainley 1980, ABN). Away from the censusedwetlands, flocks of 200 to 800 birdsare reported alongthe Marin Co. shorelinein mostyears between late Dec and late Feb (ABN). Concentrationsare reportedmost regularlyat TomalesBay, where the high count was 2000 to 3000 birds on 27 Feb 1965 (ABN: JKe, TAC). We know of no other mid-wintergatherings of comparablesize elsewherein California. We sus- pect these birds are attracted to feed on spawning Pacific Herring (Clupea harenguspallasii) at the state'slargest runs just inside San Franciscoand Tomales bays(Spratt I98I). Spring migrationover neriticwaters extends primarily from late Mar to early Jun (ABN); peak migrationdates in centralCalifornia range from 17 to 21 Apr (ABN: BSa et al.). At Point Reyes,Red-throated Loons were foundin greatestnumbers in inshore waters(Table 1), deepbays, estuaries, and lagoons.They were rare in freshwater

145 COMMON LOON (L)

I JunI Ju I I AugI Sep I OctI No¾I Dec I JonI FebI,•3r I AprI M•YI IJunlJul I Aug[ SepI Oct [Nov I DecI Jan I Feb I Ma• I Apr I MayI

I JunI J u I I AugI SepI Oct It4ovI DecI JanI FebI MarIApr I Mayl IJunl Ju I I AugI $ep!Oct INav ID©cI JoeIF©b I MarI AprI MnI•I

I JunIJ u I I AugI SepI OctINov IDec I JanI FebI MorI AprI Mayl

PIED-BILLED GREBE (L) 43 43 11[ PACIFICLOON(A) 30 IJunlJul I AugI SepI OctINov I DecI JanI FebI MarI AprI • I 11[PAC(FIC LOON(B) IJunlJul IAugl SepI Oct INov IDec I JanIFeb I MarI AprI MayI

I Jun I J u I I AugI SepI Oct II•1ovI Pe½IJan I Feb I •or I Apr I MayI

IJunlJul I AugI SepI Oct I NovI DecI Jan I FebIMar I Apr I MayI JJun [ J u [ [ At• I SepJ Oc* I NovJDec I JoriJ Feb [ A•:•FJ•pr JMay !

. I JunI J u I I AugI Sepl Oct INov IDec I JanI FebI MarIApr I Mayl

I JunI J u I I AugI SepI O½lINov IDec I Jan I FebI •ar I Apr IMayl

COMMON LOON (B)

I J•n [ Ju II Aog[ SepI OctINov I DecI JanI FebI MarI AprI Mayl I JunI J u I IAugI Seploot INov IDec I Jan IFeb IMar I Apr[Mayl

Figure 4. Seasonalabundance of some loons and grebesin wetlandsof Point Reyes. The top of each verticalline representsthe maximumnumber counted on any censusduring the correspondingthird of a month,the bottomof eachvertical line representsthe minimum numbercounted on any censusduring the correspondingperiod, and the horizontalline is the mean for the correspondingperiod. Maxima exceedingthe scaleon the graphare indicatedby arrowsand the appropriate number. A, Abbott'sLagoon; B, BolinasLagoon; L, LimantourEstero. WATERBIRDS AT POINT REYES

ponds, lakes, and reservoirs,but more frequent there during migrationthan at other times. Duringmigration, Red-throated Loons occupy ocean waters closer to shore than do Pacificand Common loons, and duringwinter they are closerto shorethan are Pacifics(Briggs et al. 1987). PacificLoon (Gauiapacifica) A rare summerresident, rare fall transient,very rare winter resident,and rare springtransient (Fig. 4). Althoughthousands of PacificLoons fly by Point Reyes duringspring and fall migrations,few pausehere. Peak inshorenumbers were recordedin Jul and Aug (Fig. 5). At that time the specieswas rare or absenton the wetlands (Fig. 4), except at Limantour, where birds move into the estero mouthfrom Drake'sBay. From Jul to Sep high single-observercounts for inshore watershave rangedfrom about 30 to 85 birds(ABN) with a maximumof 170 on

RED-THROATED LOON HORNED GREBE

BLACK BCOTER II

SURF )TER PACIFIC LOON 5001

o,.lil,_11 II o .i ß I 200(]oo,

COMMON LOON WESTERN/CLARK'BGREBE100(] •ooo• . I

WHITE-WINGEDSCOTER

30 2000I

- ooo0 Lf SON0 J FMAMJA MA J AS SOND J F •J AS

Figure 5. Seasonalabundance of loons, grebes,and scotersin the inshorezone along the southerncoast of Point Reyes (see Fig. 1) from September 1980 throughSeptember 1981 (therewas no June 1981 census).Solid bars, identified birds; open bars, unidentifiedbirds, proportioned among the identified as described under Methods.

147 WATERBIRDS AT POINT REYES

TaBle I Comparisonbetween Inshore and EstuarineAreas of Monthly Counts of Waterbirds,November 1980 to March 1981 ø

Inshore Estuarine

Species M SE Range M SE Range

Red-throated Loon 98 10 60-118 5 1 1-7 Pacific Loon 20 6 1-36 2 2 0-8 Common Loon 51 7 33-72 18 4 8-28 Loon spp. 81 31 15-84 ------Red-necked Grebe 64 12 31-107 1 t, 0-1 Horned Grebe 120 36 51-256 245 30 201-327 Eared Grebe 42 12 16-74 328 107 181-746 Western/Clark's Grebec 4498 994 506-6799 76 6 61-91 Black Scoter 29 4 20-45 ------Surf Scoter 2836 419 1608-3778 737 101 547-1004 White-winged Scoter 158 29 71-251 269 46 148-418 Scoter spp. 850 96 594-1088 ------

Estuarinecounts combined for three estuaries;inshore counts combined for 10 sub-areas(Fig. 1). See Methodsfor correctionsfor smallnumbers of unidentifiedbirds. M, mean number of birds for 5 counts; SE, 1 standard error. Value of 0.2. PredominantlyWestern Grebe (seespecies account).

Drake'sBay on 1 Sep 1980 (DS). Alongthe centralCalifornia coast fall migration extendsfrom mid-Octthrough Dec with peak movementfrom Nov to earlyDec (ABN, Cogswell1977, DeSante and Ainley 1980). However, sometimesthou- sandsof birdscan stillbe seenflying south past Point Reyes from mid-to late Dec (AB 33: 309, 35: 331). Althoughgenerally much lessnumerous in Californiaafter Dec (Briggset al. 1987), PacificLoons occupy sheltered coastal waters then and concentrate locally, apparentlyto feed on spawningPacific Herring. High mid-wintercounts are of 2000 birdsflying north at Bolinason 6 Jan 1977 (AB 31: 367), 2500 to 2800 off Muir Beachon 4 Feb 1978 (JGE),and about6300 just north of the Golden Gateon 3 Jan 1983 (BB). Springmigration over neritic waters extends primarily from late Mar to earlyJun (ABh0;peak migration dates in centralCalifornia range from 21 Apr to 6 May (ABN: BSa et al.). The end of springmigration was difficultto define. Recordssuch as that of 300 to 1000 PacificLoons at Drake'sBay between 18 and 24 Jun 1982 (AB 36: 1011, ABN) may have represented summerstragglers, since numbers typically dwindled later in the summer(Fig. 5). PacificLoons occurred in greaternumbers in the inshorezone than in the estuaries(Table 1). In the inshorestudy area they usuallyconcentrated in Drake'sBay (Fig. 6). Althoughoverlapping with the other loonsin habitatchoice, Pacifics tend to occupydeeper coastalwaters and migratefarther from shore (Briggset al. 1987). In northernCalifornia they migrateprimarily over the continentalslope within 50 Panof shore,but alsoover the continentalslope up to 110 km from shore(Bfiggs et al. 1987). Duringmigration in Apr 1986 they were seenfeeding with Common Murres65-80 km off Point Reyes(D. G. Ainley pers. comm.). 148 WATERBIRDS AT POINT REYES

Pacific Loons occur rarely along the coast on freshwaterlakes, reservoirs,and ponds,especially during migration (ABN, pers.obs.).

Common Loon (Gayla iramet) A rare summer resident, uncommon fall transient and winter resident, and fairly common spring transient(Fig. 4). Numbersin neritic waters in Jul were amongthe highestof the year,whereas from Jun to Aug estuarinenumbers were the lowest(Figs. 4 and 5). The highestsingle-observer summer count was of 76 birdsin Drake'sBay on 28 Jul 1980 (AB 34: 925). A high fall countwas of a flock of 150 off Bolinason 16 Oct 1976 (JGE). Althoughlimited data from the PacificCoast suggestsome southwardmovement from mid-Sep to Oct (Palmer 1962, ABN), fall peaksat Abbott'sand Limantourindicated a mid-Oct through earlyDec passageas at the Farallones(DeSante and Ainley 1980). Althoughnot evidentfrom our censusesof birds on inshorewaters (Fig. 5), Common Loons migratein fall overneritic waters off Californiafrom late Oct to mid-Dec(Briggs et al. 1987). Common Loons migratein springover neriticwaters primarilyfrom late Mar throughMay (ABN); peak migrationdates in centralCalifornia range from 12 Apr to 6 May (ABN: BSa et al.). Peak springnumbers in Point Reyeswetlands were foundin Apr and May (Fig.4). CommonLoons use estuaries, lagoons, larger bays, and inshorewaters. They were more evenlyspread between estuarine and inshorehabitats than the other loons(Table 1, Fig. 6); inshorethey were concentratedin Drake's Bay (Fig. 6). The speciesis also found on the coast in small numbers on freshwater lakes, ponds,and reservoirs(ABN, pers.obs.).

Pied-billedGrebe (Podilymbus podiceps) A rare summer residentand fairly common winter resident exhibitingno migratorypeaks (Fig. 4); smallnumbers nest at scatteredsites in the studyarea and elsewherein Marin Co. (PRBO unpubl.data). Decliningearly winter numbers at the wetlands(Fig. 4) may have partly reflectedshifts of birds to freshwater habitatnewly available or enhancedas a resultof winter rains. The broadoverlap of the breedingand winteringrange and the species'nocturnal migratory habits (Palmer1962) make it difficultto define migrationperiods. A Sep to Nov fall migrationwas indicatedby increaseson the wetlands(Fig. 4). Althoughmost closelyassociated with freshwaterponds, Pied-billed Grebes at Point Reyesalso use bays, estuaries, lagoons, and, rarely,inshore neritic waters in the non-breedingseason. They breedhere on freshwaterponds with much shore and emergentvegetation or in marsheswith some open water.

Horned Grebe(Podiceps auritus) A very rare summervisitant and a commonwinter resident(Fig. 4). Two birds at Limantouron 16 Jul 1975, one to two at Abbott'son six dates from 5 Jun to 25 Jul 1980, three at Drake's on 23 Jun 1980, and one at Bolinason 24 Jun 1981 were the only summercensus records. Repeatedsightings of one to two birdsat Drake'sBay from 5 to 20 Jun 1980 and 6 Jun to 18 Aug 1981 (DS) demonstratedoccasional oversummering on inshorewaters. Migrationspanned lateSep to Dec in fall andMar to earlyMay in spring(Figs. 4 and 5). Horned Grebesuse estuaries,lagoons, and inshorewaters in preferenceto freshwaterhabitats. In ourstudy area Horned Grebes occurred in greaternumbers in estuariesthan in inshorewaters (Fig. 7, Table 1), where most birdswere found in Drake'sBay (Fig.7). HornedGrebes outnumbered Eared Grebes by almost3 149 WATERBIRDS AT POINT REYES

2.01

AREAS 6-10 Sep-Oct ESTUARIES 1.0 AREASI-5

o 2.0 Nov-Jan

Feb-Apr

o 2.0

May-Jun 1.o

Common Pacific Red-throated

Figure 6. Densitiesof positivelyidentified loons in estuariesand along two stretchesof the southern coast of Point Reyes. See Fig. 1 for sub-areas. Estuarinevalues are for BolinasLagoon, LimantourEstero, and Drake's Estero combined.

150 WATERBIRDS AT POINT REYES

to 1 in the inshorestudy area in winter, whereasat the Farallonand Channel islands,Horned Grebes are vastlyoutnumbered by EaredGrebes (DeSante and Ainley1980, Briggset al. 1987). Cogswell(1977) reportedthat HornedGrebes havebecome increasingly common in coastalCalifornia since 1930.

•o 200 Western/Clark'sGrebe

e ß ß - •oo Sep-Oct 30 JRed-necked HornedGrebeGrebe oß _ _ _ Bß B ß. ß ....

200

• •o • Nov-Jß • • ,oo o _• ß_B ß - • I EaredGrebe '• Feb-A

L D P I 2 3 4 $ G ? g 10 Sub-Are•s---- "-- 0• -- I -- -- • • ' -- -- Sub-Areas

Surf Scorer

•øøo...... I Sep-Oct m White-wingedScorer 2o0 Sep-Oct Nov-don I J lOO 20 I J __JNov-Jan

" '"' g • • I Feb-A.r

May-Jun

•' B L D P 1 2 3 4 5 6 7 8 g 10 P 1 2 3 4 5 6 7 8 g 10 •ub-Areas •ub-Amas

Figure7. Densitiesof grebesand scoters along the southerncoast of PointReyes. The numberedsub-areas are shown in Figure1. B, BolinasLagoon; L, Limantour Estero;D, Drake's Estero;P, HorseshoePond. 151 WATERBIRDS AT POINT REYES

Red-neckedGrebe (Podiceps grisegena) A very rare estuarinewinter residentwith 18 birdson 32 censusdates from 23 Sep to 8 May; 12 of the 18 were at Limantouron 25 dates. Repeatedsightings of one to two birds in the inshore zone off Drake's Beach from 6 Jun to 20 Jul 1980 (ABN), from 6 Jun to 31 Jul 1981 (ABN), and from 18 Jun to 9 Jul 1983 (AB 37: 1022) representedoversummering birds. A bird at LimantourEstero on 10 and 16 Jul 1975 (AB 29: 1025, ABN) wasthe only one foundin an estuaryin summer. In 1981 in Drake'sBay, 3 birdson 4 Aug (ABN: DWm), 7 on 15 Aug (AB 36: 212), and 21 on 17 and 18 Aug (Fig. 5) suggestedthat fall arrivalbegins in early Aug and that numbersincrease through the month. High inshorecounts of 78 birdsin Sep and 107 in Mar (Fig. 5, Table 1) were duringfall and spring migratoryperiods. Althoughour data suggestedfall movementfrom Aug to Sep, Palmer's (1962) statement that "nearly all birds are on salt water by mid- November"suggests a more protractedmigration. Our Mar peak, the occurrenceof 15 birds on Drake's Bay on 7 May 1981 (Fig. 5), and the paucityof late May and earlyJun recordsfor northernCalifornia (ABN) suggestthat springmigration extends from Mar to early May. Red-necked Grebesare scarcediurnal migrants over inshorewaters of the centralCalifornia coast in spring, from at least 11 Mar to 5 May (ABN: BSa et al.), becausethe speciesis very rare in southernCalifornia (Garrett and Dunn 1981) and mostbirds probablymigrate at night (Palmer1962). Red-neckedGrebes are generallyconsidered rare in California(Grinnell and Miller 1944, Cogswell1977, McCaskieet al. 1979), but at leastlocally in inshore watersat Point Reyestheir numberswere similarto thoseof the other grebesand loons,except for the abundantWestern Grebe (Table1). We foundno reference to numbers of Red-necked Grebes consistently this high elsewhere on the California coast. Virtually all Red-neckedGrebes recorded on inshorecensuses were in Drake's Bay (Fig. 7, Table 1), but they also congregatedat the mouth of TomalesBay, wherethere were sightingsof 45 birdson 22 Dec 1973 (ABN: SFB) and 37 on 9 Jan 1978 (DS). AlthoughRed-necked Grebes at Point Reyesinhabit mostlyinshore waters and the mouthsof deeperbays, they sometimesalso occupy estuaries,lagoons, and, occasionally,brackish streams (DS) or freshwaterponds adjoiningmarine waters (fide J. Morlan).

Eared Grebe (Podicepsnigricollis) A very rare summervisitant and commonwinter resident(Fig. 8). The only summer censusrecord was of one bird at Abbott's on 29 Jun 1976. At Abbott's, where Fared Grebeswere mostnumerous, the fall build-upwas protractedand the springdecline was rapid(Fig. 8). None of the wetlandsexhibited migratory peaks (Fig. 8). Exceptfor the low Feb numbers(see Methods), seasonal use of inshore waterswas similarto that in the estuaries(Figs. 5 and 8). Our evidenceof protractedfall migration(Fig. 8) is supportedby the pattern inlandat Mono Lake, wherenumbers in fall beginto buildup in late Jul and peak in mid-Oct;large numbers may remain until at least late Dec in some years (Jehl 1988). In San FranciscoBay salt ponds,where greater numbers "winter" than on Point Reyes, the populationincreases throughout the fall and winter and peaksin Apr (Swarth et al. 1982). This may reflectthe overlappingof birdsfrom the protractedfall migrationwith thosefrom springmigration, which extends from Mar to mid-May (Palmer 1962, Jehl 1988). In our studyarea FaredGrebes used estuaries and lagoonsmore than inshore waters(Table 1, Fig. 7), wherethey concentratedin Drake'sBay (Fig. 7; seealso HornedGrebe). FaredGrebes were also numerous on freshwaterponds. WATERBIRDS AT POINT REYES

GREBE (A)

1EARED tt I JunI Ju I IAugl Sepl Oct INov IDec I JanIFeb IMar I AprIMayl 500 1300 I JunIj u I I AuglSepl Oct INov IDec I JanI FebI MarI AprI Mayl

BROWN PELICAN (A)

IJunlJu•I AugI SeplOct I Nov IDec I JonI FebI MarI AprI May'

I JunI Ju I IAugl SepI OctINov IDec I JoriI f:ebI MorI AprI MayI

BROWN PELICAN (B)

I JunI Ju I I AugI Sep I OctI NovIDec I JoriI Feb I MarI AprI MayI :f •[ WESTERN/CLARK'SGREBE(k) BROWNPELICAN (L) I JunI J u I I AugI $ep I OctIfqo¾ IDec I JonI f:eb I Mor IApr I Mayl IJunlJul I AugI Sep I OctI NovI DecI JonI FebI MarI AprI &tz/I

Figure8. Seasonalabundance of somegrebes and pelicansin weftandsof Point Reyes. See Figure4 for details. 153 WATERBIRDS AT POINT REYES

Western Grebe (Aechmophorusoccidentalis) and Clark's Grebe (A. clarkii) We did not distinguishWestern and Clark's grebes,formerly thought to be morphs of a singlespecies, on our censuses. Aechmophorusspp. were rare summer residents,common fall transients,and fairly common winter residents (Fig.8). Fallmigration extended primarily from Sep to Dec (Fig.8) and perhapsto Jan (Fig. 5). Briggset al. (1987) alsorecorded peak numberson inshorewaters alongthe Californiacoast from Nov throughJan. A fall peak at Abbott'sand Limantourwas followedby a gradualdecline in numbersthrough the winter,while at Bolinasno fall peakwas evidentand numbersremained relatively stable through the winter(Fig. 8). Seasonaluse of inshorewaters was similarto that of the estuaries, except that inshore waters supporteda large oversummeringpopulation (Figs.5 and 8). Spring movementextends from late Mar throughMay (Palmer 1962, Figs. 5 and 8). Aechmophorus spp. were found in much larger concentrationsin inshore waters than in estuaries,lagoons, or ponds (Fig. 7, Table 1); inshore concentrations shiftedseasonally (Fig. 7). Overall, Aechmophorusdensities were the highestof any waterbirdin our inshorestudy area. These birdsprefer waters within 0.5 km of shoreover sandybottom lessthan 10 m deep, especiallydown- wind from major headlands(Briggs et al. 1987). Western Grebes are much more common in this area than Clark's Grebes. Counts in Jan 1977 showed 88.4% of the birds in California and Nevada to be Westerns;at the two Marin Co. sitesclose to our studyarea 87.1% of the birds were Westerns(Ratti 1981). Also, at least90% of 280 birdsin Drake'sBay on 18 Apr 1980 were Westerns(JGE). Both Westernand Clark'sgrebes oversummer on coastalwaters, with the former predominating(ABN). AshyStorm-Petrel (Oceanodroma homochroa) A very rare visitantwith one censusrecord of a single,apparenfiy healthy, individualfound inside Bolinas Lagoon on 21 Feb 1977 (AB 31: 368). For much of the year this speciesinhabits pelagic waters off Californiafrom the continental shelfedge to 25 km seaward,particularly on the warm sidesof thermalfronts bor- dering upwellings(Briggs et al. 1987). A few Ashy Storm-Petrelsbreed in our studyarea on Bird Rock, TomalesPoint; over 75% of the world'spopulation breedsnearby on the Farallones(SowIs et al. 1980). Off centralCalifornia peak numbersoccur from Sep to Jan; an increasein sightingsseaward of the continentalslope after Dec suggeststhat many birdswinter in deeperwaters (Briggs et al. 1987). Stragglersinside San FranciscoBay and casualtieson city streetshave invariablybeen immaturebirds (D. G. Ainley pers.comm.). AmericanWhite Pelican(Pelecanus ewthrorhynchos) A fairlycommon winter resident(Fig. 8). A summeringbird on Drake's Estero from 8 Mar to 8 Jul 1965 was apparentlyinjured (PRBO). There appearsto be no regularmovement along the coast;instead, birds move direcfiy overland to and from inlandbreeding sites. Birdsfrom Drake'sEstero use Limantourerratically, explainingthe gaps in the Limantour graph. Censusesat Limantour reveal the normaltiming of sightings,early Aug to late Jan (Fig. 8), but not the Oct to Jan periodof peak numberson Point Reyes(pers. obs.). Earliestand latestnon-census records,respectively, were 17 Jul 1983 (RMS) and 3 Feb 1981 (DS), exceptfor 21 birdson TomalesBay on 24 May 1988 (ABN: RHa), 61 there on 2 June 1988 (TNo), a number there on 12 June 1989 (TNo), and 7 at Bolinason 27 Jun 1989 (KH). These May and June sightingsparalleled widespread reports at that time in

154 WATERBIRDS AT POINT REYES

the San FranciscoBay Area (AB 42: 477, ABN), and particularlyhigh numbersin that seasonin 1988 may have reflectedbreeding failures inland followingthe 1986-89 drought. From 1970 to 1988 the mediannumber of Vv'hitePelicans recordedon the Point ReyesCBC was 77 (range6-827); the high countis likely an overestimatedue to duplicate counts of conspicuoussoaring flocks. The highestnon-census count at a singlelocation was 360 at Limantour on 19 Dec 1971 (CBC data fide BiL). White Pelicans'occurrence on Point Reyesis generally brieferthan on San FranciscoBay, where smallnumbers occur irregularly through the spring,non-breeders may arriveas early as mid-May,and substantialnumbers may buildup by late Jun to earlyJul (ABN). On Point ReyesWhite Pelicansuse shallowestuarine waters and, to a limited extent, freshwaterponds. Most birdsaggregate in Drake's Esteroand near the mouth of TomalesBay, perhapsbecause suitable fish prey concentratein the extensiveeelgrass beds at these sites. White Pelicansirregularly used Bodega, Abbott's,and Bolinas,in descendingorder of frequency. The sandspitat the mouthof Drake'sEstero, the mouthof WalkerCreek on TomalesBay, and Bird Rockoff TomalesPoint are traditionalroosting sites. Habitat lossand disturbancereduced overall numbers and breedingsites in Californiafrom the 1880s until the late 1950s (Grinnelland Miller 1944, Remsen 1978). This declineparalleled a reductionin the numberof breedingcolonies throughout the western U.S., with numbersstabilizing in recent years (Sloan 1982, Smith et al. 1984, Sidleet al. 1985). Thesedeclines suggest that numbers of White Pelicanswintering on the Californiacoast have also decreasedhistori- cally.

Brown Pelican (Pelecanusoccidentalis) A very common summerto early winter dispersantand a very rare late winter to springvisitant (Fig. 8). Seasonalmovements of Brown Pelicans,and a number of otherseabirds, are stronglyaffected by seasonalcycles of upwellingand temper- aturechanges in the CaliforniaCurrent (see below and Resultsand Discussion).At Point Reyes Brown Pelicans were most numerous at Bolinas, where numbers increasedfrom Jun to Aug, peakedfrom lateJul to earlyOct, and declinedsharply thereafter(Fig. 8). Althougha few birdswere presentat Abbott'sby Jun, numbers there did not increasemarkedly until Aug. Brown Pelicansvisited Limantour errat- ically. In neriticwaters, however, Brown Pelicans frequently may be foundearlier and later in the year than in Point Reyesestuaries. Birds dispersing north typically begin to trickle into San FranciscoBay and neriticwaters north of Montereyin May, rarelyin Apr, or exceptionallyin Mar (ABN);they arrivelater farthernorth (Andersonand Anderson 1976, Henny and Collins 1980, Briggs et al. 1983). Overall on the central Californiacoast, pelicannumbers peak in Sep and Oct (Briggset al. 1983). In neriticwaters of this regiona secondarypeak occursin Nov and Dec, but the birdsdo not fly consistentlysouth, as wouldbe expectedof a rapid, directedmigration. Stragglersare usuallyseen in neritic waters through Jan, and occasionallysmall numbers remain through winter and spring, as in 1977-78, 1983-84, and 1987-88 (AB 32:394 and 1050, AB 38: 352, Briggs et al. 1983, AB 42: 314). A few stragglerssometimes use BolinasLagoon in winter as well. The timing of arrival in northern Californiavaries annually as a functionof variationin the seasonalwarming of the oceansurface (Anderson and Anderson 1976; Briggset al. 1981, 1983). While the timingof peak numbersis correlated withtiming of peakmean sea surface temperatures south of PointReyes (Briggs et ai. 1983), the magnitudeof the peak appearsto be relatedmore to preceding events at breedingcolonies in the Gulf of California (Andersonand Anderson

155 WATERBIRDS AT POINT REYES

1976, Briggs et al. 1981, 1983). The pelicans' northward dispersallags well behindthe warmingtrend (Briggset al. I98I), as wouldbe expectedfor a species respondingto fish productivity.Exceptionally early dispersal is often precededby breedingfailures in the Gulf of Californiarelated to unusuallywarm water along the PacificCoast, which, in turn, often correspondsto intenseE1 Nifios off South America(Anderson and Anderson1976). Earlyarrivals at Bolinasof 44 birdson 7 May 1973 and 8 birdson 28 Apr 1983 (JGE)heralded very earlybuild-ups of numbersalong the northernCalifornia coast in [] Nifio years(AB 27:814 and 912; AB 37: 907). Countsoff Bolinasof 6 birdson 24 Apr and 35 on 26 Apr 1987 (RMS) and 450 on 30 Apr 1989 (ABN: PEG) also coincidedwith early build-upsalong the northernCalifornia coast (AB 4I: 483, ABN) in non-ElNifio, thoughwarm-water, years. The departureof BrownPelicans to the southin early wintercoincides with a periodof dwindlingfood resources,but departureat that time is perhapsmore stronglyinfluenced by stormy weather (D. W. Anderson pers. comm.). At BolinasLagoon marked year-to-year variation in the timingof peak numbers (Fig. 9) was causedto some extent by pelicansconcentrating to prey on Northern Anchovies(Engraulis mordax), which also migrate seasonallynorth to centralCalifornia (Mais I974, Parrishet al. I981) and move in and out of bays and estuaries(Richardson I980). The highest pelican counts in our study area--6000 birdsinside Bolinas Lagoon on 7 Sep I984 (}{MS),9000 in Bolinas Lagoonand BolinasBay on 8 Sep 1984 (DGA, RF), and 3800 in BolinasLagoon on 24-25 Aug 1985 (RMS)--were recordedduring large anchovy runs. Overallin centralCalifornia, pelicans concentrate from PointLobos to Bodega at traditional, safe roosts near optimal foraging areas (Briggs et al. I98I). Traditionalpelican roosts in the Point Reyesarea are on tidal fiats,sand spits, and large offshorerocks. Foragingbirds frequent estuaries, lagoons, and inshoreand offshorewaters (mosfiy within 20 km of shore),particularly where plumes of cool, upwelledwater intrude into warmer,more stratified water of the CaliforniaCurrent (Briggset al. 1983, 1987). Andersonand Gress(I983) summarizedpopulation trends, showing a drastic declinefrom I969 to I973, coincidingwith high DDT levelsthat affectedrepro- ductivesuccess in pelicanpopulations in southernand Baja California,and an increasefrom 1974 to 1980, as pollutionlevels declined. By the mid-1980sthe southern California breedingpopulation appeared to have reached historical levels,but the speciesis stilllisted as endangeredby stateand federalgovernments (D. B. Lewis pers. comm). We did not detect any consistentfrends in pelican numbersover the courseof our study,perhaps because of the markedyear-to-year variabilityin numbersand the localextent of our censusefforts (see Briggs et al. 1983). Double-crestedCormorant (Phalacrocoraxauritus) A fairly commonsummer resident, common fall transient,and fairly common winter resident(Fig. I0). High Aug to Dec numbersat wetlandscorresponded with post-breedingdispersal of adultsand •1oungfrom the nearbyFarallon Islands (Boekelheide,Ainley, Huber, and Lewis in press),as evidencedby sightingsof Farallon-bandedbirds at Bolinas Lagoon, Drake's Estero, Tomales Bay, and Abbott'sLagoon (ibid, DS pers.ohs.). Migrationof inlandbreeders to the coast (SowIset al. 1980) or the dispersalof other coastalbreeding populations may also contributeto the fall peak. AlthoughFarallon-banded birds have been recovered from BritishColumbia to San Diego, with the majorityfound along the central Californiacoast, overall there is a southwardtrend to dispersal,especially among first-yearbirds (Boekelheide, Ainley, Huber, and Lewis in press). Since Double- crestedCormorants are essentiallyabsent from the Farallonesfrom Sep untilmid- 156 WATERBIRDS AT POINT REYES

Mar (ibid), the Jan declinein weftandnumbers may havebeen due to birdsmoving to increasedfreshwater habitat following heavy winter rains. Notable spring migratorymovement was indicted by flocksof about1000 flyingup the westshore of TomalesBay on 8 and 9 Apr 1986 (AB 40: 519). Although some Double-crested Cormorants on Point Reyes estuaries in summerare Farallonbreeders on foragingtrips (Boekelheide,Ainley, Huber, and Lewisin press),many othersare immaturenon-breeders. Recenfiy the specieshas been discoverednesting on the Richmond-SanRafael and Oakland-SanFrancisco (Bay)bridges (AB 38: 1057). Birdsfrom thesecolonies may ventureoutside of San FrancisoBay on occasion,but probablymost breeding birds in summerin the Point Reyesarea originatefrom the FarallonIslands.

ß 2500 8oo

: : 600 **l I .i I 400 • :r •1 lb, I k'' .. :: :ll•

.I I.l i II _ ß I .• , '.••

Figure9. Numbersof BrownPelicans at BolinasLagoon during 1973 (dottedline), 1974 (brokenline), and 1975 (solidline).

157 WATERBIRDS AT POINT REYES

In the Point Reyesarea Double-crestedCormorants forage in estuaries, lagoons,bays, and largeponds; they occuronly rarely here in inshorewaters.

DOUBLE-CRESTED CORMORANT (A)

IJunlJulI Aug I Sep I Ocl INo¾ IDec I Jon I Feb I Mar I Apr I May I I JunI Ju I I AugI Sep I OclINov I DecI JonI FebI MorI AprI MayI

I J•nI J• I I Augl$:pl OcliNov I D:c I J•nl FebI MorI kPrI MayI

DOUBLEICRESTED CORMORANT (L) IJunlJulI AugI Sep I OctI NovI DecI JonI FebI MarI AprI MayI

o,,..:.,.:.:.1:...,I., .L,.I ..... I JunI Ju I I AugI seplOct INov Ioec I JoriI FebI MotI AprI May1 SNOWYEGRET(A) I JunI Ju I IAuglSep I Oct INov IDec I Jon I Feb I Mor I Apr I May J

Ijun IjI u I IAug I Sep IOct INov IDec I Jon IFeb IMar IApr IMayl•

I JunI Ju I I AuglSepl Oct INov I DecI JanlFeb I MarI AprI NtaYI

o SNOWY EGRET (L) l jun I j u I l Augl$:pl Ocli NovID:c I Jonl F•bIMor I Ap:l Mayl .,.•. .:..I. ß, II.::,ll..l-'l'-[-l-'[.,.t'•] ß.: .,.: l JunI Ju I IAugl$:pl OctINovID:cl JonI F:b IMarI AprI Mayl GREATBLUEHERON (L)

I JunI Ju I I AugI SeplOct INov IDec I JonlFebl Mot IApr I MayI BLACKICROWNED NIGHT-HERON (B)

O•EIT EO•ET

l JunIJ u I l•l sepl ocll•l[ec I JanIFeb I •r Ikpr I • I IJunlJul l AugI S:p I Ocli Novl[:c I JanIF:b I MarI kpr I MayI

Figure 10. Seasonal abundance of the Double-crested Cormorant and some heronsand egretsin wetlandsof PointReyes. See Figure4 for details. 158 WATERBIRDS AT POINT REYES

They often roost on sandbars,small islands, and pilings. A few alsoroost during the day on somecoastal rocks and reefs,and manyroost at nighton Bird Rockoff TomalesPoint (DS). They foragefor schoolsof fish "from the surfaceto near,but not on, bottomshaving no relief"(Ainley et al. 1981). Double-crestedCormorants formerly bred on coastalbluffs at Point Resistance just north of Bear Valley(L. P. Bolanderand Bryant 1930). Althoughthey have not bred recentlyanywhere along the Point Reyesshoreline (SowIs et al. 1980, authors'pers. obs.),they do breedon offshorerocks, cliffs, and man-madestruc- tures at scatteredsites elsewherealong the California coast (SowIset al. 1980, ABN). Becauseof variousdisturbances, breeding populations at the Farallones (Ainleyand Lewis 1974), on islandsoff southernCalifornia and Baja California (Gresset al. 1973), and in interior California (Grinnell and Miller 1944, Reinsen 1978, SowIset al. 1980) have declinedsteeply. Ainley and Lewis(1974) argued that the failureof marinebreeding populations to recoverfrom their declinewas due to the crash in the late 1940s of the PacificSardine (Sardinopscaerulea) population,apparently caused by overfishingat a time of unfavorableenviron- mental conditions. Human disturbanceon the Farallonesundoubtedly continued to keep numbersdown, but with protectionthe populationhas increasedmodesfly sincethe early 1970s (Boekelheide,Ainley, Huber, and Lewis in press). Other increaseson AnacapaIsland off southernCalifornia (Anderson and Gress1983), in San FranciscoBay, and for California as a whole (USFWS Breeding Bird Surveysfide Sam Droege)indicate a trend of widespreadrecovery of breeding populationsof Double-crestedCormorants.

Brandt'sCormorant (Phalacrocorax penicillatus) Brandt'sCormorants nest regularlyon offshorerocks and coastalbluffs in our studyarea and all alongthe Californiacoast, including the FarallonIslands, where 45% of the total Californiapopulation breeds (SowIs et al. 1980). They were very rare fall and wintervisitants to the estuaries(Fig. 11). The scarcityof springand summer estuarinesightings coincided with the occupationof nearby nesting colonies;more numerousfall sightingscoincided with the dispersalof juveniles (Boekelheide,Ainley, Morrell, and Lewis in press). Our data for inshorewaters were not adequate to explain seasonalmovements, especiallysince Brandt's Cormorantsare highlymobile when feeding(PRBO unpubl.data). After dispersal from nearby breeding areas, Brandt's Cormorants were least abundant in our inshore study area from Dec to Apr, a pattern similar to that for the central Californiacoast overall (Briggs et al. 1987). Farallonband recoveriesshow an Aug to Nov northwardmovement by juvenilesand, to a lesserdegree, by adults (Boekelheide,Ainley, Morrell, and Lewis in press). Movement to the south, as earlyas Sep (Briggset al. 1987), leavesthe winter populationspread out alongthe entireCalifornia coast with the bulkof the birdsin the centralregion (Briggs et al. 1987, Boekelheide, Ainley, Morrell, and Lewis in press). Garrett and Dunn (1981) reported a northward movementin Feb and Mar in Santa Barbara Co. Brandt'sCormorants prefer neriticwaters mostly within 10 km of shoreand 25 km of roostsand colonies(Briggs et al. 1987); they are rarely found in the small estuariesand lagoons(Fig. 11). Large numbersoccur regularlyin San FranciscoBay, and seasonallyin TomalesBay duringwinter herringruns. They feed primarilyon both schoolingand non-schoolingfish on or just aboverocky, sandy,or muddybottoms, though they alsocatch appreciable prey from middle depthsto the surface(Ainley et al. 1981). The Farallonnesting population was decimatedby commercialegg collectorsin the 1800sbut has recoveredrapidly sincethe 1920s (Ainleyand Lewis 1974).

159 WATERBIRDS AT POINT REYES

PelagicCormorant (Phalacrocorax pelagicus) PelagicCormorants breed regularly on rockycoastal cliffs in our studyarea and all along the Californiacoast (SowIs et al. 1980). They foragein inshorewaters, mostlywithin 10 km of land(Briggs et al. 1987), and in the mouthsof deepbays. They were very rare visitantsto the wetlandsfrom Sep to earlyJun (Fig. 11). The greaterincidence of fall sightingscoincided with dispersalfrom breedingsites. Informationon seasonalmovements is scanty(Boekelheide, Ainley, Huber, and Lewis in press). Garrett and Dunn (1981) reportedincreased numbers south of San Luis Obispo Co. from mid-Sep to late Apr, indicatingthat some Pelagic Cormorants move south in winter (Garrett and Dunn 1981), but Briggs et al. (1987) didnot noteany seasonalmovements. Although Pelagic Cormorants often feedon solitaryprey that hide in rockyreefs (Ainley et al. 1981), Farallonbreeders are strongly dependent on mid-water schoolingrockfish (Sebastes spp.)

1,5

BRANDT•S CORMORANT

0,0

PELAGIC CORMORANT :::)

z ILl

MONTH

Figure 11. Mean numberof Brandt'sand Pelagiccormorants per censusfor }]olinasand Abbott'slagoons combined. 160 WATERBIRDS AT POINT REYES

(Boekelheide,Ainley, Huber, and Lewis in press). Breedingpopulations declined drasticallyat the Farallonesduring the 1800s becauseof disturbancefrom commercialegg collectorsbut haverecovered slowly since the early 1900s (Ainleyand Lewis 1974).

Great Blue Heron (Ardea herodias) A fairlycommon year-round resident (Fig. 10). Sincethere is littleevidence for migrationaway from coastalCalifornia (Palmer 1962, Gill and Mewaldt 1979), seasonalchanges in abundanceare bestexplained by localmovements. Variation in numbersat Bolinas (Fig. 10) correspondedwith breedingat the Audubon Canyon Ranch rookeryon the east sideof the lagoon. The mediannumber of adultGreat Blue Herons nesting at AudubonCanyon from 1967 to 1981 was90 birds(range 54-124; Pratt 1983). Birdsbegin occupying the rookeryin late Jan or early Feb and commencenesting shortly thereafter (Pratt 1970, 1972a,b). Initiationsof first clutchespeak in mid-Mar(Pratt 1974); heron numberson the lagoon then droppedwhile one of each pair was incubating. At this stage of nestingPratt (1980) found that 45% of the departingherons went to Bolinas Lagoon to forage, while the otherswent elsewhere. The Jun peak on Bolinas Lagoon occurredwhen most chicks,at that time at least 3 weeksold, are first left unattendedfor part of the day (Pratt 1970) and the numberof adultsforaging at any one time increases.Fledglings and adultsleave the heronrybetween late Jun and mid-Jul(Pratt 1970); at the sametime numberson the lagoondropped. Only small numbersof herons breed close to Abbott's and Limantour (Pratt 1983), where numberswere slightlylower during the breedingseason (Fig. 10). Abbott's, the onlysite without a heronryon its shores,had greatestnumbers from mid-Aug to mid-Oct. This pattern is similarto that in fall on the Farallones(DeSante and Ainley1980), whichpresumably involves wandering juveniles. Great Blue Herons may also concentratemore in estuariesand lagoonsduring summerand fall as ephemeralfreshwater habitats dry up. They feed in the shallowwaters of estuaries, freshwaterponds, marshes, flooded fields, open streamedges, and tidal reefs. They alsofrequent fields to preyon rodents.

AmericanBittern (Botaurus lentiginosus) On Point Reyes,American Bitterns frequent freshwater marshes, ponds, or swales,and occasionallybrackish marshes. Their statusas a veryrare year-round residentwith a winterpeak (Fig. 12) reflectsthe limitedsuitable habitat in the study area. Between 1970 and 1988 the median number of bitterns recorded on the PointReyes CBC was 3 (range1-10). A declinein wintersightings after early Jan (Fig. 12) may have been causedby birdsdispersing over a wider area as winter rainscreated additional habitat. Late May to Augrecords presumably pertained to localbreeders or fledglingsand possibly non-breeding, oversummering individuals. The only confirmedevidence for localbreeding was two birdswith a few tuftsof down on their headsat a freshwaterpond at Abbott'sLagoon on 28 Jul 1981 (DS). Bitternsbegin nesting early enough in California(Bent 1926, Palmer1962) thatfledglings from outside the studyarea presumably could arrive here by early Jul, but data are lackingon the timingof arrival. Palmer(1962) notedthat fall migrationis in Sep and Oct and mostspring migration is from Mar to mid-Aprbut that thereis "considerablewandering from late summerto earlyfall." Numbers are greatest on the northern California coast from early Sep to mid-May (McCaskieet al. 1979) and on the southerncoast from late Sep to mid-Apr (Garrettand Dunn 1981).

161 CANADA

•0 CATTLEEGRET LESSERGOLOEN- 40 20 PLOVER

20 10 100 JJA S O• 0 0

201EURABIAN WIGEON 10

HARLEQUIN DU

16 10

GR.WHITE-FRONTED ß •J J II 47 120 GOOSE 0 j j A'S•O•N'D•J•F•M•A•M •

60 ' ' • 2011 2312WILSON'S PHALAROPE

• PARABITICJAEGER

60 COMMON TERN

Figure12. Occurrencesof somevery rare aquaticbirds by l O-dayperiods (see Methods)from all records,1954-1982. WATERBIRDS AT POINT REYES

GreatEgret (Casmerodius albus) A common summerresident and uncommonwinter resident(Fig. 10). The seasonalabundance pattern at Bolinas(Fig. 10) reflectedthe tendencyfor Great Egretsfrom a rookeryat AudubonCanyon Ranch on BolinasLagoon's east shore to forageon the lagoon. The mediannumber of adultGreat Egretsnesting at AudubonCanyon Ranchfrom 1967 to 1981 was 172 birds(range 130-296; Pratt 1983). GreatEgret numbers at Bolinasbuilt up slightlyin Feb but increased sharplyin Mar, whenbirds begin occupying the rookery(Pratt 1970). Egg laying usuallypeaks in earlyApr, and the last egretsbegin building nests by mid-Apr (Pratt 1972a,b, 1974). Numbersstabilize on the lagoonfrom late Mar to late May, then reacha peak from earlyJun to earlyAug as adultsfirst leave their youngunattended and lateras the firstyoung fledge (H. Prattpers. comm.). The steadydecline in numberson the lagoonin Aug (Fig. 10) coincidedwith a reduced numberof occupiednests (Pratt 1970) and was due to post-breedingdispersal of fledglingsand adultsfrom the area. Seasonaluse at Limantourwas generally similar to that at Bolinasbut not to that at Abbott's(Fig. 10). Limantourand Abbott's are equallyclose to two smallegret rookeries(Pratt 1983); however,Limantour is closerto the large Bolinasrookery, and birdsconsistently seen flying along the coastwest of Bolinasduring the breedingseason (DS) appearedto be movingback and forth between the Bolinas rookery and Limantour. At Abbott's, the small numberspresent from Aug to Dec (Fig. 10) followedpost-breeding departure from Bolinas,as do the six Farallonrecords (21 Sep to 8 Nov, DeSante and Ainley 1980). The paucityof sightingsat Abbott'sbetween Jan and Mar may indicate poor foragingconditions caused by risingwater levelsafter winter rains, and the paucityof sightingsthere from Apr throughJul correspondsto the occupationof rookerieselsewhere. The lowerwinter numbersat all sitesare due probablyto the migration of most of the population to wintering locationsas distant as Baja California or the west coastof mainlandMexico (Palmer 1962). Great Egretsappear to foragemore in estuariesthan do Great Blue Herons, but they alsofrequent freshwater ponds, marshes, streams, and, especiallyin the rainyseason, fields and pastures.In Jun 1984, up to 56 Great Egretsfed in tidal poolsof the rockyreef from DuxburyPoint to BolinasPoint (RMS). Huntersfor the feathertrade drasticallyreduced egret numbersin Californiain the 1880s and 1890s, but becauseof legislativeprotection the populationrecov- ered substantiallyfrom 1911 to 1943 (Grinnelland Miller 1944). Great Egrets reappearedin the San FranciscoBay area in 1924 (Stoner 1934) and the first Marin Co. sightingswere of sevenbirds at Bolinason 7 May 1929 (Stoner1934) and one at Drake'sEstero on 7 Jun 1931 (Stephens1931). Thesebirds may have been nestingat nearby rookeriesat the time (Pratt 1983). Great Egretsrepro- ducedpoorly in the late 1960s and early 1970s becauseof DDT-inducedeggshell thinning,but a decreasein egg lossduring incubation since then suggeststhat the egretsare recovering(Pratt 1974). SnowyEgret (Egretta thula) A fairlycommon year-round resident (Fig. 10). A largerookery on WestMarin Islandnear San Rafael, about 22.5 km from Bolinas,has been activesince at least 1952 (Ralphand Ralph 1958, Pratt 1983). Seasonaland/or dailymovements of birdsfrom this or other San FranciscoBay rookeriesmay greatlyinfluence counts at wetlandsin our studyarea. Numbersat Bolinas(Fig. 10) were generallylow duringthe late Apr to Jul breedingseason (Stone and Rigney1978) but increased in Aug when young and adultsdepart from breedingcolonies in San Francisco Bay. Small numbersof Snowy Egretswintered at Limantourfrom early Oct to mid-Mar and occurredirregularly at other times (Fig. 10). The few at Abbott's

163 WATERBIRDS AT POINT REYES from late Jul to mid-Dec(Fig. 10) may havebeen birds dispersing after breeding, or potentialwintering birds that left the lagoonafter foragingconditions changed becauseof winterrains. Recoveriesof birdsbanded in San FranciscoBay suggest that juvenileSnowy Egrets migrate south for long distancesto winter (as far as southern California and Mexico), while adultsmove short distancesor winter near breedingareas (Gill and Mewaldt1979). Snowy Egretsforage in shallowestuaries, freshwater ponds, and marshes. They were nearlyextirpated from Californiabetween 1880 and the early 1900s by the ravagesof plumehunters, but becauseof legislativeprotection they recovered from 1908 to 1943 (Grinnelland Miller 1944). LittleBlue Heron (Egrettacaerulea) A very rare spring visitantwith censusrecords of singleadults at Bolinas Lagoonfrom 26 May to 3 Jun 1975 (AB 29: 903, ABN) and from 11 to 24 May 1976 (AB 30: 883, ABN). The onlyother records for PointReyes were of one to two birdsat BolinasLagoon from 18 to 27 May 1984 (AB 38: 953, ABN) andan immatureat Abbott'sLagoon on 2 Oct 1977 (KY, RMS). Althoughquite rare in coastal northern California, Little Blue Herons have been recorded in all but two years since first discoveredin 1964 (Unitt 1977, ABN). There are three docu- mentedwinter recordsfor northernCalifornia, all of immatures(Jeter and Paxton 1964; AB 36:326 and 889, AB 41: 322). Otherwiseall northern California recordsfall between18 Apr and 12 Oct (ABN), exceptfor one on 26 Nov (AB 41: 137). Most are of adultsnear heron or egret rookeriesin the San Francisco Bay area (Unitt 1977, McCaskieet al. 1979, ABN), where they presumablyhave been breedingsince at least 1981 and apparentlyalso hybridizingwith Snowy Egrets(Morlan and Erickson1988, AB 42: 1336). The few immaturessighted in summermay be locallyproduced or perhapspost-breeding dispersants from the south. In coastalsouthern California most recordsare of northward-dispersing immaturesin fall, with someremaining to winter;fewer adults occur in springand earlysummer (Unitt 1977, Garrettand Dunn 1981). Some have nestedannually in the TijuanaRiver Valley since 1980 (P. Unitt pers. comm.). Cattle Egret(Bubuicus ibis) A very rare late fall to early winter dispersant.Our only censusrecords--two birds on 1 Dec 1977, one on 4 Dec 1978, three on 7 Nov 1979, and two on 7 Dec 1979--were all from pasturesbordering Pine Gulch Creek at BolinasLagoon. Highestnon-census counts were of 18 birdson 23 Nov 1977 flyingfrom Bolinas Lagoonnorth up the Olema Valley(LES, GWP, SJ), 19 birdsnear Olema Marsh on 17 Dec 1977 (ABN: BDP), and 19 birds on 1 Nov and 20 birds on 24 Nov 1984 at BolinasLagoon (DS, RMS). Between 1970 and 1988, Cattle Egrets were recordedon 15 of 19 Point ReyesCBCs; the medianfor the 15 yearswas 3 (range1-30). Most Marin Co. recordsextend from mid-Octto mid-Janand peak stronglyfrom early Nov to mid-Dec(Fig. 12). Thispeak coincides with the peakin Washingtonand BritishColumbia (Roberson 1980) but is laterthan that in coastal southernCalifornia, where birdsare presentyear roundwith the largestnumbers occurringfrom late Sep throughearly Nov (Garrettand Dunn 1981). SinceCattle Egretsbreed in Californiafrom at leastApr to Aug(Cogswell 1977, AB 32: 1204) and young fledgeafter mid-May (AB 24: 716), one might expect initial post- breedingdispersal as early as Jun or Jul. However,noticeable northward movement on the WestCoast averages much later and correspondswell with the beginning of winter rains, which may influencefood availability.The importanceof rainfallto the seasonalcycle of Cattle Egretsis evidencedby rainfalltriggering breedingin South America (Lowe-McConnell1967) and the post-breedingdis-

164 W^TERBIRD$ AT POINT REYES persalof birdsin South Africa to areasof greaterrainfall (Siegfried 1970). By Feb, mostCattle Egrets have moved south of northernCalifornia. The mid-Aprto earlyJun records(Fig. 12) likelyrepresent northward spring dispersants. At that season birds have also been found in the eastern United States far north of known breedingareas (Palmer 1962). Cattle Egrets appear to have spread naturallyfrom the Old World to the Western Hemisphere,occurring in South America in 1877 and in Floridaby at least 1942 (Crosby 1972). They now have expanded over much of North America. The first recordfor Point Reyes--of one bird at Olema Marsh on 27 Dec 1970--coincided with the first widespreadinflux into northern California (AFN 24: 534) and followedthe first sightingin Californiain 1964 (McCaskie 1965). Nestingwas firstobserved in southernCalifornia in 1970 (AFN 24: 716) and in northernCalifornia in 1978 (AB 32: 1204). Despitea continuingpopula- tion increasein northernCalifornia as a whole, annualnumbers at Point Reyes haveremained relatively stable in the 1980s (PointReyes CBC, ABN). Siegfried(1978) describedCattle Egret habitatas the moist ecotonebetween aquaticand dry uplandareas. Locally,Cattle Egretsforage in moistshort-grass pastures,usually around dairy cattle, and muchless frequently in brackishmarshes.

Green-backedHeron (Butorides$triatus) A very rare fall and springvisitant with the only censusrecords being of single birdsat Abbott'son 25 and 31 Aug 1966, at Bolinason 11 Oct 1976, and at Limantouron 28 Apr 1970. This rarity reflectsthe limitedfreshwater habitat in the study area and the species' overall rarity in Marin Co. (Shuford 1982). Between1970 and 1988, Green-backedHerons were recordedon only 4 of 19 Point Reyes CBCs, with a high count of three. Green-backedHerons occur uncommonlyin northernCalifornia from early Apr to mid-Octand rarelyand locallyduring the remainderof the year(McCaskie et al. 1979); the averagespring arrival date in Sonoma Co. is 14 Apr (G. L. Bolanderand Parmeter 1978). A noticeable increase in numbers in the southern California deserts from late Mar throughearly May and from early Aug throughmid-Oct indicatesthe timing of migration(Garrett and Dunn 1981). Green-backedHerons frequentthe borders of streams,ponds, freshwater marshes, and, muchless commonly, brackish marshes.

Black-crownedNight-Heron (Nycticorax nycticorax) A rare summerresident and fairlycommon winter resident (Fig. 10). Bolinas wasthe onlystudy site on Point Reyeswith substantialnumbers of night-herons. Otherscattered census records, mostly from Abbott's, generally fit theBolinas pattern. Seasonaluse patterns at Bolinasprobably reflected movements to andfrom the breedingcolony at WestMarin Island, Marin Co. (Ralphand Ralph1958, Pratt 1983), or othermore distant San FranciscoBay colonies.Migration is limited in California,and build-upsand declinesat Bolinaswere the inverseof those at coastalnorthern California rookeries (Ives 1972, Stoneand Righey 1978). It is alsopossible that the increasein winternumbers at Bolinasinvolves migrant birds fromthe interior.Although band recoveries suggest that SanFrancisco Bay breedersare essentiallynon-migratory (Gill and Mewaldt 1979), at leasta few cen- tralCalifornia breeders travel to southernCalifornia and Mexico (Gill and Mewaldt 1979, Grinnelland Miller 1944). Black-crownedNight-Herons roost communally in the daytimeat traditionalsites near estuaries, ponds, and marshes where they feedmostly at night.

165 WATERBIRDS AT POINT REYES

White Ibis (Eudocimus aibus) A very rare springand summervisitant. An adulton BolinasLagoon from 14 to 19 May 1971 (AB 25: 794) and on a 23 Jun 1971 censusrepresents the only Point Reyesrecord. Apparentlythe samebird was presentin San Rafael,Marin Co., from 27 Jun to 9 Sep 1971 (AB 25: 901, AB 26: 113). This is the only northern California record, but the AOU (1983) and the CBRC (Morlan 1985) have concludedit was of an escapedcaptive. Others,however, favor a wild origin (AB 25: 794, McCaskieet al. 1979, Roberson1980). Jon Winter, in a report on file with the CaliforniaBird RecordsCommittee, summarized White Ibis sightings from AmericanBirds for the rest of the countryfor the springand summerof 1971. He found that an unprecedentednorthward surge of severalspecies of ciconiiforms,including the White Ibis, was attributedto droughtconditions in the southeastand southwest. This pattern, the lack of any escapeesreported from northern California,the bird'swariness, and the known tendencyof ciconiiforms to wanderto the north,all arguefor a naturalorigin of thisindividual.

TundraSwan (Cygnuscolumbianus) A very rare wintervisitant with a total of 63 birdson six censusesfrom 16 Nov to 9 Jan. Non-censusrecords extend the continuousdate span to 7 Apr (ABN, Fig. 12); an outlyingrecord of a bird at BolinasLagoon for one week in "late May" 1983 (fide RMS) was exceptional. On the northern Californiacoast most Tundra Swansoccur from mid-Nov to mid-Mar. Extreme datesare 1 Sep and 22 May, but recordsbefore late Oct or after earlyApr are exceptional(ABN). Our high censuscount was 27 birds at Limantouron 8 Dec 1980, and the high countfrom the studyarea was 125 birdsat BolinasLagoon on 13 and 14 Dec 1967 (AFN 22: 473, ABN). Most sightingsin the studyarea have been of transientflocks; however, up to 20 birdshave winteredirregularly since 1979 in a pastureat the south end of TomalesBay (ABN). From 1970 to 1988 Tundra Swanswere recordedon 14 of 19 Point ReyesCBCs; the mediannumber for the 14 yearswas 6 (range1-90). Despitesome recovery, numbers in Californiahave been greatlyreduced over former times (Grinnelland Miller 1944), even on the coastwhere they have alwaysbeen scarce(Willett 1933, Garrettand Dunn 1981). A bird thoughtto be a Bewick'sSwan (C. c. bewickii)was observedat Bolinas Lagoonon 12 and 13 Dec 1982 (AB 37: 333). This is the only coastalrecord of thisAsiatic subspecies which has been casualin Californiain the wintersince first recordedin Jan 1975 (AB 29: 736). Locally, winteringTundra Swans have been found on freshwaterponds and wet pastures,but mosthave been seen in flightor for shortperiods on marginsof estuariesor lagoons. Greater White-frontedGoose (Anser aibifrons) A veryrare fall andwinter visitant with 87 birdson eightcensuses from 15 Sep to 21 Jan; additionalPoint Reyes recordsfollow a similarpattern (Fig. 12) and extendfrom 3 Sep to 18 Apr (ABN, PRBO). Extremedates for coastalnorthern Californiaare 3 Sep and 31 May (ABN, Yocumand Harris 1975), exceptfor a 10 Jul 1988 recordon San FranciscoBay (AB 42: 1336). Most recordsextend from late Sep to early Mar, and ones in early Sep or May are exceptional. Our high censuscount was of 36 birdsat Bolinason 14 Dec 1973, and the high count for the studyarea was of 250 at BolinasLagoon on 25 Jan 1971 (AB 25: 621). White-frontedGeese have been recordedon only 7 of 19 Point ReyesCBCs from 1970 to 1988; the median numberfor the 7 yearswas 13 (range 1-30). Most Point Reyesrecords are of transientflocks, but occasionallya few birdswinter on

166 WATERBIRDS AT POINT REYES pasturesor grass-borderedfreshwater ponds. Historically,numbers in California have declinedgreatly both overall (Grinnelland Miller 1944) and on the coast, especiallyin southernCalifornia (Willett 1933). Snow Goose (Chen caerulescens) A very rare winter visitantwith 15 birdson nine censusesfrom 25 Nov to 10 Feb; additionalPoint Reyesrecords extend from 3 Oct to 14 Mar (Fig. 12, ABN). Coastalnorthern California records extend from 25 Sep to 23 May, except for three Jul-Aug records. Most birdsoccur from mid-Octto early Mar, and records beforeOct and after earlyApr are exceptional(ABN). Snow Geesewere recorded on 8 of 19 Point ReyesCBCs from 1970 to 1988; the mediannumber for the 8 yearswas 3 (range 1-32). The high non-censuscount was of 120 birdsflying over BolinasLagoon on 16 Nov 1980 (DS). Snow Geese on Point Reyeshave been observedin pastures,at grass-borderedponds, and around lagoon and estuarymargins. Historically,numbers of Snow Geesehave declinedgreatly in Californiaboth overall(Grinnell and Miller 1944) and on the coast,especially in southernCalifornia (Willett 1933). Ross' Goose (Chen rossii) A very rare visitantwith a singlecensus record of one bird at Abbott'son 13 May 1976. There are sevenadditional Point Reyesrecords of one to four birds lingeringfor a few daysbetween 30 Nov to 10 Feb (ABN) near freshwaterinflows to estuariesor lagoons,at sewageponds, and in agriculturalfields. Additionally, there are recordsof migrantsover the oceanof two birdsat the CordellBanks on 11 Oct 1986 (ABN: SFB) and of 11 birds 8 km northwestof TomalesPoint on 1 Nov 1986 (AB 41: 137). Coastalnorthern California records extend from 24 Sep to 16 Jun, with perhapsone bird oversummering;most records are from mid-Nov to late Mar (ABN). Althoughmuch reducedfrom former times (Grinnelland Miller 1944), the populationhas increased substantially since the 1950s (Bellrose1980). Numbersremain reducedon the southernCalifornia coast (Willett 1933, Garrett and Dunn 1981), but Ross'Geese were apparentlynever regular on the northern coast(Grinnell and Wythe 1927). A slightincrease in sightingsalong the northern Californiacoast in recentyears (ABN) is justas likelya resultof increasedobserver coverageand awarenessas it is an indicationof populationtrends. EmperorGoose (Chen canagica) A very rare winter visitantwith Limantour censusrecords of one on 27 Dec 1967 (also seen from 28 to 31 Dec, AFN 22: 473; CBRC) and two on 26 Dec 1968 and 7 Jan 1969 (one to two from 12 Dec 1968 to 9 Jan 1969, AFN 23: 515, PRBO). Detailsof these records,as well as those for non-censusrecords of one bird at TomalesBay on 18 Dec 1948 (AFN 3: 183) and of threebirds flying south off Limantouron 7 Dec 1966 (AFN 21: 453), have not been submittedto the CBRC. The three PointReyes (all Limantour) records accepted by the CBRC are of one bird on 13 Dec 1928 (Orr 1944), three that winteredfrom 28 Dec 1977 to 4 Feb 1978 and seen againfrom 9 to 22 Apr 1978, and anotherbird that joinedthe latterthree on 22 Apr (AB 32: 395, AB 32: 1050, ABN). The EmperorGoose is casualin California. The acceptedPoint Reyesrecords are among48 (24 coastal)for the statespanning 8 Oct to 26 Apr, 1884 to 1988; mostbirds do not arrivebefore Nov or linger past Feb (CBRC). The unsubmitted recordsabove are amonga backlogof 39 suchrecords; as thisgoose is so distinc- tive, most of theseare probablyvalid. Most of the Point Reyesrecords since the 1960s have been in flight years when birds were also seen at other coastal Californialocalities (AB 32: 395, AB 32: 1050, Roberson1980, Garrett and 167 WATERBIRDS AT POINT REYES

Dunn 1981), though the strong philopatric tendenciesof geese in general (Johnsgard1978) suggestthat the same individualsmay have returned to Limantour from 1966 to 1969.

BlackBrant (Branta bernicla nigricans) A rare summervisitant, an uncommonfall transientand winter resident,and a very commonspring transient (Fig. 13). On the surveyedweftands, Black Brant occurredregularly only at Limantour,which is contiguouswith Drake's Estero,a majorstaging area for the species.More than 50 Brantwere recordedat Bolinas (Fig. 13) only in spring 1973; one to three Brant were recordedon only seven censusesat Abbott's, with the exception of 39 on a 14 Nov 1981 census. Althoughrarely 100 to 200 birdshave been seen at Limantourin mid-Jun,later in the summerit is unusualto see as many as 10 to 20 birds;a non-censuscount of 131 birdsat "PointReyes" on 29 Aug 1968 (AFN 23: 100) was exceptional.In fall Black Brant migrate along the California coast primarilywell "offshore,"so southboundmigrants are only occasionallysighted from coastalpromontories (Garrettand Dunn 1981, ABN, authors'pers. obs.; however,compare Roberson 1985). The occasionalearly fall arrivalsin the Point Reyesarea from 29 Sep to mid-Oct(Moffitt 1941, ABN) may representmigrants headed farther south (Moffitt 1941, ABN). Fall migrationbegins in earnestin early Nov and continuesthrough earlyto mid-Dec(Moffitt 1932). Localwintering birds usually return to the Point Reyesarea about10-20 Nov (Moffitt1941, ABN). Only smallnumbers paused on the estuariesduring fall (Fig. 13), and currenfiynumbers remain low through the winter (seebelow). Largenumbers of springmigrants can be seenregularly from shoreduring the strongnorthwesterly winds characteristic of spring. Duringoffshore or slackwinds they occurwidely over inshore,offshore, and oceanicwaters. Black Brant were seen at least 190 km off central California in Apr 1987 (D. G. Ainley pers. comm.). On Point Reyesspring migrants are most visiblefrom the beach at Limantour. At this locationmany birds veer into Drake'sEstero to rest or feed or continuenorthwest over Drake's, by-passingthe Point Reyes headlands(DS). Drake'sEstero and TomalesBay are the main springstaging areas at Point Reyes (Table 2). Our censusesand those of the California Deptartment of Fish and Game do not supportthe report by Briggset al. (1987) that BolinasLagoon is an importantstaging area, thoughhundreds of birdssometimes concentrate nearby at DuxburyReef (RMS). AlthoughMoffitt (1932) formerlycounted thousands of wintering Black Brant in TomalesBay on 10 Feb censuses(Table 2), he detected spring migrantsas early as 11 Feb in some years. A flock of 2000 birds on Tomales Bay on 3 Feb 1988 (ABN: RS, DWm) probably representedearly migrantsas wintering numbersthere now averageabout 200 birds (Table 2). During our study,numbers on the estuariesincreased in late Feb, peakedfrom mid-Marto early May (Fig. 13), and declinedto summerlows by mid-Jun(Fig. 13). The low numbersat Limantourin late Mar (Fig. 13) reflectedthe high between- year and within-seasonvariation, as pulsesof migrantson estuariesmay go unde- tectedat 10-daycensus intervals (cf. Bayer 1983). Datesof peakspring migration over the inshorezone in centralCalifornia range from 30 Mar to 20 Apr (ABN: BSa et al.). Decreasesin numbersof Black Brant winteringin Californiawere evidentby the early 1900s, especially in southern California (Grinnell et al. 1918). HistoricallyTomales Bay, Drake'sEstero, and BodegaHarbor supportedlarge winteringpopulations, but sincethe 1950s numbersthere have declinedsubstan- tially(Table 2). The localwinter decline was part of a largertrend in whichthe bulk of the Californiawintering population shifted to Mexico (Bellrose1980). The

168 WATERBIRDS AT POINT REYES

average number of migrantsin Apr in Drake's Estero, TomalesBay, Bolinas Lagoon,and BodegaHarbor decreasedfrom 8000 birdsbetween 1961 and 1965 to 3000 between 1966 and 1970 (Calif. Dept. Fish and Game unpubl. data). Depletionof estuarineeelgrass (Zostera marina), the Brant'smain food source, and human disturbanceare thought to be the key factors responsiblefor the Brant's decline here (Moffitt and Cottam 1941, Cottam et al. 1944, Einarson 1965). Canada Goose (Branta canadensis) A very rare winter visitantwith a minimumof 116 birdson 39 censusesfrom 19 Sep to 1 May; most birdsare transientsbut a few winter. The highestcensus countwas of 33 flyingbirds at Limantouron 26 Jan 1974, and the highestnon- censuscount was of 170 over Palomarinon 24 Dec 1984 (PRBO). Most Canada Geesewere foundon Point Reyesfrom Sep to Apr (Fig. 12). The infrequentand abbreviatedoccurrence of the birdsat estuariesreflects the species'preference for freshwaterhabitats and adjoininggrassy fields, which are scarceon Point Reyes. From 1970 to 1988 the mediannumber of CanadaGeese on the Point Reyes CBC was 41 (range0-384); most of thesebirds were at freshwaterhabitat inland. In coastalCalifornia, Canada Geese are primarilywinter residentsor transients.A smallbreeding population, perhaps of B.c. moffitti, has been establishedin the San FranciscoBay area at least since 1959 (Lidickerand McCollum 1979, ABN) and perhapsas early as 1932 (Moffitt 1939, Sibley1952), and it is stillincreasing (ABN). These breedersmay have originatedfrom a recentsemi-captive flock of moffitti at Lake Merritt, Oakland (AFN 10: 276, AB 27: 913), or from birdsbred

Table 2 Numbers of Black Brant at Coastal Estuaries in Winter ø

Drake's and Limantour Years Tomales Bay esteros Bodega Harbor

1931-1942 b 5620 _. 854 2657 _+611 ½ 1425_+ 325 (n = 12) (n = 9) (n = 11) 1952 d 7900 2170 e 235f 1956-1968g 1330 + 264 (n = 13) 1966-1969 h _ 242 _+226 -- 1961-1971 • 118+ 110 338 _+148 0 (n = 9) (n = 7) (n = 9) 1970-1988J 207 _ 44 (Tomales, Drake's, and -- (n = 19) Limantour combined)

Countsfor mid-Decemberto mid-Februaryreported as the mean _ 1 standarderror; n = sample size. Moffitt(1943); counts made i0 Februaryeach year. Countsmade in Drake'severy year, in Limantouronly in someyears. d Leopoldand Smith (1953); counts made 6-13 January1952. Unclearif Limantourcounted this year. BodegaHarbor has had only occasional wintering Brant since 1953 (B.D. Parmeter unpubl. data). TomalesBay ChristmasBird Count (CBC), late Decemberto earlyJanuary each year. Drake'sBay CBC, late December each year. CaliforniaDepartment of Fishand Game unpublished data from January censuses each year. PointReyes Peninsula CBC, mid to lateDecember each year. 169 WATERBIRDS AT POINT REYES

1•7

IJunlJul I,a•g I $epI (•½•I 1,4o¾I Dec I Jon I FebI MotI •pr I/v• I

400 BL•K BRaT (L) • 800 0 11 ' i I JunI Ju I IAugl$eplOct I•v I•ec I JonIFeb I•rlApr I •1 •00

200 2Ol 10 • M•LARD(B) IJunlJul IAugI $ep IOct I NovI Dec I Jan I Feb I Mar I Aix'l MayI

GREEN-WlNOED TEAL (A) tt

I JunI J u I I AugI SepIOct I NovIDec I JanI FebIMar I AprI MayI I JunI Ju I I AugI Sep I OctINov I DecI JanIFeb I MarI AprI Mayl 800•GREEN-W(HOED TEAL(B) 800[ MALLARD (L) lO0

200

0 I. .

I JunI J u I I AugI $epl OctI NovI DecI JoriI FebI MarI Apr I MayI

Figure13. Seasonalabundance of the BlackBrant, Green-winged Teal, and Mallardin wetlandsof PointReyes. See Figure 4 fordetails. 170 WATERBIRDS AT POINT REYES

in captivityin the Bay Area in the early 1900s from eggscollected at LakeTahoe (Grinnellet al. 1918). CanadaGeese found on the Point Reyesestuaries in mid- summer,e.g., up to 35 birdsat BolinasLagoon in Jun and Jul each year since 1984 (RMS, ABN), may representdispersants from the San FranciscoBay breedingpopulation. Wood Duck (Aix sponsa) A very rare visitantto surveyedwetlands with onlyone censusrecord on 8 Nov 1979 from the upper Glenbrookpond behind LimantourEstero. Small numbers of Wood Ducksreside year roundon Point Reyes,primarily in the Oiema Valley, where ducklingswere seen at Mill Pond on 5 May 1980 (DS) and at Five Brooks Pond from late May through Jul from 1987 to 1989 (ABN). On Point Reyes numbersincrease only slightlyin winter, in contrastto the state-widepattern of numbersincreasing 37-fold in winter becauseof an influx of about 90% of the PacificFlyway population (Naylor 1960). From 1970 to 1988 Wood Duckswere recordedon only 12 of 19 Point ReyesCBCs; the mediannumber for the 12 yearswas 7 (range 2-78). A high winter count was of 55 birdsat Point Reyes Station on 23 Mar 1988 (ABN: RS). Becauseof the small numbersinvolved and the species' retiring habits, the timing of the local winter increaseis unclear. However,a bird at a ranchpond in open grasslandon outer Point Reyeson 5 Sep 1974 (ABN: WMP) was either a post-breeding wanderer or a fall migrant. SouthernCalifornia records, away from areaswith summerpopulations, reveal a winter build-up primarily from mid-Sep to mid-Apr (Garrett and Dunn 1981). Wood Ducksdeclined markedly in Californiaprior to 1915 and were considered extirpatedin the San FranciscoBay area (Grinnelland Wythe 1927, Grinnelland Miller 1944). Despite subsequentincreases, historical levels have not yet been reached(Naylor 1960, ABN). Wood Ducks prefer bodiesof slow-movingfresh water with overhangingvegetation along the marginsand extensivenearby forests on the floor of whichbirds forage for acorns. This habitatis sparsein our study area.

Green-wingedTeal (Anas crecca) A verycommon winter resident (Fig. 13). Numbersat Bolinasincreased slowly in fall but declinedmore rapidlyin spring,a patternnot evidentat Abbott'sand Limantour,where the speciesis scarcer(Fig. 13). Extremedates for Point Reyes were 8 Aug and 30 May (DS, ABN), exceptfor a male at the Bolinassewer ponds on 25 Jun and 30 Jul 1989 (DS). Winter numbers at Bolinas increasedfrom 1972-73 to 1976-77 but declinedin 1977-78 and subsequentlyremained low (Fig. 14). The upwardtrend correspondsto a continentalincrease of breedingand winteringnumbers (Bellrose 1980). However, numbersat Bolinaswere highest duringthe two wintersof the state-widedrought, 1975-76 and 1976-77, when birdsdisplaced from dried-upfreshwater habitats may have increasedthe usual numbersat estuaries. On Point ReyesGreen-winged Teal prefer the shallowest portionsof estuariesand freshwaterponds (especially early in the fall). Four or five individualsof the Eurasianrace of the Green-wingedTeal (A. c. crecca)have beenrecorded on PointReyes from 19 Nov to 4 Mar (AFN 21: 453, AB 29: 114, AB 31: 368, ABN, PRBO). First recordedin the state in 1962 (AFN 16: 364), this race is a very rare but annualwinter visitantin coastalCalifornia from 2 Oct to 5 May (ABN). Mallard(Anas platyrhynchos) Year-roundresident, varying from fairly commonin springand summer,to commonin fall, to fairly commonin winter (Fig. 13). Smallnumbers breed on

171 WATERBIRDS AT POINT REYES estuarineborders; larger numbers breed at freshwaterponds and marshes. Of any of the studysites, the upper portionsof Abbott'sLagoon, which are primarily freshwater, supportedthe largestnumber of breedingMallards. In the two estuaries Mallardswere most numerousin fall and early winter, but at Abbott'snum- berswere lowest in fall (Fig. 13). The fall to earlywinter peaks at Limantourand Bolinasmay havereflected the concentrationof birdson estuariesafter the dry season.The subsequentdecline may have represented dispersal to takeadvantage of freshwaterhabitat enhanced by winterrains and/or simultaneousor progressive dispersalto potentialbreeding sites. At Abbott's,low fall numbersreflected post- breedingdispersal and the subsequentincrease reflected the arrivalof wintering birds,some of whichperhaps remained to breed. AlthoughMallards prefer freshwaterponds, they alsouse tidal fiats (especially near freshwaterinflows), saltmarsh channels,flooded pastures, and ephemeralpools.

Northern Pintail (Anas acuta) A very rare summervisitant and an abundantwinter resident(Fig. I5). A recordof a pair at Home Bay on 17 June 1981 (DS) suggeststhe possibilityof occasionalbreeding on Point Reyes. Irregularnon-census records of up to 30 birds in mid-Jul(PRBO) perhapsrepresent post-breeding dispersants from San FranciscoBay (ABN), sincemigrants traditionally arrive in earlyAug (Fig. I5). At Bollhas"spring" departure usually was abrupt (a drop of 75 to 95% or 700 to 2500 birds)and variablefrom year to year,with the bulkof the populationleaving as early as Jan in 1978 (Fig. 16). Only in the droughtyears of 1975-76 and I976-77 did largenumbers of Pintailsremain into Mar. In all other yearsfrom 1972-73 to 1981-82, abruptdeparture from earlyJan to mid-Febcoincided with periodsof I6 cm or more of rain in a I0-day period,or 20 cm or more in a 20- day period. Heavyrainfall in late fall did not triggerdeparture of largenumbers of birds. At Abbott'sand Limantourmost Pintailsdeparted by late Jan or Feb in all years(Fig. I5). Protractedfan migration and abruptspring departure characterize the speciesthroughout its winter range (Bellrose1980). Althoughabrupt departure at Bolinasfollowed periods of heavywinter rains, it is unclearwhether Pintails werefleeing adverse conditions, such as the inundationof estuarinefeeding areas, or whetherthey were movingto newly floodedfreshwater areas inland. High winter numbersduring the 1975-76 and 1976-77 droughtyears (Fig. 14) may have been due to the lack of alternate freshwaterhabitats. On Point Reyes, Pintailsforage in shallowestuarine waters, on tidalfiats, and in freshwaterponds, and sometimesraft on deeperbays or eveninshore waters during migration. Blue-wingedTeal (Anas discors) A veryrare springtransient with eightrecords on sevencensuses from 13 Feb to 8 May. Althoughmost additional records were of springmigrants, some fell in everymonth of the year (Fig. 12, ABN, Point ReyesCBC). Three Blue-winged Teal have been recordedon only two of 19 Point ReyesCBCs from 1970 to 1988. Fall recordswere probablyunder-represented because of the difficultyof separatingthe Blue-wingedfrom the more numerousCinnamon Teal at that time of year;non-breeding-plumaged teal of thesespecies were generally assumed to be CinnamonTeal (however,see PhillipsI975). AlthoughBlue-wingeds are not known to breed on Point Reyes,at leastseven reports of from one to six birdsat scatteredsites between I8 May to 23 Jun, 1975 to 1988, suggestthey may breed here rarely. Coastalbreeding has been reportedfrom westernOregon (Wheeler 1965) and northern California(Yocum and Wooten 1956, ABN), but most records are basedon male Blue-wingedsassociating with unidentifiedfemales with broods, thusnot eliminatingthe possibilityof mixedBlue-winged/Cinnamon pairs. 172 WATERBIRDS AT POINT REYES

GREEN-WINGED TEAL

..e.''-.....-" ".e..e 50001AMERICAN COOT io ..e.'e" ß e..ß..,e' •oo•300• •oøøI ' ...... •o!GREATERYELLOWLEGS o.• '6•',• ',• ',•' •'•'•

MARBLED GODWIT :ß

: / BLACK-BELLIEDPLOYER ß .•'

....:',,., p...... • I ,ø=,r. / IOO IOOOI o 6 •19 •1 67 69 7l 7• 75 77 79 81

100E- KILLDEER 20001LEASTBANOPIPER 200•NORTNERN e"e"•'" '"'.. .e.. •000•' .•..ß...ß •..ß.- .e..ß ß.. f '"-i ß ß o i•-f ,,-•'"T , , .e'"e'..e, ; , , , T• , 67 69 71 7• 75 77 79 8• o• ,•,,/•, •,, 67 6• 71 7• 7• 77 7•

4000

DUNLIN 200•G•W• 3OO $ooo

2000

: 2000•AMERICANWIGEON iooo• ,ooo• •

67 69 71 7• 7

30C WILLET 'e.. / IOOICOMMON $"I•.PE '.• o ...... e,'"'".e..ß..t",*, ß....J..ß..4 , , , •0•BUFFLEHEAD ..•.?"•"• 67 69 71 73 75 77 79 8

20C•00 I001FORSTER'$ TERNß o ß , , ,

Figure14. Meannumbers of some wintering aquatic birds at LimantourEstero (solidline) and Bollhas Lagoon (dotted line) between !967-68 and !98!-82. Notegaps in the censusrecord for Limantour. WATERBIRDS AT POINT REYES

Wheeler (1965) and Connelly(1978) reportedthat from the 1930s to the 1960s the Blue-wingedTeal pioneered new breeding areas and increasedin numberon the PacificCoast, especially north of California. The speciestends to abandon drought-strickenareas to pioneer habitat far from the center of its

NORTHERN PiNTAiL (L) NORTHERNPINTAlL(A)•5[•o•

IJunlJulIAug I Sep I Oc• I Nov I Dec I Jan I Feb I Mar I•&pr I May •1

I JunI J u J I Augl$eplOct INo¾ IDec I Jon I Feb I Mar I Apr I A• m•

Figure15. Seasonalabundance of the Northern Pintailand CinnamonTeal in wetlandsof PointReyes. See Figure 4 for details. 174 WATERBIRDS AT POINT REYES breedingrange (Bellrose 1980), perhapsexplaining periodic influxes, both locally (23 birds in Marin Co., May-Jun 1980, DS) and throughoutcoastal northern California(e.g., AB 34: 926). Blue-wingedTeal inhabit shallow freshwater ponds and marshesand, lessfrequently, estuaries near freshwaterinflow or freshto brackish impoundments. Although overlapping broadly in habitat use with CinnamonTeal, Blue-wingedsare lesslikely to feed in water with emergentvegetation(Connelly and Ball 1984). CinnamonTeal (Anas cyanoptera) Although found year round, the Cinnamon Teal was principallya spring transientin the studyarea. Censusdata indicatethat it is uncommonin summer and fall, rare in winter,and commonin spring(Fig. 15). Springarrival began in Jan, with numberspeaking in Mar and decliningthrough Apr and May. A few remainedto breedon freshwaterponds, as reflectedby the Jun and Jul numbers at Abbott'sand Limantour(Fig. 15). Additionalbreeding sites in the studyarea include the Bolinas sewer ponds and other ponds at Limantour and Drake's

% 140

120 • :, ß o

/; ..'i 100 ; • :. - , ,/-• •, ,: _ ..

80- fi ;', ; /'.:'•.: •: 3: ; ß : ,,,:: , '.L / :' ! , , ß ,- ß I • :• I: • :0"? :' 60' - ,,.,-)• : 'z• //• : •• ,• :ß • : e:Y I : • • '

4• - ,:,. '• .. I' :: • '

0 •a - - ••_• I •u91Sep I Oct I •ov I DecI Jon Pebl•or•prl•l Figure 16, Numbers,expressed as a percentageof the winter mean, of the No•ern Pintail at Bolinas•goon during 1974-75 (brokenline), 1975-76 (do•ed line), and 1977-78 (solidl•e),

175 WATERBIRDS AT POINT REYES

esterosbut not tidal marshes,which are used in San FranciscoBay. Cinnamon Teal forage primarilyin shallowfresh water (cf. Blue-wingedTeal) but also use estuariesand brackishimpoundments.

Northern Shoveler(Anas clypeata) A commonwinter resident(Fig. 17). The earliestfall arrivaldate for Point Reyeswas 5 Aug 1962 (ABN: HLC). Numbersincreased from late Sep through early Dec (Fig. 17) at the two estuaries.Migration continues perhaps until mid- Dec (Palmer1976a). At Bolinasnumbers decreased steadily from Jan through Apr, in contrastto Limantourwhere birdsdeparted abruptly between late Jan and the end of Feb (Fig. 17). Shovelersused Abbott's to onlya limiteddegree, mosfiy from earlySep to mid-Jan. Irregularhigh counts at Limantourand Abbott's may have representedShovelers that had been flushedfrom nearbyponds and settled in our censusareas for briefperiods. It is unclearwhy Shovelers left Limantour by Feb becausebirds concentrated there on estuarinerather than on pond habitat, which was most subject to change during winter rains. Shoveler numbers increasedat Limantourduring the study(Fig. 14). A few May sightingsand a pair seen near Drake's Beach on 16 Jun 1981 (DS) suggestthat Shovelersmay nest occasionallyin the study area, as they do rarely around San FranciscoBay (Grinnelland Miller 1944, ABN). At Point Reyes,Shovelers feed in shallowfresh- waterponds, brackish ponds or impoundments,sewage ponds, and estuariesnear freshwaterinflow, especially in muddyareas such as the PineGulch Creek delta on BolinasLagoon.

Gadwall(Anas strepera) An extremelyrare summerand commonwinter resident (Fig. 17). Although Gadwallsbreed in moderatenumbers around San FranciscoBay (Gill 1977), they are irregularin Jun and Jul on Point Reyeswhere there is only one breeding record(AB 35: 974). Fall arrivalbegins in late Aug and probablycontinues until Dec. At Limantourfreshwater ponds hosted greater numbers than the estuary beforeNov, but later,after the commencementof winterrains, virtually all birds shiftedto the estuary(near freshwater inflow), perhaps because of risingpond levelsor depletionof food in the ponds(Fig. 18). Risingwater levelsor food depletionperhaps also explain the departureof Gadwallsfrom Abbott'sin early winter (Fig. 17). A preferencefor pondsmay explainwhy arrivalbegan two months earlier at Limantour and Abbott's than at Bolinas, where freshwater habitatis mostlylacking. At BolinasGadwalls concentrated at the mouthof Pine GulchCreek, the area of greatestfreshwater inflow. An upwardtrend in winter numbersat Bolinasand Limantour(Fig. 14) paralleleda "dramatic"post-1950s rise in the breedingand winteringpopulation (Johnsgard 1978, Bellrose1980) andan expansionof the species'breeding range (Palmer 1976a). Gadwallsoccur in freshwaterponds and the innermostreaches of estuarieswhere the substrateis softand muddy.

EurasianWigeon (Anas penelope) A very rare winter resident(Fig. 12). EurasianWigeons occurred most frequentlyat Bolinas,the wetland study site which also supported the largest numbersof AmericanWigeons. At Bolinas,Eurasian Wigeons wintered every year from 1975-76 to 1981-82. The total of 15 birds on 38 Bolinascensuses from 4 Nov to 1 Apr probablyoverestimates the total,because high counts there were of fourbirds on a 2 Feb1976 censusand five on 5 Feb1977 (ABN:RS) and many birdsprobably returned annually. However, single females were recorded on only 176 WATERBIRDS AT POINT REYES

2e5 2OO

NORTHERNSHOVELER(A)•t•o 100 GADWALL(L) IJunlJulIAugl SeplOct I• vI DecI Jan I Feb I Mar I Apr I •

268 324 I Juni j ui i Augi Sepl Oct i NayiDec i janl Febi Mari Ap;l• I

z4a NORTHERN 643

•ICAN WIGEON (A) SHOVELER(L) 4OO

k•E•l•k• WI•EO• (B)

I JunI J u I I AuglSeplOc• IN.viDeo I J•nlFeb I •r I APrI•1 •00

• 00•

Ijun Ij u iI Aug ISep IOct INav IDecI Jan I Feb IMar I Apr I • I IJunlJullAuglSep IOct INay IDec I Jan I Feb IMa• I Apr I•

1250 - : AMERICAN WIGEON (L) ,

7•

250

I JunI Ju I I AugI SepI OclI NavIDec I JanI FebI MarI AprI • I I JunIJ u I IA•I SeplOcll•v IDeclJanlFeb I MorI AprI •1

Figure17. Seasonalabundance of theNorthern Shoveler, Gadwall, and American Wigeonin wetlandsof PointReyes. See Figure 4 fordetails. WATERBIRDS AT POINT REYES

two censusesand a numberof otherswere probablyoverlooked. Sevenrecords on seven censuses from 27 Oct to 15 Mar at Limantour and Abbott's were all of transients.Eurasian Wigeons were reported on 14 of 19 PointReyes CBCs from 1970 to 1988 with a high countof 4. At Point Reyes,extreme dates of occurrence were 10 Sep and 30 Apr. Exceptfor one 8 Jul to 7 Aug 1979 recordat Palo Alto (Morlan and Erickson 1988), extreme dates for coastal northern California are 9 Sep and 15 May (ABN). An apparent increasein Eurasian recordsat Bolinasover the courseof the studymay have been a resultof high AmericanWigeon populations in lateryears (Fig. 14). EurasianWigeons appear to have habitat preferencesidentical to those of AmericanWigeons (see that species),with which they associate. Locationsof most frequentsightings of Eurasiansin the studyarea includethe Pine Gulch Creek mouth at BolinasLagoon, Bolinas sewer ponds, Walker Creek mouth on Tomales Bay, Muddy Hollow pond at Limantour, and the ponds at Abbott's Lagoon. AmericanWigeon (Anas americana) A very rare summer visitant and an abundant winter resident (Fig. 17). Summer censusrecords were of one at Limantouron 10 Jul 1975 (GWP) and one at Abbott'suntil 24 Jun 1980 (DS). Non-censussummer records were of one at a pond near Drake'sBay 6 Jul 1964 (ABN: GM) and one at HorseshoePond on 10 Jul 1982 (DS). Fall arrivalon Point Reyessometimes begins as early as 8 Aug (1987, DS), but typicallyit commencesin late Aug (Fig. 17). At Bolinas,numbers peakedfrom Nov to Feb and birdsdeparted from Mar to May (Fig. 17). Numbers declinedsharply (by 35 to 75% or 350 to 550 birds)at Bolinasbetween late Dec and mid-Feb in 1972-73, 1974-75, 1977-78, and 1981-82 when 20 cm or more of rain fell in a 10-to-20-dayperiod; numbers there remainedhigh untilMar in the dry years of 1975-76, 1976-77, 1978-79, and 1980-81 (Fig. 2). Anomalousyears were 1973-74 and 1979-80 when numbersremained high despitemore than 20 cm of rain in late Dec and early Jan. These data suggest that cumulativeand short-termrainfall may affectdeparture but that other factors may alsobe involved. At both Limantourand Abbott's,numbers typically declined markedlyby Jan or Feb and remainedlow until final departurein May (Figs.17 and 18). The earlydecline at the lattersites occurred at the sametime somebirds shiftedfrom freshwaterponds to the estuariesand water levelsin the pondsrose followingwinter rains (Fig. 18). Other birdsleft the area probablybecause the wetlandscould not supportas largea populationof wigeonswithout suitable pond habitat. Wigeonsat Bolinasdid not rely as heavilyon freshwaterponds but were the only dabblingducks there that grazedintensively in moistpastureland and salt marsh. AmericanWigeons prefer shallow water where aquaticvegetation is available and are most numerouson freshwaterponds and on estuariesin areas of freshwaterinflow. Wigeonsoften associatewith AmericanCoots, which they rob of vegetationobtained by diving. Canvasback(Aythya ualisineria) A very rare summervisitant and a commonwinter resident(Fig. 19). The only two mid-summercensus records were from Abbott's on 27 Aug 1973 (RMS, RPH) and 28 Jul 1981 (DS). In fall birdsarrived a few weeksearlier at Abbott's and Limantourthan at Bolinas(Fig. 19). The winterof 1975-76 producedan all- time high countof Canvasbacksat Abbott's(winter mean 610), probablybecause of the drought-relatedshortage of habitatelsewhere. Within the studyarea, freshwater pondssupport the highestCanvasback concentrations, followed by bays, estuaries,and lagoons.

178 WATERBIRDS AT POINT REYES

Redhead(A•/th•/a americana) A rare winterresident with censusrecords from 23 Sep to 5 Apr at Limantour and Abbott's (Fig. 19). Except for an unseasonalhigh count of 14 birds at Abbott'son 17 Jul 1988 (ABN: LJP), non-censusrecords extend from 11 Aug to 26 Apr (ABN, PRBO). Redheadsat Abbott's(Fig. 19) were either transientsor winteringbirds that shiftedhabitats, perhaps because of changingwater levels from winter rains or depletionof food. The mediannumber of Redheads,primarilyfrom a flock winteringnear Walker Creek'smouth on TomalesBay, was 295 (range 0-1006) on the Tomales Bay CBC from 1956 to 1968 and 298 (range1-784) on the Point ReyesCBC from 1970 to 1981. The TomalesBay flockwas not seenon the Point ReyesCBC from 1982 to 1988, when Redhead numbersranged from 0 to 15. Otherwise,high countsin the studyarea of fall transientson freshwaterponds have exceeded20 birdsonly four times,with a maximumof 43 birdsat Limantouron 10 Nov 1965 (TVV et al.). Away from TomalesBay, Redheadsare foundon Point Reyeson freshwaterponds. Redheadswere formerlyquite commonin Californiabut by the early 1900s had been greatly reducedin number at all seasons(Grinnell et al. 1918, Grinnell and Miller 1944). On the North American continent as a whole, the Redhead populationhas decreaseddrastically because of drainageof breedinghabitat (Cogswell1977) and overshooting(Palmer 1976b).

2S0

GADWALL200I RUDDY

I Jun I J u I IAugI SepI Oct INov I DecI Jan I Feb I Mar I Apr I MayI 0I I Jun I Ju • I AugI SepI Oct II%1ovI Dec I JanI Feb JA•tr I Apr I/• I

_--

1oo• AMERICAN COOT

4oe ,.•

ß 300

2oe

ß ß

...... •.._...•?":! I jun AMERI J u I I•u91 $epI Oct Ir*4ovIDe½ I Jan I Feb I MarI •p; I,'v•ay! oI JunI J u I IAugl Sep loot 11'4orIDec I Jan I FebIMor I AprI/•1 Figure18. Mean numbersof the Gadwall,American Wigeon, Ruddy Duck, and American Coot in Limantour Estero (solidline) and ponds associatedwith Limantour(dotted line) between 1967 and 1974.

179 WATERBIRDS AT POINT REYES

11oo

CANVASBACK (A)

IJunlJul I AugI $epI OctINov IDec I JanI FebI MarI AprI May!

40[RING-NECKED DUCK(L)I

I JunI Ju I I AuglSepl Oc{ INov IDec I JanI FebI MarIApr I MayI

IJunlJul IAu91$ep I Oc•INo¾ I DecI JoriI FebI MarI AprI May

2e0e i=704

1009

_ CANVASBACK(B) SCAUP SPP. (A)

IJunlJul IAugI $epI Oct INov IDec I JanI FebIMar I AprI MayI

I JunI Ju I IAugl$epl Oct INov I DecI JanIFeb IMar I AprI MaYI

IJunlJul I AugI SepI OctI NovI DecI JanI FebI MarI AprI MaYI

I JunI J u I I AugI SeplOct INov IDec I JanI FebI MarI AprI/vkzyl

IJunlJul I AugI $epI OctI NovI DecI JanI FebI MarI AprI MayI

REDHEAD (L) .,{1{ ,..... 4 f++f I JunI Ju I I AuglSeplOct INov IDec I Janl FebI MorI AprI MayI I JunI J u I I AugI SepI OctI NovIDec I JanI FebI MarI AprI/day I

Figure19. Seasonalabundance of somediving ducks in wetlandsof Point Reyes. See Figure4 for details. 180 WATERBIRDS AT POINT REYES

Ring-neckedDuck (Aythya collaris) A very rare summervisitant, an uncommonfall transient,and a rare winter residentat freshwaterponds at Limantour and Abbott's (Fig. 19). The only summerrecords are of a female on 16 Jul 1980 at Muddy Hollow Pond (AB 34: 926), two malesand a femalethere on 20 Jul 1981, and a femaleon 28 Jul 1981 at HorseshoePond (DS). Otherwise,extreme dates of occurrencein the study area are 5 Sep and 3 May (ABN). On PointReyes most birds occur from Oct to earlyDec (Fig. 19). Thispattern may have reflected passage of migrantsor a local shiftingof birdsto non-censusedponds as habitatsuitability changed during winter rains. A flock of 87 Ring-neckedDucks at Five BrooksPond on 21 Dec 1979 (JGE)was an unusualconcentration for the studyarea. The Mar and Apr records at Limantoursuggest a limitedspring passage (Fig. 19). Ring-neckedDucks show a strongpreference for shallowfreshwater lakes, ponds, and reservoirs.The only local records for estuarieswere of one bird on 7 Dec 1985 (DS), 26 on 27 Dec 1986 (RMS, DS), and one on 15 Nov 1988 (RMS, PA), all on BolinasLagoon near the mouth of Pine Gulch Creek.

TuftedDuck (Aythyafuligula) A very rare winter visitant with sightingsof two to three birds on seven censuses from 7 Oct to 3 Mar, 1979 to 1982, at Limantour and Abbott's. Becausebirds return in successiveyears and may move betweensites both in the sameand in successiveyears, it is difficultto assessthe exactnumber of individuals involved(Dunn 1988). The CBRC currentlyaccepts two recordsof the Tufted Duck for Point Reyes:(1) one male at Limantourfrom 7 Jan to 17 Apr 1978 that returned23 Nov 1978-10 Mar 1979, 29 Sep 1979-12 Jan 1980, and 3 Oct-27 Dec 1980; in 1981 it was first seen at the HorseshoePond, Drake's Beach, from 26 Oct to 14 Nov, then returned again to Limantour from 5 to 19 Dec; (2) a second male at Limantour from 9 Nov to 2 Dec 1980 that returned to the HorseshoePond on 8 Nov 1981 then again to Limantourfrom 5 Dec 1981 to 3 Jan 1982. A pair at Limantouron 7 Nov 1981 was rejectedby the CBRC. The Limantourbirds were seenmostly at Muddy Hollow Pond and occasionallyat the largerGlenbrook pond. A recordat Abbott'sof a male from 5 Feb to 3 Mar 1980 (felt to representthe secondmale that was seen the followingfall at Limantour) was acceptedby the CBRC (Dunn 1988). It is currentlybeing reviewedagain alongwith more recenfiysubmitted Abbott's records for 14 Jan 1981 and 7 Oct 1981-22 Feb 1982. A 7 Nov 1982 record for Abbott's and a 15 Feb 1987 recordfor TomalesBay have not been submittedto the CBRC. All the records for Abbott'smay be rejectedas representingpossible hybrids (D. Robersonin litt.). Tufted Ducks have been expandingtheir palearcticbreeding range (Palmer 1976b), and sightingsof vagrantsto North Americahave increasedsince the early 1970s (Bellrose1980, Roberson1980, ABN). The first California record was in the winter of 1948-49 (Orr 1950, 1962, Dunn 1988), and the specieshas been recordedannually in the state since 1968 (CBRC). Except for one of oversummering, the 40 currentlyaccepted records for California(mostly coastal slope) span29 Sep to 11 May; mostare for Nov-Mar (CBRC).

Scaupspp. (Aythyaspp.) Becausemany Greater Scaups(A. marila) and LesserScaups (A. affinis) were indistinguishableor• censuses,we presentdata for both speciescombined. Scaups were rare summervisitants and very commonwinter residents(Fig. 19). Careful non-censusidentifications revealed that the seasonalabundance pattern at Bolinas (Fig. 19) wasbased primarily on the GreaterScaup, which apparently arrives later 181 WATERBIRDS AT POINT REYES

and departs earlier from the wintering groundsthan does the Lesser Scaup (McCaskieet al. 1979, Bellrose1980). The scaupson fresh water at Abbott's Lagoonin 1975-76 were mostlyLessers (Fig. 20). Typically,the increasein numbersof both speciesin fall wasmore gradualthan the decreasein spring(Figs. 19 and 20). Greater Scaupsuse deep bays, estuaries,lagoons, and, to a limitedextent, freshwaterponds. Although Lessersoverlap with Greaterson saltwater,they occurmuch more frequenfiyon freshwaterponds and generallyprefer fresher and shallowerwaters than do Greaters(Palmer 1976b).

100 -

-- 50- EXCEPT 1975-76

I JunI J u I I AuglSep IOct INov IDec I JanI Febl MarI Apr I MayI

3000 -

-- 2500 - _ 1975-76

2000 -

-- 1500 -

- 1000

500 -

.... •'•un I Ju I I Au91Sep I Oct I Nov I Dec I Jon I Feb I Mot I Apr I

ß Fiõure 20. Numbersof scaupsat ^bbott's Laõoon in 1975-76 and all years except1975--76. See Figure4 for details.

182 WATERBIRDS AT POINT REYES

From carefulidentifications we can reportthe following: Greater Scaup. Although of irregular occurrence,a few oversummering Greater Scaupcan be foundalmost every year somewhereon Point Reyes. High summercensus counts were 9 and 12 birdsat Abbott'son 15 Jul and 4 Aug 1981 (DS), respectively.The winterbuild-up of Greatersbegan in late Sep or earlyOct, and most birds had departedby mid-May. A high winter number for the study area was 8000 on TomalesBay on 18 Jan 1987 duringa run of PacificHerring (ABN 41: 323). LesserScaup. Althoughthe onlysummer census records were of two to three birdsat Abbott'sthroughout the summerof I981, numberson additionalcounts there increasedsteadily from 10 to 50 birdsfrom 6 Jul to 12 Aug 1965 (PRBO). A flock of 40 at Abbott'son 21 Aug 1979, if not oversummering,was a month earlierthan the usualarrival date for centralCalifornia (AB 34: 195). Regardless, LesserScaups were not seen most summersin the Point Reyesarea, despitetheir breedingirregularly in the San FranciscoBay area (Grinnelland Miller 1944, AB 40: 1250, AB 42: 1336). At Abbott's,in most yearsLessers occurred primarily as fall transients(Fig. 20). An unusuallylarge concentrationof 2800 birdson the largeupper freshwaterarm on the 14 Jan 1976 census(Fig. 20) was composed perhapsof refugeesfrom freshwaterhabitat that had driedup becauseof drought. Within the studyarea LesserScaups were usuallypresent from late Sep to mid- May. King Eider ($ornateria spectabilis) A very rare fall visitantwith only one censusrecord of an immaturemale at Abbott'sLagoon from 13 to 28 Nov 1980 (AB 35: 220, Binford 1985). The only other acceptedrecord for Point Reyesis a specimenof a juvenilefemale col- lectedfrom amonga group of three eidersat the mouth of TomalesBay on 16 Dec 1933 (Moffitt 1940, Dunn 1988). Recordsof a dyingfemale at Bolinason 26 Oct 1973 and another dead female at Bolinason 2 Nov 1973 (AB 28: 100) have not been submittedto the CBRC. Individualsof this circumpolar,high-latitude speciesoccur only irregularlyas far southas California (Roberson1980, AOU 1983). The 23 acceptedrecords for California,1933 to 1986, are of single birdsspanning all monthsof the year (CBRC). Most birdsoccur from Nov to Mar on coastalbays, estuaries, lagoons, or inshorewaters. HarlequinDuck (Histrionicushistrion icus) A very rare winter visitantwith one censusrecord of a male at Drake's Estero on 2 May 1980. Midsummerstudy area recordsare of "flocks"in Jun 1880 at Point Reyes (Maillard 1904), a female at Stinson Beach on 10 Jul 1980 (ABN: COB), and a male at Bolinas on 25 Jun and 12 Aug 1988 (ABN: RD, DAH). Most localrecords fall betweenSep and Mar with a peak from late Nov to mid-Jan (Fig. 12). Winter numbershave decreasedat Point Reyes. In the TomalesBay area there were "hundreds"in the fall of 1913 (Grinnellet al. 1918), "flocks"on 22 Dec 1929 and 28 Nov 1936 (Grinnell and Miller 1944), at least 10 birds on 13 Dec 1955 (AFN 10: 277), and 16 on 25 Nov 1956 (AFN 11: 54). On TomalesBay CBCs from 1956 to 1961 the median numberof HarlequinDucks was 8 (range1-15), and from 1962 to 1968 it was 1.7 (range0-6). From 1970 to 1988 Harlequinswere recordedon only 8 of 19 Point ReyesCBCs (high count 2), althoughthis countexcludes the area aroundthe mouth of TomalesBay where numberswere seen in the past (ABN). The specieshas declinedmarkedly as a breederin California(Remsen 1978, McCaskieet al. 1979), but sightingsin the breedingseason in the Yosemiteregion have increasedin the last 10 years(Gaines 1988). The declinein winter numbersin the Point Reyesarea may be a reflection

183 WATERBIRDS AT POINT REYES

of the decreasedsize of the Californiabreeding population, although the sourceof winteringbirds is unknown. WinteringHarlequin Ducks are foundin the inshore zone in turbulentwaters along rocky coastlinesand in baysand estuaries,particularly larger ones.

Oldsquaw(C!angula byemalls) A very rare winter residentwith only 9 birdson 14 censusesfrom 15 Oct to 9 May. Most birds in the Point Reyesarea were presentfrom mid-Oct to mid-Apr (Fig. 12). The highestcensus count was two at Limantouron 14 Mar 1969, and the highestnon-census count was 15 off TomalesPoint on 14 Jan 1976 (GWP, DS, NS). From 1970 to 1988 Oldsquawswere recordedon 12 of 19 Point Reyes CBCs with countsranging from one to five birdsexcept for a high countof I3 in 1975. The onlyPoint Reyesrecords for mid-summerare of singlebirds at Bolinas Bay on 3 Jun 1968 (AFN 22: 644), TomalesBay on 28 Jun 1981 (AB 35: 974) and from 21 Jun to 8 Jul 1986 (AB 40: 1250), and Drake'sBay from 23 May to 10 Jul 1982 (ABN: JGE et al.) and from 5 May until at least 5 Jul 1988 (AB 42: 1336, ABN); a bird at Abbott'son 9 Sep 1984 may have summeredlocally also (AB 39: 97). Oldsquawsinhabit inshore waters, bays, estuaries, ar/d lagoons.

BlackScoter (Melanitta nigra) A very rare summer visitant and winter resident with about 61 birds on 53 censuses,mostly at Limantourfrom Nov to May (Fig. 21). All censusrecords of BlackScoters fell between14 Nov and 15 May exceptfor one at Abbott'son 27 May and 5 Jun 1980, one at Limantour on 7 Jul 1970, one there on 2 Aug 1971, and two there on 14 Sep 1969. The high censuscount was 18 birdsat Limantouron 28 Apr 1968. AlthoughBlack Scoterswere not recordedregularly on censusesuntil Nov, fall migrationappears to startby earlyto mid-Oct(ABN), or rarely by late Sep (e.g., AB 39: 97). BlackScoters are more numerousin deeper and largerbays such as TomalesBay, where the highestcount was 93 birdson 21 Dec 1985 (BB). The bulk of the Point Reyespopulation inhabits inshore waters and has a seasonaloccurrence pattern (Fig. 5) similarto that of estuarinebirds (Fig. 21). A high winter count in the inshorearea from Drake's Bay to Point ReyesLighthouse was 150 birdson 13 Jan 1981 (AB 35: 332), and a high spring count was 200 birds on 6 Apr 1971 (ABN: BMc); typicallyfewer than 100 birds occurthere (ABN, DS). Up to eight birdswere observedin Drake's Bay in early Jun 1976, but only one or two have been foundthere later in the summer(ABN). Another concentrationarea is the rockyshoreline from DillonBeach to EsteroSan Antonio, where 75 were countedon 18 Feb 1978 (DS). From 1970 to 1988, the mediannumber of BlackScoters on the Point ReyesCBC, whichdoes not include outerPoint Reyesor the mouthof TomalesBay, was 59 (range16-115). Limited numbers of Black Scoters migrate over inshore waters of central Californiain spring,primarily in Apr and May (ABN: BSa et al.). Black Scoters preferinshore waters near the mouthsof estuaries,along stretches of rockyshoreline, and insidelarger bays; smaller numbers frequent estuaries and lagoons.They appear to forage over coarsegravel, boulders, and rock substratein the intertidal zone (Vermeer and Bourne 1984).

Surf Scoter(Melanitta perspici!!ata) A fairly common summerresident and a very common winter resident(Fig. 21). The fall influx began in late Sep or early Oct and continuedinto Nov at Bolinasand Limantourand into Dec at Abbott's (Fig. 21). Winter numberswere erratic at Bolinas(Fig. 21) perhapsbecause of the frequentinterchange of birds

184 WATERBIRDS AT POINT REYES

WHITE-WINGED SCOTER (B)

174 16e

IJunlJul I AugI SepI Oct INovI DecI JanI FebI MarI AprI MayI

593 579640

I JunI Ju I I AuglSep I OctINov IDec I JanI FebI MarI AprI Mayl SURF SCOTER

(A) 153

SCOTER (L)

I JunI Ju I IAugI SepI OctINøv I DecI JanI FebI MarI APrI Mayl

SURF SCOTER (B) I Jun I J u I I AugI SeplOct INov IDec I JonlFeb IMor I A )r I MayI

.... IJ•nlJ•l I •u• I •ep I 0½t I1•o¾I D•½I J•n I •b I Mo•I •l•r I MayI I JunI Ju I IAugI SepI OctINov IDec I JanIFeb I MarI AprI •ay I

150•COMMON GOLDENEYE(B) I JunI J u I I AuglSep I Oct INovI DecI JanIFeb IMor I AprI MayI

156 WHITE-WINGED SCOTER (A) 0[...... , I JunI Ju II AuglSeplOct INov IDec I JonlFeblMorI AprI MayI

COMMON GOLDENEYE (L)

IJunlJul I AugI $epI Oct I No¾IDec I JanII=eb I MotI AprI MayI I JunI J u I I AugI $epI Oci'lNovIDec I JonI FebI/•or I AprI/v•yl

Figure21. Seasonalabundance of scotersand goldeneyesin wetlandsof Point Reyes. See Figure4 for details. 185 WATERBIRDS AT POINT REYES betweenestuarine and inshorewaters. Surf Scotersmaintained highest average numbersat Bolinasfrom earlyNov to mid-Mar. At Limantournumbers were relativelystable from Nov throughApr (Fig. 21). At Abbott'snumbers peaked in Nov and Dec and to a lesserextent in Apr and May; birdslingered through Jun (Fig. 21). Peak movementin fall over inshorewaters is duringthe firsttwo weeksof Nov (Ralph 1969). An estimated110,000 Surf Scotersoff Point ReyesBeach from 31 Oct to 25 Nov 1987 was an exceptionallylarge flockof stagingmigrants (AB 42: 129). Alongthe southshore of Point Reyes,Surf Scoterswere concentrated mosfiyin Drake'sBay (Fig. 7). In inshorewaters numbers rose from Oct through Dec, stayedat a plateauthrough May, then declinedto reachyearly lows in Sep (Fig.5). To the northin coolerwaters off Cape Mendocino,numbers rise in Aug and Sep, peak in Oct or Nov, and usuallydecline gradually through the winter (Briggset al. 1987). Springmigration in the wetlandsextended mainly from late Mar throughMay (Fig. 21), bracketingpeak migrationdates over inshorewaters off centralCalifornia, which range from 16 to 23 Apr (ABN: BSa et al.). Our summerinshore counts (Fig. 5) of 796 birds(1204 adjustedfor unidentifieds)from I to 4 Jul 1981, and 580 birds(904 adjusted)on 17 and 18 Aug 1981, dwarfed those on the estuaries(Figs. 7 and 21). Declining numbersthrough Jun at Abbott's(Fig. 21) and from Junto Sep in inshorewaters off southernPoint Reyes (Fig.5) suggestedeven more protracted movement after the mainspring passage. At Point Reyes, Surf Scotersinhabit inshorewaters, bays, estuaries,and, rarely, freshwaterponds. Large numbersconcentrate on TomalesBay, presum- ablyeating eggs of PacificHerring (Briggs et al. 1987). Estimatesfrom Tomales Bay of 11,000 Surf Scoterson 28 Feb 1987 (AB 41: 323) and 10,000 on 28 Oct 1988 (ABN: JW) fell, respectively,during and beforethe annualperiod of herring spawning,suggesting that TomalesBay servesas both a major migratory stagingarea and a concentrationarea duringtimes of seasonallyabundant food. Of the three scoters,the Surf foragesover the widestvariety of substrates,from fine sandto boulderand rock (Vetmeetand Bourne 1984). In the inshorezone off Californiathey generally prefer waters over sandy substrate lying in the leeof a promontory(Briggs et al. 1987).

White-wingedScoter (Melanitta fusca) An uncommonsummer resident and a commonwinter resident(Fig. 21). Fall migration,concentrated between mid-Oct and mid-Nov,may continueinto Dec (Fig.21, Bellrose1980, AB 34: 196). Influxesto the weftandsbegan in Oct (Fig. 21). At Limantournumbers reached highs in Nov and Dec and declinedabrupfiy to moderatenumbers in Jan. At Bolinasnumbers peaked in Nov and declined graduallythereafter. After the fall influxin Oct, numbersat Abbott'sremained relativelystable through the winter. Irregularincreases in numbersat all sitesin mid- winter may have reflectedmovement between inshore and estuarinewaters, and from late Mar to mid-May may have representedpulses of migrants. Wetland numbersdeclined through May to summerlows by early Jun at Limantourand Bolinasor by early Jul at Abbott's;Bolinas was the only site where Surf Scoters were irregularin summer. Numbersof White-wingedScoters on inshorewaters off Point Reyesincreased from Oct to Dec, maintaineda mid-winterplateau from Dec to Feb, and declined somewhatin Mar and Apr (Fig. 5). In springWhite-winged Scoters migrate over inshorewaters between late Mar and May (ABN), thoughon our monthlyinshore countswe detectedstaging migrants on inshorewaters only in May (Fig.5). Peak migrationdates over inshorewaters in centralCalifornia range from 1 to 23 Apr (ABN: BSa et al.). Summernumbers remained relatively high on inshorewaters 186 WATERBIRDS AT POINT REYES

(Fig. 5), in contrastto the pattern on the estuaries(Fig. 21). At Point Reyes, White-winged Scoters frequent bays, estuaries,inshore waters, lagoons, and, rarely, freshwaterponds. In the inshorezone off southernPoint Reyes,White- wingedsconcentrated in Drake'sBay (Fig. 7). The ratio of the numberon estuariesto the numberon inshorewaters was higherfor the White-wingedthan for the Surf Scorer(Fig. 7, Table 1). Elsewhere,White-winged Scoters feed in deeper water than do the other scoterspecies and forageover silt, mud, sand,and fine gravel(Vermeer and Bourne 1984). On inshorewaters along the Californiacoast, White-wingedand Surf scotersoccupy similar habitat (see account, Briggs et al. 1987).

Common Goldeneye(Bucephala clangula) A very rare summervisitant and a commonwinter resident(Fig. 21). Our only summercensus records at PointReyes were of two birdslingering until 25 Jun and one lingering until 28 Jul 1975 at Bolinas. The only non-censusrecords for summerwere of one bird on 2 Aug 1964 at Bolinas(ABN: TAC, ZCh), one bird on 18 Jul 1965 (RS) at Abbott's,and two birdsthere on 17 Jul 1988 (ABN: LJP). The earliestfall arrivalwas 3 Nov at Bolinas. Althoughnumbers at Bolinasbuilt up abruptlythrough Nov, peaked in Dec, and subsequentlydeclined steadily, at Abbott'sand Limantourboth the fall increaseand springdecline were gradual(Fig. 21). Most goldeneyesin the Point Reyesarea were found on estuaries,bays, and lagoons, with smaller numbers in the inshore zone and on freshwater ponds, impoundments,and sewageponds.

Barrow'sGoldeneye (Bucephala islandica) A very rare winter residentwith about eight individualson 18 censuses(17 at Bolinas, 1 at Limantour) from 9 Nov to 8 Mar. Non-censusrecords from Point Reyesextended from 31 Oct to 28 Apr (ABN) with most recordsbetween Nov and Jan at BolinasLagoon or Tomales Bay (Fig. 12). The earliestrecord for coastalnorthern Californiais 28 Oct (Grinnelland Miller 1944), except for the unprecedentedarrival of six birdsat FosterCity, San Mateo Co., on 26 Sep 1982 (ABN: DPM). Barrow'sGoldeneyes were reportedon 10 of 19 Point ReyesCBCs from 1970 to 1988; 12 birdsin 1978 was the only countover 3. Althoughthe specieshas alwaysbeen rare and local in the state in winter (Grinnelland Miller 1944), its extirpationas a breederfrom Colorado (Palmer 1976b) and California (Cogswell1977, Remsen1978) may have causedcoastal wintering populations to decline. However,as recentlyas 1987 winternumbers appeared to be rebounding in the San FranciscoBay area (J. Morlan pers. comm.), where most coastalbirds reside(Cogswell 1977, ABN). Barrow'sGoldeneyes use bays,estuaries, lagoons, freshwaterponds, and sewageponds.

Buffiehead(Bucephala albeola) A rare summerresident and a very commonwinter resident(Fig. 22). Up to sevenbirds oversummered at Abbott'sin four of five yearswith summercensuses, whereas none oversummeredat Limantour or Bolinas, despite longer census records. Numbersincreased abruptly from late Oct to late Nov, but thereafter occurrencepatterns at the variousweftands differed substantially. At Bolinasnum- bersremained relatively stable from Nov to Apr; at Limantournumbers declined slowlyfrom Dec throughMay; at Abbott'snumbers remained relatively stable from Nov to Feb, but increasedin Mar and Apr (Fig. 22). Thesepatterns suggest com- plex local movementsat leastone facet of which is the use by Buffleheadsof ephemeralponds createdby winter rains. An estimated4000 + Buffleheads

187 WATERBIRDS AT POINT REYES

BUFFLEHEAD (A)

RUDDY DUCK (A)

I Jun I J u I I Augl $epl 0½t INov IDec I Jon IFeb IMor I Ap• I Moyl

I JunI J u I I AugI Sepl Oct I NovI DecI JonI FebI MorI AprI MayI

i IJun IJ u I IAugI $epl Oct INov IDec I Janl FebIMar I AprI May 607 1245

RUDDY DUCK (B)

100

I JunI J u I I AugI $epl Oct INovIDe½ I JanIFeb IMar I AprI M•yI

I Jun I J u I I AugI $epl Oct INov IDe½I Jan I FebI •ml Apr I h•ayI [ ED-BRE&STEDMERGANiER(A) I Jun I ) u I I AugI $ep I Oct INo• IDec I )an I Feb I Mot I Apr iM•,l

lOO f

I JunI Ju I I Augl$eplOctlNov IDec I JanIFeb IMar I AprI Mayl I JunI Ju I I AuglSeplOct INov IDec I JanI FebI MarI AprI Mayl

Figure22. Seasonalabundance of the Bufflehead,Red-breasted Herganser, and RuddyDuck in wetlandsof PointReyes. See Figure4 for detai]s. WATERBIRDS AT POINT REYES were on TomalesBay on 18 Jan 1987 duringthe annualperiod of spawningfor PacificHerring (AB 41: 323). Overthe courseof the studythere was an increase in the populationwintering at Bolinas(Fig. 14). Regionaldeclines in the Westat leastthrough the mid-1960s(Grinnell and Miller 1944, Erskine1972) suggest Buffleheadsmay be lessabundant in Point Reyesestuaries than formerly. However,our censusdata and localCBCs since1956 indicatethat recentlynum- bers have been relativelystable. Buffieheadsfrequent estuaries, bays, lagoons, freshwaterponds, and sewageponds.

HoodedMerganser (Lophodytes cucullatus) A very rare winterresident with aboutseven individuals on 17 censusesfrom 8 Nov to 4 Mar. Non-censusrecords extend from 4 Oct to 3 May (ABN, PRBO) with most recordsfrom mid-Nov to late Mar (Fig. 12). Outsidethe area of breedingnear Lake Earl, Del Norte Co. (Yocumand Harris 1975), the earliest arrivalto coastalnorthern California is 3 Oct (ABN), the latestdeparture is 30 May (AB 42: 478), and the only recordof oversummeringis of a bird at Rodeo Lagoon,Marin Co., from 25 Jun to 25 Sep 1966 (AFN 20: 596, 21: 73). The highestcount at a singlesite on Point Reyeswas 30 birdsat Five BrooksPond on 14 Dec 1979 (AB 34: 303, ABN). The mediannumber of HoodedMergansers on the Point ReyesCBC from 1970 to 1988 was 5.6 (range 0-32). Hooded Mergansersoccur primarily on freshwaterponds and slow-movingstreams, especially those borderedwith vegetation,and occasionallyon estuariesat stream mouths.

CommonMerganser (Mergus merganser) A veryrare visitantwith onlyone censusrecord of threeindividuals at Abbott's Lagoonon 28 Aug 1981 (DS). Exceptfor CBC reportsthere are onlyfour non- censusrecords for Point Reyes:one bird at FiveBrooks Pond from 3 Dec 1976 to 8 Jan 1977 (DS et al.), one bird at SchoonerBay, Drake's Estero, on 12 Nov 1978 (DS, JW), five birdsat Abbott'son 13 Aug 1987 (ABN: ASH), and four birdsat Abbott'son 30 Aug 1988 (DS, SCc). CommonMergansers have been recordedon 16 of 19 Point ReyesCBCs from 1970 to 1988 with a median numberof 5 (range1-54) for those16 years. Many of the CBC recordspertain to birdssighted just east of the PointReyes Peninsula on streamsand reservoirs in watershedswhere the speciesbreeds (AB 35: 974). We suspectsome CBC reportsfrom Point Reyesproper are misidentifications.In coastalCalifornia the speciesoccurs primarily as a winter residentfrom Nov to Mar (McCaskieet al. 1979, ABN, Garrett and Dunn 1981), but it is rare from Marin Co. south (breedingsouth to Monterey Co.). In Californiathe speciesinhabits primarily freshwaterlakes, reservoirs,and rivers,but salt water only occasionallyduring migration or winter.

Red-breastedMerganser (Mergus serratot) A rare summerresident and a fairly commonwinter resident(Fig. 22). In summer,Red-breasted Mergansers were recordedmost frequentlyat Limantour (Fig. 22), where high censuscounts were 14 birdson 25 Jun and 16 Jul 1980. Seasonalchanges in abundanceat the wetlandsindicated that fall migration extendsfrom Oct throughDec and springmigration extends from Apr through May (Fig. 22). The smallnumbers of Red-breastedMergansers migrating over inshorewaters of the centralCalifornia coast peak in mid-Apr(ABN: BSa et al.). At Point ReyesRed-breasted Mergansers use bays, estuaries,lagoons, inshore waters,and, muchless frequenfiy, freshwater ponds. 189 WATERBIRDS AT POINT REYES

RuddyDuck (Oxyurajarnaicensis) A fairly commonsummer resident and an abundantwinter resident(Fig. 22). Most oversummeringbirds, on either salt or fresh water, are non-breeders. The only breedingrecords for Point Reyesare of a femalewith youngat a pond at Drake'sBeach visitors' center on 10 Jul 1982 (JGE)and at CypressGrove near Marshall,Tomales Bay, on 19 May 1989 (SK). In fall RuddyDucks arrived and reached peak numbersearlier at Abbott's Lagoon (Fig. 22) and on freshwater ponds (Fig. 18) than at Bolinasor the tidal areas of Limantour(Fig. 22). At Limantournumbers increased more rapidlyon the freshwaterponds than on the estero proper, but, with the advent of the rainy season,numbers on the ponds decreasedsteadily through winter, while numberson the esteroinitially increased and then remainedhigh until Feb (Fig. 18). An estimated3380 RuddyDucks were on TomalesBay on 28 Feb 1987 duringthe periodof spawningfor Pacific Herring (AB 421: 323). The springexodus from Mar to May (Fig. 22) encom- passedthe mid-Apr period of peak springmigration in North America (Bellrose 1980). Grinnell and Miller (1944) felt that numbers in California were much reduced from former times, a condition Palmer (1976b) attributed to market huntingin the late 1880s. Ruddiesin the PointReyes area are foundprimarily on TomalesBay, Abbott'sLagoon, and freshwaterponds, secondarily on the other estuaries,and onlyoccasionally on protectedinshore waters. BlackRail (Laterallusjarnaicensis) A very rare winter visitanton censuseswith only one recordof three birdsat BolinasLagoon on 14 Dec 1981. Non-censusrecords indicate the speciesis a year-roundresident and that birds dispersemore widely after breeding(ABN). Non-censusrecords at BolinasLagoon were of one bird callingalong the west shoreon 10 and 11 Mar 1979 (RS et al.), up to five individualsroosting together in the Pine GulchCreek delta during fall and winterextreme high tides from 1980 through1987 (ABN:RS et al.),one to twocalling birds at PineGulch from 2 Mar to 20 May 1987 (ABN: DDeS,DAH), and one to two callingon the eastshore on variousdates from 29 Mar to 11 Jul, 1983 to 1986 (ABN: CC et al.). A probable transientwas flushedfrom Salicornia marsh at Limantour on 27 Nov 1979 (AB 34: 196). AlthoughKehoe Marsh,3 km north of Abbott'sLagoon, supported up to fourwintering birds as late as 1975 (PointReyes CBC), none hasbeen reported there since 16 Dec 1978 (AB 33: 310). In Oct and Nov 1897, C. A. Allen col- lected22 Black Rails at the southend of TomalesBay (Brewster1907); others were collectedon TomalesBay throughat least 1940 (Manolis1978). Just how numerousthe BlackRail was there is suggestedby the 53 winter specimensfrom "Point Reyes"and TomalesBay at the AmericanMuseum of NaturalHistory, New York (fideSNGH). Eventhough subsequent conversion of much of the marshto pastures,starting in 1945 (D. Livingstonpers. comm.), has greatlyreduced the amountof tidalmarsh habitat, 17 BlackRails were capturedthere at high tidesby Great Egretsand Great Blue Herons over 11 days of observationfrom 21 Nov 1984 to 19 Jan 1985 (Evensand Page 1986), and recentsummer surveys yielded a highsummer count of sevencalling birds there on 16 May 1986 (JGE). Recentwork hasdocumented a substantialbreeding population of BlackRails in the tidal marshesof San Pabloand Suisunbays (Manolis 1978, Evenset al. 1989), thoughhistorically this populationappears to have declinedgreatly. The speciesis listedas threatenedin Californiaand is a candidatefor federallisting. On Point Reyes, nestingwas confirmedon TomalesBay near Invernessin the summerof 1966 (AFN 21: 73). Olema Marshrecords of a singlecalling bird from 7 Apr to 18 May 1975 (AB 29: 903), one callingon 5 Apr 1977 (Manolis1978), findup to four callingfrom 17 Jun to 30 Jul 1980 (JGE,DS), and the Bolinasand 190 WATERBIRDS AT POINT REYES

TomalesBay springand summerrecords listed above all suggestlocal breeding birds. An observationof two at Olema Marsh on 21 Sep 1930 (Stephensand Pringle1933) suggestsbirds also winter there. At all seasonsBlack Rails inhabit salt, brackish,and freshwatermarshes. In salt marshesthey are usuallyfound abovethe meanhigh tide line, and whilebreeding appear to favorareas that have a denseoverstow of Salicomiaor low-growingforms of Scirpus(Manolis 1978, PRBO unpubl.).

Clapper Rail (Rallus Iongirostris) A veryrare fall andearly winter visitant with onlyone censusrecord, of a single bird on Kent Island, Bolinas Lagoon, on 4 Dec 1981. Additional non-census recordsare of singlesat Bolinason 22 Dec 1967 (PL), 31 Dec 1978 (GWP), 15 Nov 1980 (AB 35: 221), and in spring 1972 (GWP); at Limantouron 31 Oct 1971 [Gull54(1): 3]; at TomalesBay in Oct 1965 (ABN: GB), from late Jul to 24 Sep 1969 (GB fide PL), and on 12 Sep 1982 (AB 37: 220); and at Schooner Bay, Drake's Estero, on 31 Dec 1966 (RS). Records of birds in northern California found out of habitat in fall extend from 3 Sep to 18 Nov (Evensand Page 1984). Most recordsin northern California away from known breeding areashave been duringfall and earlywinter and presumablyinvolve post-breeding dispersal.There is a pronouncedsouthward shift in winterof ClapperRails in the San FranciscoBay area (P. R. Kelly pers. comm.). It is possiblethat somewinter recordsinvolve birds dispersingfrom marshesinundated by exceptionallyhigh storm tides. Althoughthe CaliforniaClapper Rail (R. I. obsoletus)is still a locallyfairly numerousyear-round resident and breeder aroundSan FranciscoBay (Grinnell and Miller 1944, Gill 1979, Evensand Page 1984), it has declineddramatically sincethe late 19th centuryand is currentlyprotected as an endangeredspecies by state and federal governments. Initial reductionswere due to market hunting (Grinnellet al. 1918), but the lossof 60-95% of the bay'stidal marshes(Nichols and Wright 1971, Josselyn1983) has been the primary causeof decline and failureto return to historicallevels. The speciesstill facespressures from habitat fragmentationand introducedpredators. The declineof the San FranciscoBay populationhas probablyreduced the numberof fall and winter dispersantsto our studyarea. The historicalstatus of this speciesat TomalesBay, where marsh habitat has also been reduced(see Black Rail), is not clear. It was first recorded there on 22 Nov 1914 (T. I. Storer 1915, MVZ 24915), and singlebirds were collectedthere on 1 Nov 1936 and 11 Nov 1939 (CAS 66755, 66751). Since an adult female with an enlargedovary was also collectedthere on 21 Feb 1936 (MVZ 100396), and Clapper Railscan begin layingin early Mar (Evensand Page 1983), it is possiblethey once bred and were residentat TomalesBay. Intensive rail surveysfrom 1984 to 1986 at the southend of TomalesBay failedto reveal any birds(JGE, GWP). CaliforniaClapper Rails inhabit salt marshes,particularly thosewith extensivetidal channelsand sloughs.

Virginia Rail (Rallus limicola) A very rare year-roundresident with at least23 birdson 48 censuses.Its true status is masked by difficulty of detection--the Virginia Rail is probably an uncommonwinter residentand a rare summerresident. Away from the censused wetlands Virginia Rails occur more commonly on Point Reyes at scattered marshes. Overallthe localbreeding population is inflatedfrom Sep throughMar by winteringbirds that swell numbersin freshwaterand brackishmarshes and expandinto saltmarshes. The mediannumber on Point ReyesCBCs from 1970 to 1988 was 55 (range14-101). Censusesat Olema Marsh,the largestfresh- 191 WATERBIRDS AT POINT REYES

water marshon Point Reyes,yielded an averageof 20 birdsin winter 1985-86 and 11 pairsin summer1986 (Evensand Stallcup1986a,b). Breedinghas been confirmedon Point Reyesby the presenceof chicksat Olema Marsh on 1 May 1980 (DS) and on the west shoreof TomalesBay on 30 Apr 1967 (PL). Breeding habitatis probablyrestricted to swalesand freshwaterand brackishmarshes.

Sora (Porzana carolina) A very rare year-roundresident with about 11 birds on 14 censuses. Its true statusis maskedby difficultyof detection--theSora is probablyan uncommon winter residentand a very rare summerresident. All censusrecords fell between 27 Aug and 25 Apr exceptfor thoseof singlebirds at Bolinason 26 Jul 1973 and at Limantouron 10 Jul 1975. Away from the censusedwetlands Soras occur more commonlyat freshwatermarshes scattered around Point Reyes. Numbers swell in fall and winter and some birdsextend then into tidal marshes(JGE, GWP). The median number on Point Reyes CBCs from 1970 to 1988 was 8 (range 2-32). Althoughinfrequently reported on Point Reyesin the breedingseason, at Olema Marsh one to two pairs occur regularlyat that time versusone to six birds there in winter (Evensand Stallcup1986a,b). Two juvenilesat the Bolinassewer pondson 2 Aug 1983 were probablylocally produced (JGE). Like Virginia Rails, Sorasare probablyrestricted while breeding to swalesand freshwaterand brackish marshes.

CommonMoorhen (Gallinula chloropus) A very rare summervisitant and winter residentwith about sevenbirds on 11 censuses.All censusrecords were from freshwaterponds at Limantourbetween 6 Oct and 27 Dec, except for singleson 2 May 1980 and 2 Aug 1971. Point Reyes records,which peak from late Sep to mid-Nov (Fig. 12) are mostlyfrom Olema Marsh,Muddy Hollow Pond, and Five BrooksPond. Moorhenshave been foundon 11 of 19 PointReyes CBCs from 1970 to 1988 with the highestcount beingof three birds. Breedingon Point Reyesis irregularbut hasbeen confirmed by sightingsof smallyoung accompanied by adultsat OlemaMarsh on 31 Aug 1967 (AFN 22: 85) and at the Bolinassewer ponds on 12 Jul 1983 (AB 37: 1023). Breedingis alsosuggested by six or sevenimmature birds at a Limantour pond on 7 Oct 1964 (ABN: GM, KSc), one immature there on 16 Jun 1966 (PRBO), and a "pair" 3 milessouth of McClure'sBeach on 25 Jun 1972 (ABN: WBG). At Point Reyes,moorhens are restrictedto freshwatermarshes and ponds edgedwith emergentvegetation.

AmericanCoot (Fulicaamericana) A fairlycommon summer resident and an abundantwinter resident(Fig. 23). Coots breed on freshwaterponds at Limantour and Abbott's where a small increasein numbersduring summer (Fig. 23) was due to the fiedgingof young. Occasionalbirds at Bolinasin summerwere non-breedersor earlydispersing failed breedersfrom nearbyfreshwater habitat. Coot numberspeaked earlier and declinedmuch soonerin Limantourponds than on the esteroproper (Fig. 18), perhapsbecause some coots shifted to the estero when water levels in the ponds increased during the rainy season. However,there was a net exodusof cootsfrom Limantour(ponds and estuary combined)from Dec to Jan (Fig.23). At Abbott's,where water levels also typi- callyrise beginning in late fall, cootsalso peaked in fall and subsequentlydeclined. Funderburkand Springer(1989) noteda similarfall peak and earlywinter decline of cootnumbers at lakesEarl. and Talawa. At Bolinas,where freshwater habitat is 192 WATERBIRDS AT POINT REYES

IJunlJul I AugI SepI Oct I NovI DecI Jan I FebI MarI AprI MayI IjunlJullAuglSeplOcllNovlgeclJanlFeblMarlAprlMayl

600 • BLACKoBELLIED PLOVER (B) AMERICAN COOT (B)

400

300

-- I JunI j uI I AugI Sepl Oct I NovI Dec I Jan I FebI MarI AprI MayI

AMERICAN COOT (L)

BLACK-BELLIED PLOVER (L)

I JunI Ju I IAugI SepI OctI NovIDec I JanI FebI MarI AprI May• IJunlJulI AugI Sep I Oct I NovI Dec I JanI FebI MarI AprI MayI

Figure23. Seasonalabundance of the American Coot and Black-bellied Plover in wetlandsof PointReyes. See Figure 4 for details. 193 WATERBIRDS AT POINT REYES

lackingbut extensivefresh green grass is avilablein winterfor grazing,coots did not declinein Dec and Jan (Fig. 23). Winter numbersat Limantourdeclined after 1975-76 (Fig. 14). At Bolinas, winter numbersincreased from 1972-73 to 1975-76, then declinedsharply in 1976-77 and 1977-78 (Figs. 14 and 24). Coots also declinedfrom 1975 to 1976 on the Marin Co. (southern)CBC while increasingin 1975 and decreasing in 1976 on the Point ReyesCBC. The sharpdecline in peak numbersfrom the firstto secondyear of a majordrought may havereflected a concentrationof birds on the estuariesduring the firstwinter, as freshwaterhabitat dried up, followedby drought-inducedreproductive failure that causeda significantregional decline in numbers. Subsequently,coot numbersin our coastalstudy did not recoverto pre- drought levelsbut insteaddeclined further during the recent drought years of 1986-87 and 1987-88 (PRBOunpubl. data). In winter on Point Reyes,coots inhabitbays, lagoons,estuaries, freshwater marshes,and ponds,and graze on adjacentgrassy fields. They breed at freshwater pondsand marshesedged with denseemergent vegetation. Sandhill Crane (Grus canadensis) A very rare visitantwith a censusrecord of one bird at BolinasLagoon on 12 May 1975, apparentlythe same bird seen later that day on outer Point Reyes (BC). Other recentPoint Reyesrecords were of 13 flyingbirds at Bear Valleyon 16 Nov 1963 (ABN: CJR), two birdsat Palomafinon 24 May 1979 (KH, DDeS), one on Point Reyeson 27 Feb 1984 (AB 38: 353), one near Five Brooksfrom 29 Dec 1984 to 1 Jan 1985 (AB 39: 206), and singlebirds at Bolinasin "early fall" 1987 (NW, KH), on 11 Dec 1987 (PA et al.), and on 12 May 1989 (BHe). A bird on pasturesat the southend of TomalesBay from 16 Sep 1983 to 9 Mar 1984 (JGE et al.) is the only recentrecord of a crane winteringon the coastal slopeof northernCalifornia (ABN). SandhillCranes formerly wintered as closeas San Rafael and San Francisco,but numbersdeclined in Californiain the early 1900s (Grinnell and Miller 1944), and they are now extremely rare on the Californiacoast (McCaskie et al. 1979, Garrettand Dunn 1981, ABN). Sincethe 1950s SandhillCranes have visited the coastalslope of northernCalifornia irregularly, mostlybetween 6 Sep and 18 Jan (ABN). The only other coastalspring recordsbesides those for Point Reyes are of singlesat Aao Nuevo, San Mateo Co., on 9 May 1976 (AB 30: 884) and Oakland,Alameda Co., on 3 Apr 1988 (AB 42: 478). A SandhillCrane alsosummered in HumboldtCo. in 1974 (Yocum and Harris 1975).

Black-belliedPlover (Pluvialis squatarola) A fairly common summerresident and a very common winter resident(Fig. 23). Fall migrationextended from mid-Julthrough Oct (Fig. 23), possiblythrough Nov or later (Jurek 1973, DeSanteand Ainley 1980), and numberspeaked from earlyAug to late Oct (Fig.23, Jurek 1973). Juvenilesarrived at leastby Sep (DS); an early date for Oregon is 26 Aug (Paulson1983). Low numbersat Bolinasin Nov and Dec (Fig. 23) probablywere due to daily localmovements rather than a departureof migrants;once winter rainscommenced, some Black-bellied Plovers left the lagoonas the tide was rising(often before our censuseswere completed)to forage later at high tide in nearby pastures. At Abbott's numbersdeclined markedlyafter late Nov and remainedgenerally low but irregularthereafter (Fig. 23). This declinemay have been causedby regionalmovements of birdsaway from Abbott'sas runofffrom winterrains inundated the lagoon'sfiats, rather than by the departureof long-distancemigrants. Winter inter-sitemovement in our studyarea, perhapsexplaining the irregularhigh winter countsat Abbott'sand 194 WATERBIRDS AT POINT REYES

Limantour (Fig. 23), can be expectedsince Black-belliedPlovers arrive on and depart from the Farallonesthen (DeSanteand Ainley 1980). Spring migration extendsfrom mid- or late Mar throughMay (Jurek1973, ABN), althoughthis was not readily apparent from numberson the Point Reyes wetlands(Fig. 23). Numbersat Bolinasdropped suddenly in late Apr and reachedyearly lows in Jun (Fig. 23). During the study,winter numbersincreased at Bolinasand Limantour (Fig. 14). Exposedtidal flats are the mostimportant habitat for thisspecies, and at Bolinas flats of intermediate substrate texture are used more than sandier or mud- dier ones(Page et al. 1979). Sand beaches,fiat rockyshores such as Duxbury Reef,and rain-soakedpastures at hightide are alsoused. LesserGolden-Plover (Pluuialis dorninica) A very rare fall transient,winter resident,and springtransient (Fig. 12). Two subspeciesof Golden-Plovers,perhaps separate species(Connors 1983), are found in California:P. d. fulva, which breedsin Alaskaand Siberia,and P..d. dominica,which breeds in Alaskaand arcticCanada (AOU 1983). Fall migrants were detectedfrom late Jul to mid-Nov(Fig. 12). Six birds(race unknown) at Abbott'son 8 Dec 1965 may have been late migrantsor winteringbirds from nearby. Juveniles,dominica as early as 22 Aug (SNGH) and fulva by 13 Sep (JM), predominatedover adultsduring the peak of fall migrantsfrom earlySep to early Nov (Fig. 12, unpubl.data). Apparentlythe latestCalifornia specimen of dominicawas collectedon 11 Nov (Chaniot1966). However,sight records sug- gestthis race may remainwith winteringfulva until mid-Dec(DS). Migrants(race unknown)have lingeredto 31 Dec 1975, 14 Dec 1982, and 3-8 Jan 1981 at the FarallonIslands, where the speciesdoes not winter (DeSanteand Ainley 1980, ABN). Maximumcensus counts of fall migrantswere 11 birdson 29 Sep 1969 and 8 birdson 8 Nov 1979 at Limantour. Our only estuarinewintering records were of singlebirds at Bolinason censusesthrough the winterof 1974-75, and at

2000

1500---

-- 1000 --

500

1972-76 1977_81• I JunI Ju I I AugI SepI OctINov IDec I JanIFeb I MarI AprI Mayl

Figure24. Mean numberof AmericanCoots at BolinasLagoon from 1972 to 1976 and from 1977 to 1981.

195 WATERBIRDS AT POINT REYES

Limantourthrough the winter of 1968-69 (JS et al.) and on 20 Dec 1986 (JGE). Althoughsmall numbers of fuloa winter annuallyat scatteredsites on the coastal slopeof California(ABN, Garrettand Dunn 1981), two sitesin the Point Reyes area are among the few long-standingwintering sites. As many as 27 fuloa (usually 5-10) winter annuallyin the plowed fields and pastureson the Hall and Spalettaranches west of Drake'sEstero (ABN). Up to 15 birds(usually 4-6) have wintered since at least the late 1960s at a moist, marshy-edgedpasture at Lawson'sLanding, Dillon Beach,Tomales Bay (ABN); thesebirds also sometimes useadjacent tidal fiats. Winteringbirds have lingeredat Lawson'sLanding until 6 May (AB 42: 478) and on outer Point Reyesuntil 5 May (AW). During spring migratonin Apr and May (Jurek 1973, ABN), Golden-Ploversoccur much less regularlythan in fall. P. d. fuloa is the only race confirmedin Californiain spring, althoughspecimens exhibiting intermediate characters have also been collected and dorninica has been collected at that season on the Pacific coast of Mexico (Chaniot1966). The only localsummer record is of one bird at Abbott'sLagoon on 22 Jun 1966 (PRBO),reflecting the species'extreme rarity at that seasonany- where in California (McCaskie et al. 1979, Garrett and Dunn 1981, ABN). Golden-Ploversare found on plowedfields and grazedpastures, estuarine tidal flats,and occasionallyon sandbeaches during migration.

Snowy Plover(Charadrius alexandrinus) An uncommon summer resident and breeder and a common winter resident (Fig. 25). The Californiacoastal wintering population is about 2.6 times the size of the breedingpopulation (Page et al. 1986). The localpopulation is madeup of year-round residents,migrant breeders, and winterers (Warriner et al. 1986). Migrant breedersmay arrive in early Jan but most come from early Feb to late Apr. Othersarrive later, for secondnesting attempts, from earlyMay to earlyJul. Breedersdepart betweenlate Apr and late Nov, the earliestmoving to other sites for secondnesting attempts and the later onesto moltingand/or winteringareas. Surveysin 1977 and 1989, respectively,found 1 and 0 adultsat Bolinas,8 and 0 at Limantour,2 and 7 at Drake's Beach, and 29 and 17 on Point ReyesBeach, mostlyaround Abbott's Lagoon (Stenzel et al. 1981, PRBO unpubl.). Wintering birdsarrive between early Jul and earlyNov (mostin Jul)and departfrom mid-Feb to early May. From 1979 to 1984 an averageof 38 SnowyPlovers wintered at Dillon Beach,64 at Point ReyesBeach (mostly around Abbott's Lagoon), 92 on Drake'sBay (Limantourand Drake'sesteros combined), and 29 at Bolinas(Page et al. 1986). Color-markinghas shownthat winteringbirds are derivedfrom the Great Basinand the coastnorth and southof Point Reyesand that individualsshift betweenareas so that the compositionof winteringbirds at any locationvaries temporally. In historicaltimes human development, recreational use of beaches,and plant- ingsfor dunestabilization have lowered the sizeof the coastalbreeding population, especiallyin southernCalifornia (Page and Stenzel 1981), where the wintering populationhas alsodeclined since at least 1962 (Pageet al. 1986). The coastal breedingpopulation is currentlybeing considered for federallisting as threatened or endangered. SnowyPlovers roost in flocksin open placeson wide beacheswith birdsoften huddlingin human footprints or behind debristo get out of the wind. Both breeding and wintering plovers prefer spits adjoining wetlands, dune-backed beaches,and pocketbeaches over bluff-backedbeaches (Stenzel et al. 1981, Page et al. 1986). They forageon sandbeaches and on tidalflats when available.

196 WATERBIRDS AT POINT REYES

SNOWY PLOVER (A)

I JunI Ju I I AuglSepl Oct INov I DecI JanI FebI MarI AprI •aYI

SNOWY PLOVER (B)

I JunI Ju I I AuglSepl Oct I NovlDecI Jan I FebI MorI AprI MaY' SNOWYPLOVER(L)150 KILLDEER (B) I

578 I JunI Ju I I AuglSepl Oct INov IDec I JonlFeb I MarI AprI •aY I 479

?Sin SEMIPALMATEDPLOVER (A) AMERICANAVOCET (B)

• ,

IJunlJul I AugI SepI Oct I NovIDec I JanI FebI MarI AprI MayI I JunI Ju I I AuglSepl Oct I No¾1DecI Jan I Febl MarI A

Figure25. Seasonalabundance of someplovers and the AmericanAvocet in wetlandsof PointReyes. See Figure4 for details. 197 WATERBIRDS AT POINT REYES

SemipalmatedPlover (Charadrius semipalmatus) A rare summervisitant, a common fall transient, a fairly common winter resident,and a commonspring transient (Fig. 25). During fall migrationadults arrive in early Jul and juvenilesarrive as early as 2 Aug (Page et al. 1979). Numberspeaked in late Aug and early Sep, and migrationwas evidentuntil mid- Oct at Bolinas and Limantour (Fig. 25). The late Nov decline in numbersat Abbott's(Fig. 25) may have representeda local shiftof birdsdue to risingwater levelsafter the onsetof winterrains rather than a departureof migrants.In winter SemipalmatedPlovers were virtuallyabsent at Bolinasand irregularat Abbott'sbut regularat Limantour(Fig. 25), Drake's (Dec-Feb 1979-80 and 1980-81 mean 2.6), and TomalesBay (DS). The highestwinter censuscount was 41 birdsat Limantouron 3 Jan 1970, and the highestnon-census count was 45 at the south end of TomalesBay on 23 Jan 1981 (DS). From 1970 to 1988, the median number on the Point ReyesCBC, which providesa reasonableestimate of the entire Point Reyeswintering population, was 51 (range 13-124). Spring migration spannedApr and May (Fig. 25). At Bolinasspring migration was more pro- nouncedthan fall migration,in contrastto Limantourand Abbott's,where fall migrationwas more apparent(Fig. 25). In general,the springpeak is greaterat interiorCalifornia sites and the fall peak is greaterat coastalsites (Jurek 1973). On the Farallones,Semipalmated Plovers occur only in fall (DeSanteand Ainley 1980). On Point Reyesthey inhabitmainly tidal flatsbut alsouse sandbeaches (especiallynear estuariesand lagoons),plowed fields and pastures,and, during migration,pond margins. Numbersof winteringSemipalmated Plovers in the San FranciscoBay area increasedin the 1940s (Storer1951). Killdeer( Charadrius vociferus) A fairly common summerresident and breederand commonwinter resident (Fig. 25). Killdeersbreed from mid-Maruntil at leastJul on wetlandmargins and widelyin the interiorof Marin Co. (pers.obs.). Localbreeders and their offspring probablymade up the populationfrom earlyApr to mid-Sep(Fig. 25), when numberswere lowest. A Jun to Jul increase,especially noticeable at Abbott's(Fig. 25), may have representeda movementof locallyraised juveniles, and possiblyadults, from breedingsites nearby. A largerfall build-upat Bolinasfrom Sep to earlyNov (Fig. 25) coincideswith a late Sep to mid-Octmigratory peak on the Farallones (DeSanteand Ainley 1980) and fallswithin the state-wideAug to Nov migration period (Jurek 1973). The limited evidence of a fall peak at Abbott's and Limantour(Fig. 25) indicatesa low carryingcapacity for Killdeersthere at any season. A Nov to Dec dip in numbersat Bolinasand Abbott's (Fig. 25) may reflecta temporaryshift to agriculturallands, enhanced as Killdeerhabitat by the onsetof winter rains(see Black-bellied Plover). The shift from Abbott'smay have been augmentedby rising water levelsand that from Bolinasby high tides. However, this pattern might also be explainedby a passageof long-distance migrantsfollowed later by a secondinflux of hard-weathermigrants. Movement on the Farallones continues until at least Dec (DeSante and Ainley 1980). Winterersleave Point Reyes' wetlands chiefly in Mar (Fig. 25), as notedfor other coastalsites (Gerstenberg 1972), but departuremay beginby late Feb and continueinto Apr (Jurek1973, Fig. 25). Duringthe study,winter numbers at Bolinas were relativelyhigh during the drought years of 1975-76 and 1976-77 and declinedthereafter (Fig. 14). Killdeersfrequent fiat or gentlyrolling open terrestrialhabitats such as culti- vated fields,heavily grazed pastures (particularly when rain-soaked),and lawns. They also use pond and streammargins, tidal flats, where they seem to prefer muddyover sandy substrates (Page et al. 1979), and sandybeaches in the vicinity 198 WATERBIRDS AT POINT REYES of estuariesor creek mouths. They often nest near a sourceof fresh water. Killdeershave probably increased historically because of aõriculturalpractices that open up the land. Black-neckedStilt (Himantopus mexicanus) A ve• rare visitantwith only three censusrecords of sinõlebirds at Bolinas Laõoonon 21 Jan 1976 and 4 Apr 1977 and at Drake'sF_stero on 5 May 1981. Includinõcensus records, on PointReyes there are sixfall recordsfrom 29 Jun to 20 Sep, nine winterrecords from 20 Nov to 4 Feb, and six sprinõrecords from 4 Apr to 23 May, 1969 to 1988. All birdsexcept possiblyone were transients. AlthouõhJurek (1973) reportedthat the stilt'smiõrato• periodsin Californiaare from Auõ to Oct and from mid-Marto May, the aboverecords indicate that fall movement(perhaps includinõ post-breedinõ dispersal) beõins earlier and that some birdswander in winter. Earlyin the 1900s only smallnumbers of Black-necked Stiltscould be foundaround San FranciscoBay, fromsprinõ throuõh fall and irreõ- ularly in winter (Grinnelland W•he 1927, Grinnell and Miller 1944). In the 1950s and 1960s both nestinõand winterinõpopulations increased substantially in southSan FranciscoBay (Gill 1977, Coõswell1977, Riõneyand Riõney1981). Nestinõprobably did not beõinin north San FranciscoBay until after the mid- 1960s (R. Gill pers.comm.), and the numberof breedersthere stillappears to be increasinõ(ABN). In the MontereyBay area stiltnumbers have increased in winter sinceat least 1959 (Roberson1985). Continuedexpansion of the coastalpopulation is evidentfrom a sprinõ1984 influxof about40 birdsnorth to Humboldtand Del Norte countiesand the extensionof the breedinõranõe to near HumboldtBay in 1985 (AB 39: 958). The scarcityof stiltson Point Reyesprobably reflects a lackof suitablehabitat. Stiltshave linõered briefly here at sewerponds, freshwater ponds,and estuarinemarõins. Elsewhereon the centralCalifornia coast stilts foraõein the shallowwaters of saltevaporation ponds,'•louõhs, freshwater and brackishponds, sewer ponds, and floodedfields. American Avocet (Recurvirostra americana) A ve• rare summervisitant, rare fall transient,and commonwinter resident (Fiõ. 25). In California,fall miõrationextends from Jul throuõhNov and sprinõ miõrationextends from Mar throuõhMay, with the peak from late Mar throuõh Apr (Jurek 1973). In the Point Reyesarea avocetswintered reõularly only at Bolinas,Schooner Bay (Drake's F-stero),and BodeõaHarbor. On monthlywinter censusesin 1979-80 and 1980-81, up to 29 avocetswere foundat Schooner Bay and up to 12 were found at BodeõaHarbor. From 1970 to 1988 avocet numberson the PointReyes CBC (mostlyat SchoonerBay) ranõed from 0 to 20 (median3.5) exceptfor hiõh countsin three yearsranõinõ from 52 to 66. Other hiõh countsat SchoonerBay of 95 birdson 4 Oct 1966 and 102 on 14 Oct 1968 (PRBO)may have been mostly of fall transients.Counts of up to 81 birdsat Abbott'sbetween 7 Jul and 4 Oct 1966 were atypical;in subsequentyears we saw a total of four avocetsthere on three censusesbetween 14 Aug and 23 Dec. At Limantour we recorded a total of 12 on 16 censuses between 28 Jul and 26 Feb. Formerly,avocets were consideredirregularly common fall and winter visitors to San FranciscoBay (Grinnelland Wythe 1927), wherenesting was first recorded in 1926 (Gill 1977). Althoughavocets had begunto useSan FranciscoBay area saltponds by at least1899 (Grinnellet al. 1918), not until the early 1940s did the populationbegin to expand there to includelarge numbersof winteringand breeding birds (R. W. Storer 1951, Gill 1972b, 1977). Avocets have also increasedin winter in HumboldtBay since 1958, especiallyfrom 1961 to 1968 (Gerstenberg1972). A roughcomparison of breeding(Gill 1977) and wintering

199 WATERBIRDS AT POINT REYES

(R. W. Storer 1951) numbersin San FranciscoBay indicatesthat the winter population is substantiallygreater, as it is aroundMonterey Bay (Roberson1985). At Bolinasavocets have winteredregularly at leastsince 1971, and numbersthere increasedover the studyperiod (Fig. 14). Numberswere highestduring drought yearspresumably because of a shiftof avocetsfrom dried-upfreshwater habitats to marine habitats. In all yearswe suspectthe winterinflux reflected a localshift of avocetsfrom San FranciscoBay to BolinasLagoon feeding areas. Thesebirds probably move dailyto nighttimeroosts in San FranciscoBay sinceearly in the morningthey can be seenarriving at Bolinasfrom the south(Blick 1980). In the studyarea avocets useestuaries and lagoons,and at Bolinasthey concentrateon muddyrather than sandysubstrates (Page et al. 1979).

GreaterYellowlegs (Tringa melanoleuca) A very rare summerv•sitant and uncommonwinter resident(Fig. 26). Fall migrationextends from early Jul to Nov; springmigration extends from Mar to May (Jurek1973, Fig. 26). The earliestjuvenile recorded at Point Reyeswas seen on 8 Aug (SNGH). The greater regularityof winter sightingsat Abbott'sand Limantourafter Jan (Fig. 26) suggestslocal movements,perhaps influenced by changingwater levelsin freshwaterhabitats during winter rains. Spring passage was only weaklyevident on Point Reyeswetlands. Coastalbirds forage in shallow ponds,at marshedges, and along stream margins,as well as in saltmarshpools and waterover tidal fiats and channels,especially near freshwaterinflows.

LesserYellowlegs (Tringa fiavipes) LesserYellowlegs are very rare at all times,occurring primarily as fall migrants. One or two wintered at Bolinas from 1973-74 to 1979-80. Other census recordswere of one at Bolinasfrom 16 Jul to 24 Sep 1973 and one there on 12 Apr 1974, one at Abbott'sfrom 7 to 25 Aug 1975, one at Limantouron 13 Sep 1972, one there on 29 Mar 1968, and one to four there between11 and 27 Sep 1973. CumulativeMarin Co. records(Fig. 12) indicatean early Jul to early Oct fall migration,as in the restof the state(Jurek 1973). A sharppeak from mid-Aug to late Sep (Fig. 12) correspondswith the passageof juveniles(Garrett and Dunn 1981), which beginsas early as 29 Jul on Point Reyes(ABN: RS), or 21 Jul elsewhereon the northernCalifornia coast (AB 42: 1337). SingleLesser Yellowlegs have been recordedon only three of 19 Point ReyesCBCs from 1970 to 1988. A smallspring passage in Californiaextends primarily from late Mar to early May with an occasionalbird lingeringthrough Jun (Jurek 1973, McCaskieet al. 1979, Garrett and Dunn 1981). LesserYellowlegs were not recordedwintering in the San FranciscoBay area by Grinnell and Miller (1944), but they may have been overlookedamong the similarbut more numerousGreaters. LesserYellowlegs inhabitthe samerange of habitatsas Greatersthough presumably Lessers exploit somewhat shallower water.

Willet (Catoptrophorussemipalmatus) A common summer resident and a very common fall transient and winter resident(Fig. 26). A fall peak at Abbott'sand Bolinas,from late Jun to late Oct (Fig. 26), wasnot apparentat Limantour,where numbers increased gradually from Jun until Sep, when they reachedwinter levels. Fall migration in California extendsfrom late Jun to earlyNov (Jurek1973), and juvenilesarrive on the coast as early as 13 Jul (SNGH). Kelly and Cogswell(1979) reportedan Oct peak in San FranciscoBay and suggestedthat peaksof fall migrantsoccur progressively

200 WATERBIRDS AT POINT REYES 1:[,GREATER YELLOWLEGS (A) I JunI Ju I I AugI SeplOct INov IDec I JanI FebI Mc:rI Apr I MayI GREATERYELLOWLEGS(B) I JunI J u I I AugI SeploctlNov IDecI JoriI FebI Mo•I AprI AAoyl IJunlJulIAuglSeplOctlNovlDeclJonlFeblARorlAprlAAnY I 200[ WHIMBREL (B)

IJunlJul I AugI SepI OctIlqov IDec I JonI FebI ARorI Apr I M•YI

O&.. I JunI Ju • I AugI Sep I OcrI NovIDec I Je•I FebI/•ar I AprI/V•Y I

' WILLET(A)tJ[t•++++tE ttt IJunlJul I AugI $epI OcrI 1'.4orI Dec I JonI FebI/V•r I,Apr I AAoyI

WILLET (B)

•oo

+tt t•11' •+•Lt 75[ LON•-BILLEDCURLEW • 'B't o i Juni j ui iAuglSepl Ocli Nov iDec i jen i FebI Mc:r i Apr i May I

: I I I I WlLLET(L) IJun IJ u I I Augl SeplOct INøvIDec IJon IFeb IMc:r IApr IMay I

I LONG-BILLED CURLEW (L)

I Jun I J u I I AugI SepI Oct IlqovIDec I J•n I Feb I M•r I Apr I M•y I IJunlJul I AugI SepI Oct 11.4avI Dec I JanI FebI aRarI AprI AAoyI

Figure26. Seasonalabundance of the GreaterYellowlegs, Willet, and curlewsin wetlandsof Point Reyes. See Figure4 for details. / •. • 201 WATERBIRDS AT POINT REYES

laterfrom northto southalong the Californiacoast. This hypothesisis not corrob- oratedby our studysince peaks at Bolinasand Abbott's were in Augand Sep (Fig. 26), respectively,although both sitesare at roughlythe same latitudeas San FranciscoBay. Any latitudinaltrends could be masked,however, by the birds stagingat differenttimes at sitesat the samelatitude. Winter numbers at Abbott's fluctuated(Fig. 26), perhapsreflecting high seasonaland yearlyvariation in water levelsin the lagoon. Winternumbers at Bolinasdecreased during the study(Fig. 14). At Limantourand Bolinasthere was a suddenspring exodus in mid- to late Apr. The lackof a springmigratory peak in any of the wetlandscoupled with the scarcityof springmigrants on the Farallones(DeSante and Ainley1980) suggests there is little springmovement of Willetsalong the coastat this latitude;spring migrantsmay move directly from the coastto interiorbreeding sites. For the state as a whole,spring migration extends from Mar to late Apr (JurekI973). Willets feed on sandyand muddysubstrates of tidal flats(Page et al. I979), sandyand rockybeaches, and lagoon margins; unlike most shorebirds, they regularly feed in salt marshes(Stenzel et al. 1976).

WanderingTattler (Heteroscelus incanus) Becausetattlers prefer rocky shores along the outer coast,they were very rare fall and springtransients on the estuariesand lagoon. Fall censusrecords included one bird at Bolinason I Aug I973, up to II at Limantouron four datesfrom 28 Jul to 26 Oct (7 on 31 Aug I972), and at least I3 at Abbott'son sevendates from 28 Jul to 4 Sep (11 on 25 Aug 1975). Of the few juvenilesidentified, our earliestwas 14 Aug (DS), which compareswith the earliestdate of 9 Aug in Oregon (PaulsonI983). Our only spring censusrecord was of two birds at Abbott'son I May I980. Fall migrationon the northernCalifornia coast extends primarilyfrom mid-Julthrough Oct with an Aug to Sep peak (Jurek1973, ABN). Springmigration extends primarily from earlyApr throughMay. The only Point Reyes recordsfor Jun and early Jul are of two birds at Abalone Flat near Palomarinon 4 Jun 1981 (JGE)and one at Chimney Rock on 10 Jul 1982 (JGE). Migrantsand the smallPoint Reyeswintering population use primarilylow rocky reefs and sea stacksat scatteredsites along the outer coast. WanderingTattlers were formerly consideredto winter north only to Monterey Bay (Grinnelland Miller I944). We suspectthe discoverythat they now winter regularlynorth to Marin and Sonoma countiesand irregularlynorth to Humboldt and Del Norte counties(ABN) is a resultof more thoroughcoverage rather than a true changein status.

SpottedSandpiper (Actitis macularia) A rare fall transient,winter resident, and springtransient (Fig. 12). Up to three SpottedSandpipers regularly used Bolinas, where extreme dates of occurrence were 28 Jul (earlyfall) and 9 Jun (late spring). Small numbersalso winter on TomalesBay and on rocky beachesof Point Reyes' outer coast. The median numberon the Point ReyesCBC from 1970 to 1988 was 14 (range4-31). Fall migratorymovement was apparentfrom countsof at leastsix birdson nine censusesfrom 28 Jul to 16 Sep at Abbott'sand Limantour. Springmovement was apparentfrom high countsof eight birdsin early and mid-Mayat Bolinasand three birdson three datesfrom l I May to 5 Jun at Abbott'sand Limantour. In California,fall migrationprobably extends from earlyJul throughOct and spring migrationextends from mid-Aprto early Jun (Fig. I2, Jurek I973, Garrettand Dunn 1981). AlthoughSpotted Sandpipers are not known to nest in the study area, they havebred twice in Marin Co.--both timesalong the shorelineof San Franciscoand San Pablobays (PRBO unpubl.). They frequentrocky or gravelly 202 WATERBIRDS AT POINT REYES

shorelinesat estuaries,lagoons, and streammouths, rocky reefs and beaches alongthe outercoast, and the marginsof freshwaterponds and sewageponds. AlthoughSpotted Sandpipers may use channelmargins in estuaries,they avoid expansivetidal flats.

Whimbrel(Nurnenius phaeopus) A fairly commonsummer visitant, fairly commonfall transient,rare winter resident,and fairly common springtransient (Fig. 26). Non-breedersin summer overlappedwith fall migrants,which arrived by at leastearly Jul. The abbreviated Julto mid-Augpeak of migrants(Fig. 26) suggeststhat fewjuveniles pass through the area; passageof juvenilesbegins at leastby 22 Aug (SNGH). Fall movement continuedthrough Nov, and smallnumbers wintered irregularly at Bolinasand regularlyon the rockyouter coast of Point Reyes. The mediannumber on the Point ReyesCBC from 1970 to 1988 was 3.4 (range1-9). Springmigration extended from late Mar throughMay (Fig.26). Our earlyto mid-Mayspring peak is somewhat later than the mid- to late Apr peak reportedfor southernCalifornia (AFN 24: 644, Jurek1972). At PointReyes migrant Whimbrels feed on tidalfiats, salt marshes,sandy or rocky beaches,and in pasturesor ungrazedfields with low- growingvegetation. In winterthey inhabit primarily marine habitats.

Long-billedCurlew (Nurnenius americanus) An uncommonsummer resident and a fairlycommon winter resident(Fig. 26). ThroughoutCalifornia fall migration extendsfrom mid-Junto Oct and spring migrationextends from late Mar to earlyMay (Jurek1973). There were no peaks of migrantsat Limantouror Bolinas,but censusrecords at Abbott'sof 10 birdson four datesfrom 16 Jun to 4 Sep indicatea smallpassage of fall migrantsthrough the area. Identificationproblems have hinderedthe studyof the timing of juveniles'passage, but juvenilesarrive by at least 10 Aug (SNGH). The absenceof a spring peak at Point Reyes (Fig. 26) supportsJurek's (1973) suggestionthat coastalwintering Long-billed Curlews fly east in springtoward interior breeding areasrather than north along the coast. We cannotexplain why Bolinashas the only regularwinter curlewpopulation in the Point Reyesarea becausethe curlews' main prey items (Stenzelet al. 1976) are also availableon the other large estuaries. On Point Reyes curlewsfeed on tidal flats (except for the sandiestsub- strates),occasionally in salt marshes(Stenzel et al. 1976, Page et al. 1979), and rarelyin plowedfields or pastures.Historically, curlews have declined in California (Grinnellet al. 1918) and throughoutmuch of their breedingrange becauseof hunting and habitat loss (Palmer 1967, Johnsgard1981). Although there has been some recoveryfrom the effectsof hunting, numbersremain below historic levels (Grinnell and Miller 1944, Palmer 1967). In recent years curlews have apparentlydeclined in numbersto the north in HumboldtBay (Gerstenberg1972, Yocumand Harris 1975), but our censusdata showa stablepopulation on Point Reyes.

Bar-tailedGodwit (Lirnosalapponica) Our only recordof this vagrantto Californiais of a singlebird at Bolinasfrom 26 Oct to 2 Dec 1973 (AB 28: 101, Winter and McCaskie 1975, Page et al. 1979). A non-censusrecord for SchoonerBay, Drake'sEstero, on 28 Sep 1975 (AB 30: 120) wasrejected by the CBRC, and a 20 Sep 1988 record(AB 43: 163) is currentlyunder reviewby the CBRC. The acceptedBolinas record is among only six for California,1968 to 1984: four fall recordsof adultsand juveniles,11 Jul to 2 Dec, one winter record, 11 Feb to 2 Mar 1976, and one springrecord,

203 WATERBIRDS AT POINT REYES

3-5 Jun 1984 (CBRC). Limosa i. baueri, breeding in northern and western Alaskaand in northeasternAsia (AOU 1957, Johnsgard1981), normallymigrates southalong the westside of the Pacificin fall (Palmer1967).

MarbledGodwit (Limosa fedoa) A commonsummer resident and very commonwinter resident (Fig. 27). Peaks of migrantswere not evidentat Limantouror Bolinas,but at Abbott'sthere was a fallpeak from late Jun to earlyNov (Fig.27), correspondingto the 8 Julto 18 Oct spanfor fall transientsat the Farallones(DeSante and Ainley1980). Juveniles, difficultto agein the field,appear in fallby at least28 Jul (SNGH). The fallbirds at Abbott'scould have been southbound migrants or potentialwinterers forced out by risingwinter water levels. Althoughlittle migrationwas evidentat our census sites,birds may have been staging in springat morefavored sites such as Tomales and San Franciscobays, where springinfluxes have been noted (Jurek1973, 1974). Jurek(1973, 1974) reporteda noticeablenorthward movement in spring along the southern and central California coast as far north as the Point Reyes/Bodegaarea and that overlandmigration is directedto the northeast. Overall,godwit migration in Californiaextends from Jul to aboutOct in fall and from Mar to earlyMay in spring(Jurek 1973). Declininggodwit numbers from Jan to Feb at Limantour(Fig. 27), from Nov 1978 (2781) to Feb 1979 (899) and from Jan 1980 (1902) to Feb 1980 (820) at Bodega,and from Nov 1979 (1225) to Feb 1980 (761) at Drake'sEstero confirmed winter godwit movementsin this area. At HumboldtBay, Gerstenberg (1972) also found a post-Decdecline in godwit numbers. Kelly and Cogswell (1979) reportedprogressively later fall and winter peakstoward the southalong the Californiacoast, suggesting regional winter godwitmovements. Winter numbers at Bolinas and Limantour increasedover the courseof our study(Fig. 14). Godwitsforage on tidalflats (at Bolinasthey prefer areas of intermediatesubstrate texture,Page et al. 1979) and sandybeaches of the outercoast, infrequenfiy in salt marshes,and periodicallyin rain-soakedpastures. Many godwitsfeed at BolinasLagoon during the day and probablyroost in San FranciscoBay at night. We have observedflocks heading south over the oceanin the evening,and Blick (1980) reportedgodwits arriving at Bolinasfrom the southat sunrise.

RuddyTurnstone (Arenaria interpres) A rare summervisitant, uncommon fall transient,rare winter resident,and uncommonspring transient (Fig. 27). Non-breedersoccurred in Jun, and fall migrantsoccurred from early Jul until mid-Oct (Fig. 27). At bothBolinas (Fig. 27) and HumboldtBay (Gerstenberg1972) there are two peaksof fall migration,in late Jul and from late Aug to Sep. The firstpresumably reflects the passageof adults,the second,that of juveniles,which arriveas early as 15 Aug (Pageet al. 1979). BodegaHarbor, Tomales Bay, and Drake'sEstero were the only sitesin the PointReyes area with regularwintering populations. Bodega's wintering pop- ulationaveraged 29 birdsin 1978-79 and 45 in 1979-80; Drake'saveraged 2 from 1979 to 1981. From 1970 to 1988 the median number of Ruddy Turnstoneson the Point ReyesCBC was 17 (range 1-34); most birdswere on TomalesBay or Drake'sEstero. Springmigration extends from mid-Aprthrough May. A flock of 97 RuddyTurnstones at Limantouron 8 May 1980 was the largestwe recordedat any season.On PointReyes Ruddy Turnstones frequent gravelor rockybeaches, gravelly areas in estuaries,mussel beds, algae-covered tidalfiats, oyster-farm middens, and occasionallysand beaches littered with kelp. They sometimesforage in pasturesat Bodegaat hightide (DS).

2O4 WATERBIRDS AT POINT REYES

100 f MARBLEDGODWIT(A) I BLACKTURNSTONE (A)

t'l' ß' + - •',,, t •- •- •._-I.. i Juni j ut,1,i iAugi Sep ,iOct iNov iDec ,,i jan iFeb iMar i Apr ,1i May I I JunI Ju I I AugI SeplOct t NovIDec I JanI FebI MarI AprI May!

':[tt,,tMARBLEDGODWITttttt ,s,tt]tt]t]ttttttttl t 'øBLACKTtUtRtNtStTONE CB)11ttItt I JunI Ju I I AugI $epI OctI NovIOe½ I JoriI FebI,'•or I AprI MoyI

MARBLED GODWIT (L) "loo BLACKTURNSTONE (L) I

IJunlJul I AugI $epI OctINov IDec I JanI FebI MarI AprI MayI

I JunI Ju I IAugI SepI OctINov IDec I JanIFeb I MarI APrI MaY!

1 RUDDY TURNSTONE (A)

I JunI J u I I AugI SepI OctINov IDec I JanI FebI MarI AprI May! I JunI Ju I I AugI Sepl Oct It, k•v IDec I JanI FebI MarI AprI MaYI

IJunlJulI AugI Sep I Oct I NovI Dec I JanI FebI MarI AprI MaYI o , .If I JunI Ju I I AugI SepI OctINov IDec I JanIFeb I MarI AprI Mayl

RED KNOT (L)

01:4ß 4. •. 4.z.,..•.L+ L,. ,, J- 0 .+.• .L ß .L4. IJunlJul I Au91•,ep I C)c•'I Nov I DecI JonI FeBI McrI APrI MoYI I JunIJ u I I AugI SeplOct INovlDec I JanI FebI MarI AprI MayI

Figure27. Seasonalabundance of the Marbled Godwit, turnstones, and Red Knot in wetlandsof PointReyes. See Figure 4 for details. 2O5 WATERBIRDS AT POINT REYES

BlackTurnstone (Arenaria rnelanocephala) A very rare summervisitant and a commonfall transient,winter resident, and springtransient (Fig. 27). Non-breedersoccurred sporadically through Jun, and fall migrantsoccurred from earlyJul throughearly Oct (Fig. 27); juvenilesarrived as early as 20 Aug (Pageet al. 1979). Abbott'swas the only study-areawetland not usedby winteringbirds (Fig. 27). Spring migrationoccurred mostly in Apr (Fig. 27). BlackTurnstones use rocky reefs and seastacks along the outercoast, estuarinetidal fiats(especially around algal mats), and occasionallysand beaches litteredwith kelp.

Surfbird(Aphriza virgata) Thisrocky-coast species is a veryrare fall and spring transient on the estuaries. Our only censusrecords were of one bird at Bolinason 9 Oct 1971 and eightat Limantour on 21 Apr 1974. In the Point Reyes vicinity extreme dates for Surfbirdsare 12 Jul and 14 May; data on localfall arrivalof juvenilesare lacking but in Oregonjuveniles arrive as early as 26 Jul (Paulson1983). Roughly30 to 50 Surfbirdswinter in the Point Reyes-Bodegaarea (ABN, DS pers. obs.). Migrationin Californiaextends from mid-Julthrough Oct in fall and from late Mar throughearly May in spring;Surfbirds are sightedonly irregularly from mid-Mayto earlyJul (Jurek1973, McCaskieet al. 1979, Garrettand Dunn 1981). In spring, flocksof 20 to 60 birdshave been seenregularly on Point Reyes,but a flockof 155 birds at Drake's Beach on 29 and 30 Apr 1975 (EP, DS) was exceptional. Fall and winter flocksconsist usually of under 20 birds. Surfbirdsprimarily frequentrocky reefs, sea stacks,jetties, and occasionallytidal flats and sandybeaches duringmigration.

Red Knot (Calidriscanutus) An uncommonfall transient, very rare winter resident, and rare spring transient(Fig. 27). The only local (non-census)mid-summer record was of two birdsat SchoonerBay, Drake'sEstero on 16 Jun 1981 (DS). In fall adultfemales migratebefore males,which migrate before juveniles (Harrington 1982). On PointReyes fall migrationbegan in mid-Jul,juveniles arrived as earlyas 14 Aug (DS), peak numbersextended from late Aug to early Oct, and smallnumbers lingeredto lateNov or Dec (Fig.27); a highfall count was 200 at Bolinason 29 Oct 1973 (ABN: PJM). At Bodega,at leastfour knotswintered in 1978-79 and two wintered in 1979-80; at Drake's Estero, two wintered in 1979-80. Small numbersof knotsalso winter irregularly on TomalesBay, as indicatedby the Point ReyesCBC. Knots were recordedon 9 of 19 countsbetween 1970 and 1988; the mediannumber for the 9 yearswas 8 (range1-28). Thirtyat the southend of TomalesBay on 21 Jan 1979 (ABN: LCB) is the high mid-wintercount for the PointReyes area. Springmigration extended from mid-Aprto earlyJun (Fig.27); the highestspring count (non-census) was of 57 birdsat Bolinason 18 Apr 1976 (GWP, LES). Duringmigration knots typically stage in large numbersat restricted locations(Morrison et ai. 1980, Morrison1984), but the PacificCoast population is smalland knotslargely by-pass the Point Reyesarea. On Point Reyes,Red Knotsusually frequent tidal fiatsbut they sometimesfeed in pastureswhen tidal flats are inundated.

Sanderling(Calidris alba) A rare summervisitant and very common fall transient,winter resident,and springtransient (Fig. 28). Smallnumbers of non-breedersoccurred irregularly in 206 WATERBIRDS AT POINT REYES

Jun (Fig. 28). A pronouncedfall peak extendedfrom mid-Julto mid-Novat all wetlandswith juvenilesarriving as early as 21 Aug (Page et al. 1979). Winter numberswere relativelystable at Bolinasand Limantour(Fig. 28). At Abbott's, mid-winterand springpeaks (Fig. 28) reflectedlocal rather than migratorymove- ments. These peakswere causedmostly by storm-createdbreaches in the barrier bar which temporarilyexpose sizable sand flats where large foragingflocks concentrate. In six instances on censuses from 1973 to 1982, we recorded Sanderlingnumbers at Abbott'ssuddenly jumping from 200 to 500 birdsabove the previouscensus total when water levelsdropped after storms opened the lagoon mouth. As many as 1300 Sanderlings,a number of them banded at Bodega Harbor, convergedon Abbott's in Mar 1980 within four days of the lagoonbreaking open to the sea(Myers 1980). There wasa smallpeak of spring migrantsat Bolinasfrom mid-Aprto late May (Fig. 28) but none at Limantour. Sanderlingson the PacificCoast largely by-pass the Point Reyesarea in springand stagein large numbersin Oregonand southernWashington (Myers et al. 1984). Numbersof Sanderlingsat Bodegareach a peak in Dec, declineslowly through the winter,then drop rapidlyin spring(Myers et al. 1985). The fall increasethere involvesthe directarrival of long-distancemigrants, the return of birdsthat have stagedfor a monthor more on Point Reyes,or the returnof birdsthat were wan- deringwidely on the centralCalifornia coast after their initialarrival at Bodega. A Mar declinein numbersat Bodegaresults from localmovement of a large portion of the populationto Point Reyesrather than from migration,which extends from Apr or early May throughthe end of May. At Bodegaintense storms may sometimes cause numbers to plummet in mid-winter apparently because eroding beachesoffer Sanderlingslittle food (Myers1980). Censusstudies by J.P. Myersand associatesfrom 1976 to 1983 provideinfor- mationon numbersof Sanderlingswintering in the Bodegato Bolinasarea. The populationvaries between 500 and 700 birdsin the BodegaBay area, 225 and 450 at Dillon Beach, 400 and 675 at Point ReyesBeach (includingAbbott's Lagoon), and 400 and 650 in Drake's Bay (includingLimantour and Drake's Estero);it is under200 alongBolinas Bay (includingBolinas Lagoon). Sanderlings primarilyinhabit sandbeaches, sandy tidal fiats and, to a limiteddegree, rocky beaches. Densitiesare higheston sandbeaches linked with estuaries,and away from estuariesthey are higheron extensivebeaches than on shortbeaches (Myers et al. 1984). Around estuaries,birds typicallyconcentrate on sandy beachesat high tide, but on tidal flatsat moderateand low tides(Connors et al. 1981).

SemipalmatedSandpiper (Calidris pusilia) A very rare fall and springtransient. The three fall censusrecords were all from Abbott's:one adulton 4 Aug 1980 (DS),two juveniles from 16 to 18 Aug 1980 (DS),and one juvenile on 14 Aug 1981 (DS). The onlyspring records were of singlebirds at Bolinason 25 Apr 1979 (AB 33: 803) and at Abbott'son 16 and 17 Jun 1976 (AB 30: 884, Luther et al. 1979). Additional non-census recordsextend the date spanof Point Reyesfall recordsfrom 19 Jul to 24 Sep (ABN). First recordedin coastalnorthern California in 1968 (AFN 22: 644), SemipalmatedSandpipers have been sightedregularly in small numberssince 1977 becauseof observers'increased awareness (ABN). Fall recordsfor the northernCalifornia coast, mosfiy of juveniles,extend from 4 Jul to 2 Oct, with mostsightings from mid-Augto mid-Sep(ABN). Overall,in fall adults(females before males)precede juveniles (Morrison 1984). On the northernCalifornia coastjuveniles have arrivedas early as 18 Jul (AB 37: 1023), but they typically firstarrive from 22 to 25 Jul (ABN). Thereare sixspring records for the northern Californiacoast from 19 Apr to 24 May (ABN), the mid-JunBolinas record 207 WATERBIRDS AT POINT REYES // SANDERLING(A)

I JunI Ju I I AugI $epIoctlNov IDecI JanIFeb I MarI AprI MayI WESTERN SANDPIPER (B) 8O0 • tt,

SANDERLING (B)

I JunI J u I IAugI SeplOctlNov IDec I JanIFeb I MarI AprI Mayl ,t I JunI J u I I Augl SepIOct INovIDec I Janl FebIMar IApr IMayl 523 546

454õ

WESTERN SANDPIPER (L)

I JunI J u I IAugl SepI Ocli NovIDec I JanI FebI MarI AprI MayI

330a

WESTERN SANDPIPER (A) I JunI J u I I AugI SepI OctI NovIDec I Janl FebIMar IApr I MayI 'tt I JunI J u I I AugI SepIOcl. I NovI DecI Jan I Feb I Mar I Apr I Mayl

Figure28. Seasonalabundance of the Sanderlingand WesternSandpiper in wetlandsof PointReyes. See Figure4 for details. 208 WATERBIRDS AT POINT REYES

(above),and anotherof a bird at the Pajaro River mouth, MontereyCo., which remained through the summer of 1979 (AB 33:803 and 894). Coastal SemipalmatedSandpipers are found on lagoon margins, in estuaries,and at sewageponds. WesternSandpiper (Calidris rnauri) An uncommonsummer visitant and an abundantfall transient,winter resident, and springtransient (Fig. 28). Non-breedersoccurred irregularly in Jun at all sites; otherwiseseasonal patterns differed markedly from area to area. Bolinashad a well-definedpeak of fall migrantsfrom earlyJul to mid-Octand a verypronounced peakof springmigrants from late Mar to mid-May(Fig. 28). In fall,juveniles have beensighted at PointReyes by 28 Jul (DS). Elsewhereon the northernCalifornia coastjuveniles have arrivedas early as 19 Jul (ABN: KFC), but they normallyfirst arrivefrom 23 to 26 Jul (ABN). A very high counton one mid-Aprcensus was the onlyevidence of the passageof migrantsat Limantour(Fig. 28). At Abbott'sa smallJul peak (Fig. 28) coincidedwith the passageof adults,and was followedby a higherpeak in mid-Augthat coincidedwith the passageof juveniles.A decline in use of Abbott'sfrom Dec to Feb (Fig. 28) coincidedwith the floodingof sand fiatsas runofffilled the lagoon. Springmigrants used Abbott's irregularly in Apr. Malesprecede females in springmigration (Page et al. 1972). FemaleWestern Sandpipers winter farthersouth than males,and in California the latter greatly outnumber the former (Page et al. 1972). Most wintering Westernsat Bolinasare immaturemales, while most at Limantourare adult males (Pageet al. 1972, unpubl.data). In the studyarea WesternSandpipers primarily forageon estuarinetidal flatsand lagoonmargins and secondarilyon low rocky reefs,on beaches(especially at the marginsof ephemeralpools left by hightides), and in rain-soakedpastures. At Bolinas,Westerns forage in sandierareas than do LeastSandpipers (Page et al. 1979).

Least Sandpiper(Calidris rninutilla) An abundantfall transientand very commonwinter resident (Fig. 29). We did not record Least Sandpiperson any censusesin the first two-thirdsof Jun, althoughthe speciesoccurs irregularly then in northernCalifornia (McCaskie et al. 1979, ABN). On the basisof distinctpeaks at three censussites, fall migration extendedfrom late Jun/earlyJul to mid-Nov(Fig. 29). At Point Reyes,juveniles arriveas early as 27 Jul (SNGH) and elsewherein northernCalifornia as early as 23 Jul (ABN: RAE). This migrationperiod is broaderthan the late Jun to early Oct spanJurek (1973) reportedfor the stateas a whole. Springmigration, which begins in Mar (Jurek 1973) and continuesthrough mid-May, was not clearly reflectedby springpeaks in the studyarea (Fig. 29). At Bolinas,the lowestwinter averages (Fig. 14) were from the wettest years, 1972-73, 1973-74, and 1981-82 (Fig. 2), suggestingthat duringwet yearsbirds either fled adversecondi- tionson the estuaryor movedto enhancedfreshwater habitats, or that duringdry years birds concentratedon the estuary as freshwaterhabitats inland dried up. LeastSandpipers forage primarily on tidal flats,where they prefer muddiersub- stratesthan do Westerns(Page et al. 1979). They alsofeed in saltmarshes, on the marginsof freshwaterponds, in wet pastures,and to a limiteddegree on sand beachesand fiat rockyareas such as DuxburyReef.

Baird'sSandpiper (Calidris bairdii) An uncommonfall transientand very rare springtransient (Fig. 29). Fall migrants, mostly juveniles,were detected on censusesfrom 28 Jul to 5 Oct.

209 WATERBIRDS AT POINT REYES

There was alsoa singleadult on a 15 Jul 1972 Bolinascensus. Peak numbers werefrom mid-Augto mid-Sep(Fig. 29). Othernotable local fall recordswere of singleadults on outerPoint Reyes on 20 Jul 1986 and at Abbott'son 21 Jul 1986 (AB 40: 1250) and 20 Jul 1988 (AB 42: 1337) and a late bird on outer Point Reyeson 15 Oct 1972 (ABN: DDeS). The highestcounts were at Abbott's:19 on a 14 Aug 1975 census(LES,DS) and 20 on 5 Sep 1987 (non-census;ABN: LEASTSANDPIPER(A) •I I BAIRD'SSANDPIPER(A) IJunlJul I A.,,gI $ep I Oct I NovI DecI JanI FebI MarI AprI h•y I

IJunlJul I AugI SepI OctINov IDec I JanI FebI MarI AprI MayI iI BAIRD'SSANDPIPER(B) IJunlJul I AugI SepI Oct I NovI DecI JanIFeb I MarI AprI •1 LEAST SANDPIPER (B) 101BAIRD'S •ANDPIPER(L) I JunI J u I I AugI SepIOct INovIDec I JanIFeb I MarI AprIMayl

IJunlJul I AugI SepI Oct I NovI DecI JanIFeb I MarI AprI h•y I

I JunI Ju • IAugI SepI OctINov IDec I JanIFeb IMar I AprI k•l LEASTSANPIPER(L)0 '' JI f f• '"

•iI PECTORALSANDPIPER(A) I JunI Ju I I AugI $ep Jtt[I OctINovj [[JlJt[t[JJIDec I JonI FebI MarJtJI AprI MayI IJunlJullAuglSeplOctlNavlDeclJonlFeblMarlAprlk•lI JunI J u I I AugI Sep I Oct I•v IDe½I Jan I FebI •r I AprI • I

Figure29. Seasonalabundance of the Least,Baird's, and Pectoralsandpipers in wetlandsof PointReyes. See Figure4 for details. 210 WATERBIRDS AT POINT REYES

MFe). In fall, adultsmigrate mosfiy from mid-Julto earlyAug (femalesprecede males)and are followedby juveniles(Jehl 1979). Fall recordsfor coastalnorthern Californiaspan the period28 Jun-27 Nov (earliestrecord of a juvenile,18 Jul), but Baird'sSandpipers occur irregularly before late Jul and after earlyOct (ABN); thereare onlytwo Nov records(AB 32: 252). Ouronly spring census records were of onebird at Bolinason 8 Apr 1981 (AB 35: 859) andsix birds at Abbott'son 21 Apr 1982 (AB36: 890). The onlyother substantiatedPoint Reyesspring records are of one to threebirds at Abbott'sfrom 14 to 27 Apr 1977 (AB 31: 1043) and one at the Bolinassewer ponds on 10 May 1985 (RS). Baird'sSandpipers are now reportedalmost annually in spring on the northernCalifornia coast from 27 Mar to 12 May (ABN);also, there are three recordsof singlebirds from 2 to 18 Jun (AB 37: 1023, 41: 1483, 42: 1337). CoastalBaird's Sandpipers use tidal fiats, lagoon and pond margins, and sewageponds primarily and sandy beaches of the outercoast occasionally. PectoralSandpiper (Calidris rnelanotos) An uncommonfall transientand very rare springtransient (Fig. 29). Fall migrants,mainly juveniles, were recordedon censusesfrom 17 Aug to 6 Nov with a peak from mid-Septo early Oct (Fig. 29); non-censusrecords extended the occurrenceperiod to 16 Nov (ABN). The high censuscount was 17 birdsat Bolinason 5 Oct 1973, and the high non-censuscount was 32 at the Bolinas sewerponds on 25 $ep 1982 (GWP,LES). On censusesthe only verifiedfall recordsof adultswere of singlebirds at Bolinason 13 Jul 1971 and 25 Jul 1972 and at Abbott'son 17 Aug 1980. Non-censusrecords of adultswere of two birds at the Bolinassewer ponds on 20 Jul 1983 (JGE)and at Abbott'son 24 Jul 1988 (ABN: LJP). Fall recordsfor coastal northern California extend from 8 Jul to 4 Dec, but birdsoccur irregularly before mid-Aug (primarily adults) and afterearly Nov(ABN). The earliestrecord of a juvenileis for 13 Aug(ABN: RAE). Ouronly springcensus records were of singlebirds at Bolinasfrom 23 to 28 Apr 1973 (AB 27: 815) andon 21 Apr 1976 (B$o). The onlyother Point Reyes spring records are of one birdat BolinasLagoon on 9 Apr 1976 (GWP),another there from 17 to 24 May 1980 (AB 34: 812), oneto two birdsfrom 17 to 21 Apr 1976 (DS et al.)at the Bolinassewer ponds, and one at Lawson'sLanding, Dillon Beach, from 15 to 17 Apr 1986 (ABN:RHa). PectoralSandpipers occur irregularly in spring on the northernCalifornia coast from 4 Apr to 3 Jun (ABN). They are foundin salt marshes,on tidal flats,at sewageponds, and aroundfreshwater pond and lagoonmargins, especially where muddy or grassy. Dunlin(Calidris alpina) A very rare summervisitant and an abundantfall transientand winter resident (Fig.30). A fewbirds occurred irregularly from early Jun to earlySep (Fig. 30). Dunlinsreach California at leasttwo monthslater than mostother species of shorebirdsand, atypically for thisgroup, adult and first-year Dunlins arrive simultaneously.At Bolinasand Limantour,numbers rose rapidly to peakin Nov, then declinedgradually to mid-Apr,before dropping off sharplyin lateApr (Fig.30); Holmes(1966) recorded a similarpattern on SanFrancisco Bay. Springmigra- tion,evident from our data only by a declinein numbers(Fig. 30), extendschiefly fromApr to earlyMay (Jurek 1973). At Abbott's,Dunlins occurred primarily as fall migrants(Fig. 30), presumablybecause in wintersand flats there were flooded by runoff. Seasonaloccurrence patterns varied annually depending on rainfall(Fig. 31). Winternumbers at Bolinaswere highest during the droughtyears of 1975-76 and 1976-77, lowestin thewet years of 1972-73, 1973-74, and1981-82 (Figs.2

211 WATERBIRDS AT POINT REYES

2e69

DUNLIN (A)

IJunlJul I AugI S•p I Oct I NovI DecI JanI F•b I MarI Apr I MayI

I JunIJ u I I AugI SepIOct INov I DecI JanI FebI MotI AprI MayI

DUNLIN (B)

DOWITCHER SPP. (B)

.... IJunlJul IAugI SepI OctI hlovI Dec I JanI FebI MarI AprI MayI

IJunlJulI Aug I Sep I Oct I hlov I Dec I Jan I Feb I Mar I"Apr I May I

DUNLIN (L)

I DOWITCHERSPP. (L)

I JunI Ju I I AugI SepIOctlNov IDec I JanIFeb IMarI AprI MayI I JunI J u • I AugI SepI OctI NovI DecI JanIFeb I MorI AprI,Vay I

Figure30. Seasonalabundance of theDunlin and dowitchers in wetlandsof Point Reyes.See Figure 4 for details. 212 WATERBIRDS AT POINT REYES and 14). In the droughtyears birds may have moved from freshwaterhabitats that driedup to tidal areas,and in wet yearsmany may have remainedin freshwater habitats. Part of the reasonwhy numberswere high in the droughtmay have beenthat heavyrain in wet years,flooding mud fiats,induced the birdsto depart early,lowering the winteraverages for wet winters. For example,in Jan 1973, when severaldays of heavyrains and very high tidesinundated the tidal flatsfor most daylighthours, numbersat Bolinasfell sharplyfrom about 1000 to 300 birds,and remainedunusually low for the restof the season(Fig. 31). The departure in Jan 1973 coincidedwith 29 cm of rain in 10 days,the highesttotal during our studyfor a 10-dayperiod. Sincethis was also the onlylarge drop in numbers during our studyattributable to rainfall, it appearsthat Dunlinsremain on the estuaryexcept under extreme conditions. Dunlins feed on tidalflats, lagoon margins, freshwaterand sewagepond margins,and, to a limitedextent, on rocky reefs. At high tidesthey feed in rain-soakedpastures. At Bolinas,Dunlins, like Western Sandpipers, feed on somewhat sandier substratesthan do Least Sandpipers(Page et al. 1979). Saltmarshes are importantnighttime roosts. CurlewSandpiper (Calidris ferruginea) A very rare fall visitantfrom Asia with one censusrecord of a juvenileat BolinasLagoon from 7 to 14 Sep 1974 (AB 29: 114, Lutheret al. 1979). This is the only Point Reyesrecord and one of only 13 for California,1971 to 1987:12 in fall (adultsand juveniles) from 4 Jul to 1 Nov and one in springfor 27 and 28 Apr 1974 (CBRC).

6000 500 4OOO• 3000•1975-76 2000r ....1972-73 lOOOF I JunI J u I I AugI SepI Oct INov IDec I Jan I FebI MarI AprI • I

Figure31. Mean numberof Dunlinsat BolinasLagoon in 1972-73 and 1975-76.

213 WATERBIRDS AT POINT REYES

Stilt Sandpiper(Calidris hirnantopus) A very rare fall visitantwith one censusrecord of an adultat Bolinasbetween 7 and 13 Jul 1971 (AB 25: 902, Page et al. 1979). Another adult was at Limantour from 19 to 20 Jul 1985 (ABN: SNGH). There are additionalrecords for Point Reyesof about 10 individualsfrom 7 Aug to 22 Oœt;birds identified to age were all juveniles(ABN). On the northernCalifornia coast, extreme dates for fall transientsare 6 Jul and 8 Nov; most recordsare from mid-Augto early Oct, the time of passageof juveniles,which beginsat least by 17 Aug (ABN). In California,small numbers of Stilt Sandpiperswinter and remainthrough the spring onlyat the southend of the SaltonSea (Garrettand Dunn 1981). Awayfrom that localethere are only a handfulof Californiarecords of springmigrants from mid- Apr to earlyJun (Garrettand Dunn 1981, McCaskieet al. 1979). On Point Reyes Stilt Sandpipersuse tidal flats, lagoon margins,freshwater ponds, and sewage ponds.

Ruff (Philornachuspugnax) A veryrare visitantwith onlyone censusrecord, of juvenileat Limantourfrom 14 to 22 Sep 1980 (AB 35: 221, Binford1985). The three other substantiated Point Reyesrecords, all of singlejuveniles, are of one at Limantourfrom 30 Aug to Sep 1978 (AB: 33: 210, Luther et al. 1979); one at Abbott'sfrom 25 to 30 Sep 1986 (ABN: DDK et al.), and anotherfrom 10 to 11 Oct 1986 (DAH, SP). Nothern California Ruff records,which have increasedin frequencysince 1974 (ABN), extendfrom 15 Jul to 6 May (four recordsfor Jul one for May). Most occurrencesare in Sep and Oct and representmigrating juveniles, which arrive as earlyas 23 Aug (ABN).

Dowitchers(Lirn nodtorn us $pp.) Since all Long-billedDowitchers (L. scolopaceus)and Short-billedDowitchers (L. griseus)were not identifiedto specieson censuses,we have groupedthem for analysis. As a whole, dowitcherswere rare summervisitants, common fall tran- sientsand winter residents,and very commonspring transients (Fig. 30). Non- censusidentifications provided a reasonablyclear pictureof seasonaloccurrence for the two species. Dowitchersforage in estuaries,lagoons, and ponds. Long- billeds are found primarily in freshwaterhabitats, Short-billedsin more saline areas,although they occuralso in freshwater during migration (Pitelka 1950). On Point Reyes,Long-billeds are most numerousat pondsand at freshwaterinflows into estuaries. At Limantourand Bolinas,Long-billeds occur on muddiersub- stratesthan do Short-billeds(Lenna 1969, Page et al. 1979). Lenna (1969) reportedthat Long-billedsmove to estuarieswhen muddyfreshwater feeding areas are inundatedby winter rains. Short-billedDowitchers were very rare visitantsin the first two-thirdsof Jun. Migrationwas apparentby late Jun with the movementof adultsinto the study area; Short-billedsoutnumbered Long-billeds in fall. The earliestrecord of a juvenile Short-billedon Point Reyesis for 31 Jul (ABN: DAH), althoughjuveniles may occur on the coastas early as 23 Jul (Pitelka 1950). On the central California coast,adults are greafiyoutnumbered by juveniles,whose peak passageis from mid-Augto mid-Sep(Pitelka 1950, Lenna 1969, authors'unpubl. data). In contrast,on HumboldtBay, Gerstenberg(1972) reportedgreatest movement and two peaksduring the passageof adultsand a smallerand later passageof juveniles. This correspondswith the sequenceof fall passagein the Eastof adultfemales, then adultmales, and finallyjuveniles (Jehl 1963). The peak of over 20,000 dowitchers, most adults, on Humboldt Bay suggeststhat adults largely by-passthe

214 WATERBIRDS AT POINT REYES

Point Reyesarea; in the East, Short-billedsappear to stage in certain areas and avoidothers (Jehl 1963). Transientswere seenregularly on Point Reyesthrough mid-Oct and sometimeslingered until late Nov, when winter population levels were reached. Although Long-billedsgenerally outnumbered Short-billeds in winter in this area, the latter appear to be present annually, as indicatedby the following records: Bolinas--fiveon 27 Dec 1975 and singleson 11 and 23 Jan 1976 (GWP,LES); Limantour--one or two on 2 Jan 1978 (DS); BodegaHarbor--up to eight throughoutJan and Feb 1978 (DS), and 6 and 13 on 19 and 21 Jan 1979 (DS), respectively;Drake's Estero--up to 10 duringJan and Feb 1981 (DS), and two on 25 Jan 1982 (DS);Tomales Bay--singles on 17 Dec 1977, 16 Dec 1978, and 21 Jan 1978 (DS). The low numbersand irregularoccurrence in winterof Short-billedsat particular sites on Point Reyes may be a consequenceof California'sbeing at the north end of the species'winter range (Pitelka1950). Spring migrationbegan in mid-Mar (41 on 16 Mar 1976 at Bolinas),numbers peakedsharply from earlyto late Apr, and movementcontinued through May (Fig. 30). In contrast,others have reported two spring peaks, one in late Mar and another in late Apr (Lenna 1969, Gerstenberg1972). Short-billedsvastly out- numberLong-billeds on the coastduring spring migration. Long-billedDowitcher. The onlyJun recordswere of singlebirds on Bolinas Lagoon on 9 Jun 1976 (PRBO), at the Bolinassewer ponds on 12 Jun 1980 (DS), and on outer Point Reyes from 10 to 12 Jun 1988 (AB 42: 1337). Althoughadults normally appeared in mid-Jul(earliest 4 Jul), the main influx beganwith the arrivalof numbersof juvenilesin mid- to late Sep (Pitelka1950, Lenna 1969, authors'unpubl. data). Our earliestdate for a juvenilewas 4 Sep (DS), whichcompares with 26 Aug in Oregon(Paulson 1983). The end of fall migrationwas ill defined, becauseof the substantialwintering population, but migrationappeared to continuethrough mid-Oct, with stragglerstrailing into Nov. Our highestwinter censustotal was 158 birdsat Bolinason 6 Feb 1980. We sus- pect wintering birds in the Point Reyes area includeboth age classesbut that immaturespredominate, as Pitelka (1950) describedfor the coast in general; inlandthe oppositeis true. In Jan 1973, numbersat Bolinasdropped dramatically from 100 to 0, when 29 cm of rain fallingin a 10-dayperiod and stormtides flooded foraging areas for extended periods, a pattern like that found by Gerstenberg(1972) at HumboldtBay (see Dunlin account). No peak of spring migrantswas detectedin the Point Reyesarea, but occasionalsightings of small flocksof Long-billedDowitchers in localnon-wintering areas suggested that the springmigration period coincided with that of the Short-billed. CommonSnipe (Gailinagogailinago) A fairlycommon winter residentwith no obviouspeaks of migration(Fig. 32). The spanof datesof continuousoccurrence in the PointReyes area was 31 Aug to 11 May. Sightingsof singlebirds at the Bolinassewer ponds produced extreme datesof 28 Jul 1985 (AB 39: 958) and 24 May 1980 (AB 34: 812). For the northernCalifornia coast the early fall recordon 16 Jul 1983 at Lake Earl, Del Norte Co. (ABN: RAE) is exceptional,as are Jul recordsin general. The delay until Oct in the arrivalof snipesat Bolinas(Fig. 32) was due to the lack of freshwaterhabitat there before the winter rains. From 1972 to 1975, the four years with sufficientlyfrequent census data, snipesarrived in late Sep and their numbers builtup by mid-Octonly in 1972 and 1973, when the rainy seasonbegan in Sep (Fig. 2). Arnold (1981) notedthe importanceof severalheavy rains in fall before habitatbecomes suitable for snipes. At Bolinasthere was a sharpdecline in winter numbersbetween the droughtyears of 1975-76 and 1976-77. Subsequently, snipesremained well below their pre-1975 abundance(Fig. 14). 215 WATERBIRDS AT POINT REYES

At Bolinassnipes are restrictedto a complexof vegetatedbrackish ponds in salt marsh,Juncus-covered swales, and water-soakedpastures on the Pine Gulch Creek delta. The paucity of similar habitat at the other censusedwetlands explainedwhy numberswere lower there than at Bolinas(Fig. 32). Snipesmay concentratelocally elsewhere on Point Reyes,as 120 birdsdid near Olema Marsh

RED-NECKED PHALAROPE (B)

I JunI J u I I AugI Sepl OctItdov IOec I JanIFeb I MarI AprIMayl o I JunI J u I I AugI SepI Oct INov IDec I JanI FebI MarI Apr I Mayl ß ,o0[ 15øI COMMON SNIPE(B) I

IJunlJul I AugI SepI OcrI NovIOec I JanI FebI MarI AprI,v, ay I

RED PHALAROPE (A)

I JunI J u I I AugI SeplOct Itdov I DecI JanI FebI MarI AprI MayI I JunI Ju I I AugI Sepl Oct INov IOecI JanIFeb IMar IApr I Mayl

. •.1./T'l' RED-NECKED PHALAROPE (A) IJunlJul IAugl SepI OctINov IOec I JanI FebIMar I AprI MayI

10IREDol.. PHALAROPE(L)• .4, I JunI J u I I AugI SeplOct I NovIOec I JanI Febl MarI AprI May! I JunI J u I I Augl Sepl OcrINov IDec I JanI FebI MarI AprI MayI

Figure32. Seasonalabundance of the CommonSnipe and phalaropesin wetlands of Point Reyes. See Figure4 for details. 216 WATERBIRDS AT POINT REYES

on 2 Dec 1983 (JGE). They were foundroosting on dredgespoils when pastures nearbywere flooded. Typically,snipes frequent the muddyedges of freshwater marshesand swales,wet fields with relatively tall vegetation, and, to a lesser extent, wet close-croppedpastures. Salt marshesare little usedexcept in unusual circumstances,as describedfor Bolinas. Wilson'sPhalarope (Phalaropus tricolor) A very rare fall transientwith 26 birdson 15 censusesfrom 16 Jun to 15 Sep and a very rare spring transientwith two birds on 22 May 1981 at Abbott's. There are four other Point Reyesrecords in springfrom 3 May to 6 Jun (ABN); two recordsfor 12 June, 1977 and 1988 (ABN), are hard to classifyseasonally. The earliestrecord of a juvenileon Point Reyesis for 17 Jul 1988 at Abbott's (ABN: LJP). The greateradundance of fall migrantsis consistentwith the state- wide pattern (Jurek1973, McCaskieet al. 1979, Garrettand Dunn 1981, Swarth et al. 1982). Fall passagein coastalCalifornia extends primarily from mid-Junto mid-Sep(Fig. 12; Swarthet al. 1982, Jurek 1973, Garrettand Dunn 1981) with stragglersseen rarely through Oct; femalesprecede adult males which are followed by juveniles(Jehl 1988). Since 1980 there have been two Jan to Feb coastal northern Californiarecords at salt ponds(AB 34: 303, Roberson1985). Birdson springmigration pass primarily through the the SaltonSea and east of the Sierra Nevadaand mostlyavoid the coast. Springpassage extends primarily from mid- Apr to early Jun (Jurek1973); the earliestnorthern California spring record is 3 Apr (AB 41: 484). In spring migrationfemales apparently predominate early, maleslater (Oringand Davis 1966). On Point Reyes, Wilson's Phalaropes frequent freshwater, sewage, and brackishponds and occasionallytidal flats. They were formerlyquite rare in the San FranciscoBay area (Grinnelland Wythe 1927) but, sincethe creationand expansionof salt-pondevaporators in south San FranciscoBay startingin the 1860s (Ver Planck1951), their numbersin fall have increaseddramatically. Now tensof thousandscan be seenduring the peak of migrationin earlyJul (Swarthet al. 1982, Jehl 1988). The species'status in the Point Reyesarea appearsto be similarto that in the Bay Area beforethe creationof saltponds. Red-neckedPhalarope (Phalaropus Iobatus) A commonfall and springtransient (Fig. 32). Althoughnot recordedon our summer censuses,the specieswas an irregular visitant at that season; at the Horseshoe Pond 22 birds on 6 Jun 1981 dwindled to four or five birds that remained from mid-Jun through early Jul (DS). At Point Reyes wetlands,fall migrationspanned early Aug to late Oct and peaked in late Aug and early Sep (Fig. 32); a similarpattern was recordedon HumboldtBay (Gerstenberg1972). Locally,stragglers have remainedas late as 15 Dec 1979 at TomalesBay (AB 34: 659). In contrast,the fall build-upin the interiorat Mono Lake or at coastalsalt pondsbegins in late Jun or early Jul and peaksin late Aug (Winkleret al. 1977, Swarthet al. 1982, Roberson1985, ABN). On neriticwaters numbers build up at least by mid- to late Jul and peak in late Aug to mid-Sep (DeSanteand Ainley 1980, Stallcup1976, Briggset al. 1987, ABN). From mid-Augto mid-Sep1971, 93% of all birdsbanded at Bolinaswere juveniles(Page et al. 1979). In the same periodin 1980 the percentageof juvenilesin countsof 50-300 birdsat Abbott's increasedsteadily from 69 to 98% (DS). At Mono Lake from Jul throughAug, adultsoutnumber juveniles, which have been bandedas early as 3 Aug (Winkleret al. 1977); largenumbers of Red-neckedPhalaropes arriving in Jul on saltponds in San FranciscoBay (Swarthet al. 1982) are presumablyalso adults. The patternat favoredsites reflects shorebirds' typical pattern in fall of adultspreceding juveniles, 217 WATERBIRDS AT POINT REYES whereasthe pattern on Point Reyesestuaries primarily reflects the passageof juveniles. Adult femalesprecede males in fall migration(Orr et al. 1982). Fall numberson coastaland neritic waters fluctuatemarkedly from year to year (Stallcup1976, DeSanteand Ainley 1980, Briggset al. 1987, this study). Since 1974 healthyRed-neckeds have been found irregularlyin Jan and Feb on salt pondson the centralCalifornia coast (ABN, Roberson1985). In spring,Red-necked Phalaropes migrate mainly over the inshoreand offshore zones;only small numbers use estuaries, salt ponds, freshwater ponds, and sewage ponds (Fig. 32, Jurek 1973, Garrett and Dunn 1981, Swarth et al. 1982). Springmigrants occur primarily from mid-Aprto the end of May in all habitats; non-breedersmay remain into Jun or Jul, when they blendwith returningfall migrants. The springpeak in numbersis from late Apr to mid-May;Point Reyes' early date for a spring migrant is 3 Apr (GM); Monterey'sis 24 Mar (Roberson 1985). Numbersof springmigrants over inshore waters of centralCalifornia have peakedfrom 22 Apr to 19 May (ABN: BSa et al.). Red-neckedson oceanwaters generallyoccur closer to shore (within 50 kin) than do Red Phalaropes(Wahl 1975, Briggset al. 1984, 1987), and foragingbirds of bothspecies concentrate at surfaceconvergences that concentratezooplankton (Briggs et al. 1984). Migrants concentrateover the outermostshelf and upper continentalslope (Briggset al. 1987).

Red Phalarope(Phalaropus fulicaria) A fairly commonfall and springtransient (Fig. 32). in fall Red Phalaropes were foundon the estuariesirregularly from mid-Augto earlyJan but mosfiyfrom mid-Octto earlyDec (Fig. 32); extreme(non-census) dates were 6 Aug and 31 Jan (ABN). This species'fall migrationappears to be the mostprolonged of any of our shorebirds.Offshore the RedPhalarope u•_ally occurs from at leastmid-Jul to early Jan and the timing of peak numbersin the Farallones-PointReyes area varies annuallybetween late Aug and late Nov (DeSante and Ainley 1980). Overall,peak numbersin northernCalifornia are from Jul throughOct and for centralCalifornia are in Oct or Nov (Briggset al. 1987). In someyears the speciesremains numerous into Feb, with stragglers"wintering" from late Feb throughMar (Briggset al. 1987). in fall, femalesprecede males, which are followedby juveniles(Connors et al. 1979, Orr et al. 1982). The species'occurrence on estuarieswas irregularboth within and between yearsbecause Red Phalaropesgenerally do not strayfrom their principalmigration routeover offshore or oceanicwaters. Duringour censuses,influxes to the estuaries-up to 20-60 birds per day--occurredonly in Nov in 1973, 1976, and 1979. On 21 Nov 1976 an estimated10,000 individualswere on TomalesBay followinga severestorm (AB 31: 218). Not all fall influxescoincided with storms but all involvedsome emaciated adults and juvenilesthat were readilykilled by rap- torsand scavengers(unpubl. data). We had censusrecords of springmigrants from mid-Apr to earlyJun (Fig.32) and non-censusrecords from 16 Apr to 17 Jun (ABN). in northernCalifornia, Red Phalaropessometimes arrive by earlyApr, and stragglersmay lingerinto Jul (ABN). We recordedtrue springinfluxes of about 10-60 birdson censusesonly in 1975, 1979, and 1982. A non-census estimate of 4000 to 8000 birds on BoclegaHarbor on 25 May 1980 was by far the largestspring influx recorded (Connorsand Smith 1982). In spring,influxes usually followed several days of strong onshorewinds, and survivalof birds appearedto be much better than duringfall influxes.Strong onshore winds appear to be a necessarybut not suffi- cientcause of onshoreinfluxes of RedPhalaropes, as onshorewinds typically blow for extendedperiods in spring. Perhapswhen ocean food supplies are poor,birds 218 WATERBIRDS AT POINT REYES

are weakenedand more susceptibleto wind drift, or they are forcedto seekfood awayfrom the open ocean. Althoughsmall numbers of Red Phalaropesmigrate over inshorewaters of centralCalifornia in spring(peak dates of migrationrange from 6 to 18 May, ABN: BSa et al.), mostbirds pass farther offshore than Red- neckedPhalaropes (Wahl 1975, Briggset al. 1984, 1987). Most Red Phalaropes concentrateover the centralcontinental slope (10-75 km offshore,average 35 kin), but somebirds range to at least195 krn off PointReyes (Briggs et al. 1984). In winterbirds occupy waters mostly seaward of the continentalshelf (Briggs et al. 1987). Ocean-foragingbirds frequentzooplankton concentrations at surface water convergenceswhere strong thermal gradients border upwelling waters (Briggset al. 1984). Onshorethey forage on the water's surfaceor along the shorelinesof estuaries,lagoons, freshwater ponds, and sewageponds, and occasionallyon sandybeaches.

ParasiticJaeger ($tercorarius parasiticus) A very rare fall transientwith about20 birdson 17 censusesfrom 31 Aug to 14 Dec, mainly in Sep. Most sightingswere at Bolinas,where the jaegerswere frequentlyobserved pirating food from ElegantTerns, which are numerousthere. The occurrenceof ParasiticJaegers in the studyarea (Fig. 12) coincidedwith the fall passagein California,which extends from lateJul to late Dec and peaksin late Sep (Stallcup1976, McCaskieet al. 1979, Garrett and Dunn 1981, Roberson 1985). Parasitic Jaegers are found in small numbers in ocean waters off California in winter, in greater numbers in spring, and irregularlyin summer (McCaskieet al. 1979, Garrett and Dunn 1981). They are not recordedon the estuariesat theseseasons. The speciesis foundin neriticwaters out to 75 km, but mostlywithin 15 km of land(Briggs et al. 1987), and in estuarieswith concentrationsof ternsand gullsfrom whichthey piratefood.

Franklin'sGull (Laruspipixcan) A very rare visitantwith one censusrecord of an adult at Abbott'son 23 Jun 1976 (AB 30: 399). Non-censusrecords are of singlebirds at Abbott'sfrom 18 to 25 Aug 1966 (AFN 21: 74, PRBO) and at Hog Island,Tomales Bay, on 13 Aug 1989 (DS, JPK). Franklin'sGulls occur irregularlyon the northern California coastprimarily in fall from mid-Augto mid-Novand secondarilyin springfrom mid-Aprto lateJun (ABN). They occurcasually at othertimes of year.

Bonaparte'sGull (Larus philadelphia) A rare summervisitant, an abundantfall migrant, an uncommonwinter resident,and a very commonspring migrant (Fig. 33). Small numbersoccurred irregularlyin summerand usuallydwindled through the season. Fall migration extendedprimarily from mid-Oct through late Dec, peakingfrom mid- to lateNov. Over neritic waters numbersrise in Sep and Oct and peak in late Oct and Nov (Briggset al. 1987). Our highestestuarine counts of migrantswere after strong southwestwinds from 22 to 28 Nov 1974 with 11,600 birds at Bolinas and 45,000 at Limantour. Bolinaswas the only censusedweftand where Bonaparte's Gullsremained through the winter. Spring migrationextends from late Mar to earlyJun and peaksfrom mid-Aprto mid-May(Fig. 33, ABN). Over inshore watersof centralCalifornia, peak dates of migrationusually range from 21 to 24 Apr, but strongmovement exceptionally can startby 31 Mar (ABN: BSa et al.). Iramatures predominate at the end of spring movement. Off California, Bonaparte'sGulls migrate over the continentalshelf but mosfiywithin 40 krn of land(Briggs et al. 1987). Estuarinenumbers were quitevariable during migration 219 WATERBIRDS AT POINT REYES

as birdsveer from their over-oceanmigration path at irregularintervals during inclement weather to seek refuge or feed in the estuaries. At any season Bonaparte'sGulls may be foundin bays,estuaries, lagoons, and a varietyof freshwater habitats,especially sewage ponds.

957 311

'BONAPARTE'S GULL i=71

I JunI J u I I AugI $epI OcrINov I DecI JonI FebI MorI AprI/v•:• I Ijunljul I AudiSep I OcrINov IDec I JoriIFe• I •or I AprI • I

1160o 1564 • = 2•111 200

BONAPARTE'S GULL (B)

0 •'+ I JunI J u I I AugI SepI OcrI NaYI DecI JoriI FebI MarI AprI/v•:• I

I JunI J u I IAugI SepI OctlNovI DecI JanIFeb I MorI AprI Mayl

HEERMANN'S GULL (B)

127

BONAPARTE'S GULL (L)

IJunlJul I AugI $ep I OctI NovI DecI JonI FebI MarI AprI MayI I JunIJ u I I Augl$ep I OcrINov IDe½ I JanI FebI,•r I AprI/v•:• I

Figure33. Seasonalabundance of Bonaparte'sand Heermann's gulls in weftands of PointReyes. See Figure4 for details. 220 WATERBIRDS AT POINT REYES

Heermann's Gull (Larus heermanni) A very commonsummer to early winter dispersant(Fig. 33). Althoughour earliestlocal non-census record was for 24 May, in centralCalifornia northward springmovement may begin(very rarely) as early as late Apr (ABN);the increase in numbersoccurs progressively later to the north (Briggset al. 1987). Our ear- liestestuarine census record of 10 birdsat Bolinason 29 May 1973 coincided with a very early build-up of Heermann's Gulls and Brown Pelicansalong the northernCalifornia coast (AB 27: 914) followinga breedingfailure in the Gulf of Californiaattributed to anomalouslywarm water (Andersonand Anderson1976, D. W. Andersonpers. comm.). In most years Heermann'sGulls did not begin arrivinguntil mid-Jun,with the first major influxoccurring in early Jul (Fig. 33). Duringanchovy runs in late Aug and Sep of 1984 and 1985 from 2000 to 6000 Heermann's Gulls concentratedin BolinasLagoon for short periods. Similar peakswere not apparentat Limantourand Abbott's,which are muchless used by thisspecies than [3olinas.Numbers remained high on the wetlandsuntil late Oct, and only stragglerswere left by Dec (Fig. 33). Althoughin someyears a few birds remainthroughout the winteralong the PointReyes-Bodega coast (ABN), the only ones recorded during our study were up to I0 iramaturesat Bodega Harbor throughoutthe late winter and springof 1980 (DS et al.). Occurrencepatterns vary along the California coast, with greater winter numbersand earlier spring influxesfrom Montereysouth (Roberson 1985, Garrett and Dunn 1981). The pattern and timing of post-"breeding"dispersal of Heermann'sGulls are linked to water temperaturesas they affect food supply(D. W. Andersonpers. comm.; see also Brown Pelican). Since breedingHeermann's Gulls arrive at nestingislands in the Gulf of Californiain late Mar and beginlaying in earlyApr (Bent 1921), the Oct-Nov departurefrom northernCalifornia appears to be a responseto a seasonaldwindling of food suppliesand, perhaps more so, to stormyweather (D. W. Andersonpers. comm.),rather than migrationdirecfiy to the breedinggrounds. Heermann'sGulls feed in inshoreand offshorewaters, estuaries, and lagoons and sometimesbathe in freshwaterponds along the coast. Becausethey are klep- toparasiteson Brown Pelicans,the two speciesare very closelyassociated in the post-breedingseason. Grinnelland Miller (1944) noteda declinein Heermann's Gulls'abundance between 1915 and 1930 with a recoveryby 1943. Although Heermann's Gulls suffered the effects of DDT accumulation,disturbance, and eggingin the late 1960s and early 1970s, their populationsdid not declineas did thoseof the BrownPelican (D. W. Andersonpers. comm.). Mew Gull (Larus canus) An abundantwinter resident(Fig. 34) with censusrecords extending from 5 Oct to 5 May and non-censusrecords extending from 3 Oct to 18 May. Although not recordedin summeron Point Reyes,the Mew Gull occurscasually along the northern California coast then (ABN). Fall migration over the inshore zone extendsfrom earlyor mid-Octuntil at leastlate Nov (DS pers.obs.). Our wetland data (Fig. 34) suggestthat most Mew Gullswere transientsin the area, a pattern similarto that of the CaliforniaGull (Fig. 34). The Mew Gull graphsfor [3olinas and Limantourindicate a fall peak from Nov to mid-Jan,a mid-winterlow between late Jan and early Feb, and a springpeak from mid-Febto mid-Mar. In spring migrationadults precede sub-adults, which predominateat the tail end of migration. Mew Gullsare found primarilyon estuaries,lagoons, beaches, and inshore waters. Inshorethey are often associatedwith windrowsor tidal "rips"close to the shoreline(Briggs et al. 1987); they are casualoffshore (Wahl 1975). They also foragein wet pasturesafter heavyrain and in freshlyplowed fields within a few 221 WATERBIRDS AT POINT REYES

kilometersof the coast. Mew Gullsare only rarelyseen at refusesites (Cogswell 1974). Ring-billedGull (Larus delawarensis) A fairly common summerresident, a very common fall transient, and a commonwinter resident(Fig. 34). Summeringbirds were virtuallyall sub-adults. Our fall peakfrom Jul to Oct (Fig.34) reflectedthe movementof inlandbreeders to the central California coast and their subsequentdeparture for wintering groundsin southernCalifornia and westernMexico (Vermeer 1970). Juveniles arriveon the northernCalifornia coast as earlyas 16 Jul (AB 37: 1024). The lack of a pronouncedspring peak (Fig. 34) wasconsistent with the evidencethat spring migrationis primarilythrough the interior (Vermeer 1970). Conover (1983) reportedan approximately22-fold increasein the breedingpopulation of the westernU.S. in the last 50 years,which also implies a large increasein the West Coast'smigrant and wintering populations. On the coastRing-billed Gulls feed on protectedestuaries, lagoons, bays, beaches, freshwater ponds, plowed fields, pastures, playgrounds,and dumps. They are casualoffshore (Wahl 1975), rarely occurringmore than 1 krnfrom shore (Briggs et al. 1987). CaliforniaGull (Larus californicus) A fairlycommon summer resident, a verycommon fall dispersant,and a very commonwinter resident(Fig. 35). Virtuallyall birdssummering on the Point Reyesweftands were sub-adults.After breedingmostly at interiorsites, California Gulls travel to the Pacific Coast and fan out to both the north and south (Woodburyand Knight 1951), though dispersalat this time is predominantly northward(V. M. Norris and D. W. Winkler unpubl.data). Adultsand juveniles beginarriving on the northernCalifornia coast in mid-Jul,increasing numbers on the PointReyes wetlands (Fig. 35). The earliestdate for a juvenile,away from the recentlyestablished San FranciscoBay breedingcolony (Jones 1986), is 9 Jul 1981 (ABN: RAE), thoughdates of 20-25 Jul are more typical(ABN). Numbers on the Point Reyesweftands rose sharplyin late Sep and peakedfrom Oct until mid-Jan,when theydropped to mid-winterlows (Fig. 35). Cogswell(1974) and Johnston(1956) attributeda similar mid-Jan drop in numbersat San FranciscoBay trash dumpsto competitionfor food between CaliforniaGulls and largergulls, which arrive later at the dumps. However,sur- veysof coastalgulls by L. B. Spear(pers. comm.) show that in Oregonnumbers peak in Oct then drop sharplyto winterlows by Dec, that in northernCalifornia numberspeak in Oct but declinemore graduallyto winterlows by Jan, that in cen- tralCalifornia numbers peak in Novthen fall gradually to lowsin Feband Mar, and that in southernCalifornia numbers peak in Dec and fall to lowsby May. These observationssuggest that CaliforniaGulls drift southduring late fall and early winter,a patternalso noted for gullson oceanwaters off Californiaby Briggset al. (1987). V. M. Norrisand D. W. Winkler(unpubl. data) studied this phenomenon by analyzingband recoveries.Their data indicatean initialconcentration of both adultsand juveniles to the northoff Washingtonand a progressiveshift of the pop- ulationsouth from Aug throughFeb (peakmovement in Oct and Nov),with sub- adultsgenerally moving farthest south. SinceCalifornia Gulls initially shift north on the coastand later retreatsouth at roughlythe sametime that BrownPelicans, Heermann's Gulls, and ElegantTerns do (seeaccounts), all thesespecies appear to be respondingto changesin ocean productivitystimulated by the upwellingthat occursprogressively later to the north on the coast in spring and summerand declinesin late summerand fall (see habitat preferencesbelow and Resultsand Discussion).The southwardshift to

222 WATERBIRDS AT POINT REYES

exploitthese seasonal changes in foodsupply may have kept California Gulls from competingwith largergulls as the formershift their rangesouth of the latter's duringa periodof diminishingfood supplies. Vew largenumbers of California Gulls"winter" in the Gulfof Californiaand along the BajaCalifornia coast, and they may respondto southernoceanic conditions somewhat as Brown Pelicans andHeermann's Gulls do (D. W. Andersonpers. comm.). MEWGULL(A)I .• •.• RING-BILLEDGULL(A)

4464

I JunI$ u I I A•gl Sepl OctIlq• I DecI JonI FebI M=rI AprI/• I

MEW GULL (B)

1•oo

I Junl Ju I I •1 seplOctl• IDec I JonlFebl •IA•I•I

MEW GULL

I JunI Ju I I AugI SepI OctINov IDec I JanI FebI MarI AprI Ma•!

I JunI Ju I I AuglSepl Oct I NovI DecI JanI FebI/•ar I AprI Mayl

Figure34. Seasonalabundance of the Mewand Ring-billed gulls in wetlandsof PointReyes. See Figure 4 for details.

223 1200 .-' CALIFORNIA GULL (A)

1000 50 HERRINGGULL(A) /

8OO

I JunI Ju I IAugI SepI Octl NovIDec I JanIFeb I MarI AprI MayI 6O0

4OO

2O0

'J' + .I.'e' i Juni j u i iAugi Sep i Oct iNov i Dec i Jan i Feb iMar i Apr i May I IJunlJul I AugI SepI OctINov I DecI JanIFeb I MarI AprI MayI

26O( CALIFORNIAGULL(B)

IJ.nlJul IAugI $epI OcrINov I DecI JanI FebIMar I AprI MayI 303WESTERNGULL (A) I JunI Ju I IAugI SepI OctlNov IDec I JanIFeb IMar IApr I MayI

CALIFORNIA GULL (L) I JunI J u I I AugI Sep I OctlNov I Dec I JanI FebIMar I AprI MayI

WESTERN GULL (B)

IJunlJul IAugI SepI OctINov IDec I JanI FebI MarI AprI MayI $ Jß 4ca 43• IJunlJul I AugI Sep I OctI NovI DecI JanI FebI MarI AprI MayI

30a WESTERNGULL (L) THAYER'S GULL (B)

IJunlJul IAug I Sep I Octl Nov IDec I Jan I Feb IMar I Apr I Mayl IJunljuI IAug I Sep I OctlNov I DecI jan I Feb IMar I Apr I May I Figure35. Seasonal abundance ofsome large gulls in wetlands ofPoint Reyes. See Figure4 for details. 224 WATERBIRDS AT POINT REYES

Since in springthere are only smallpeaks of migrantsbetween Mar to May at coastalsites (Fig. 35, Cogswell1974, L. B. Spear pers. comm.), most adultsmust migratedirectly overland to interiorbreeding sites. Most sub-adultsremain on the coastand shift progressivelynorth (V. M. Norris and D. W. Winklerunpubl. data). On Point Reyessub-adults make up the bulk of the CaliforniaGulls by early May and they can be seen moving north at least through late May (DS) when low summernumbers are reached. Sub-adultscontinue moving north throughoutthe summer(V. M. Norris and D. W. Winkler unpubl.data), but the low summernumbers on Point Reyes (Fig. 35) suggestthat the magnitudeof movementthen is small. The northwardshift of sub-adultsin springagain puts them in a regionwith increasingfood supplies. Conover(1983) reportedthat the nestingpopulation of the westernU.S. has more than doubledin the last 50 years, implying also a large increasein the coastalpopulation. California Gullsfeed in estuaries,lagoons, and inshoreand offshorewaters. Off Point Reyesthey range as far seawardas the centralconti- nentalslope (Briggs et al. 1987). Offshorethey may outnumberall other species of gullsin the fall, with immaturesbeing particularlycommon in this zone (Wahl 1975). Non-marine foraging habitats include freshwaterponds and marshes, plowedfields, pastures, playing fields, parking lots, and dumps.

Herring Gull (Larus argentatus) A common winter resident (Fig. 35). The only local (non-census)summer recordswere of one bird at Limantouron 4 Jul 1965 (RS), a third-yearbird at Limantouron 5 Aug 1977 (AB 32: 353), and a first-yearbird at Dillon Beach on 3 Jun 1982 (DS); the Herring Gull occurscasually on the northern California coast in summer (ABN, McCaskie et al. 1979). At Bolinas and Abbott's numbers increasedfrom late Sep throughDec, peakedin Jan and Feb, and declinedin Mar and Apr. High Mar numbersat Limantourmay reflect a pulse of migrants(Fig. 35). On inshorewaters off Californianumbers peak from Dec to Feb (Briggset al. 1987). At the Farallonesthere appearsto be a minor fall peak in late Oct, pronouncedpeaks in late Nov and late Dec, and a sharp springpeak in late Mar, and a minor peak late Apr (DeSante and Ainley 1980). Garrett and Dunn (1981) reported that Herring Gulls move north in Mar and Apr in coastal southern California. On the coastHerring Gullsfrequent estuaries, lagoons, inshore and offshorewaters, garbage dumps, and, lesscommonly, freshwater habitats. At sea Herring Gullsconcentrate in neriticwaters, but appreciablenumbers also occupy waters over the continentalslope (Briggset al. 1987) and open ocean (Sanger 1970, 1973, Harrington 1975, Wahl 1975). Thayer'sGull (Larus thayeri) An uncommonwinter resident(Fig. 35). Thayer'sGulls were seenon censuses from 24 Oct to 18 Mar with most birds occurringfrom late Dec to early Feb. Extremenon-census dates for the studyarea are 13 Oct (JGE)and 9 Apr (GWP), exceptfor an immatureat Bolinasfrom 5 to 11 Aug 1986 (AB 41: 139). On the northernCalifornia coast birds may occasionallyarrive by late Sep (McCaskieet al. 1979), linger into May, and are casualin summer (ABN). Our highestcensus countswere at Bolinas,with 60 birds on 2 Jan 1975, 44 on 11 Jan 1977, and 54 on 8 Jan 1980. A large (non-census)count was of over 300 Thayer'sGulls in TomalesBay from 10 to 13 Jan 1985 (AB 39: 206); birdsthere were apparently concentratedaround spawningPacific Herring. Thayer's Gulls frequentdumps, estuaries,beaches, and inshoreand offshorewaters. The highestconcentrations in the San Francisco Bay area usuallyare at dumps, but, like Herring Gulls, Thayer'sare abundantonly in the absenceof WesternGulls (Winter and Erickson

225 WATERBIRDS AT POINT REYES

1977). Sourcesdiffer on whetherThayer's are commonor only casualoffshore (Sanger1973, Wahl 1975, Winter and Erickson1977). Western Gull (Larus occidentalis) A year-roundresident, very commonin fall and commonin winter,spring, and summer(Fig. 35). AlthoughWestern Gulls are not long-distancemigrants, their seasonaldispersals (Coulter 1975, Spear 1988) are reflectedby changesin numbersin the estuaries.They breedregularly along the coastin the studyarea and on the nearbyFarallon Islands, where about60% of the total Californiabreeding population is located (SowIs et al. 1980). Numbers on Point Reyes wetlands peakedfrom Aug to Oct (Fig. 35), when numbersare highestalong all of the Californiacoast, after post-breedingmovement from the Farallones(Spear 1988). Spear (1988) foundthat in late summerand fall mostiramatures move north from the Farallonesas far as Washington,then southof the Farallonesfor the winter. In years of poor upwellingand consequentlypoor ocean food supplies,many iramaturesgo southwithout first going north. Each springiramatures go north again until their third year, when they move close to the Farallones. Individual adultsdisperse each year to the samelocation where they remainduring the few monthsthey do not occupyterritories on the Farallones. Western Gull numbers on the wetlandswere lowestfrom Nov to Apr (Fig. 35) when iramatureshad dis- persedto the southand adultshad reoccupiedterritories on the Farallones;num- bersrose slightlyin May and Jun (Fig. 35), perhapsbecause of a later northward movementof sub-adultswhen upwellingintensified, increasing ocean food supplies. The WesternGull is a marine speciespreferring estuaries, lagoons, tidal reefs,beaches, and neritic waters. Although most birds stay within 50 km of land, a few rangeup to 95 km from shore(Sanger 1973, Harrington1975, Briggset al. 1987). WesternGulls regularly travel a few ki16metersinland to drink and batheat lakesand reservoirsand feed at dumps. See Spear(1988) for age- and sex-relatedhabitat preferences. Western Gull numbers at the Farallones reached a plateau in 1959 after reboundingrapidly from low populationlevels early in the centurycaused by humandisturbance (Ainley and Lewis1974). Presently,the Californiapopulation may be at an all-time high becausegarbage and fish offal produced by an expandinghuman population have increasedthe gulls'food resourcesand conse- quentlytheir survivalrate (especiallyof juvenilesand sub-adults)in winter (Ainley and Lewis 1974, SowIset al. 1980, Spear et al. 1987). The recentclosing of many San FranciscoBay area dumpsmay reversethis trend.

Glaucous-wingedGull (Larus glaucescens) An uncommonsummer resident and a commonwinter resident(Fig. 36). Virtually all oversummeringbirds in the Point Reyes area were iramatures. Althoughfirst-year birds may reach the northernCalifornia coast by 14 Sep(ABN: RAE, GSL),substantial influxes of birdsto PointReyes began in Oct (Fig.36). At the Farallones,in fallthere is a peakin lateNov and in springin lateMar (DeSante andAinley 1980), justbefore numbers at two censussites on PointReyes declined (Fig. 36). Glaucous-wingedGulls prefer estuaries,lagoons, beaches, tidal reefs, neriticwaters, and especiallygarbage dumps. They are also seen in moderate numbersin pelagicwaters, with iramaturestending to occurfarther from shore than adults(sanger 1973, Harrington1975, Briggset al. 1987). Interbreeding betweenthis speciesand the WesternGull has been documentedin the area of sympatryfrom southernBritish Columbia to Oregon(Scott 1971, Hoffmanet al. 1978). Birdsexhibiting characters intermediate between these two specieswere seenregularly in smallnumbers on our censuses. 226 WATERBIRDS AT POINT REYES

I 300 ELEGANT TERN (B) i juni j ui i A.u91 $ep i Octi Novi Deci Jani Febi/•r i A.pr i ,V,ay I

I JunI Ju I IAugI SepI OctIhlov IDec I JanIFeb I MariApr IMDyl IJunlJul IA.u9 I $epI Oct I NovI DecI Jo• I f:e• I MarI .•,prI ,V,ay I

GLAUCOUS-WINGED GULL (L)

IJunlJul I AugI $epI Oct I NovI DecI JanI FebI MarI AprI MayI

IJunlJul I Au91$ep I Oct I NovI DecI ,IonI Feb I Mar I Apr I/V•ayI

FORSTER'S TERN (A)

IJunlJul I AugI $epI Oct I NovI DecI JanI FebI MarI AprI MayI

2oo FORSTER'STERN (B)

I JunI J u I IAugI $epI OctINov IDec I JanI FebI MarI AprI Mayl

FORSTER'STERN(L) I JunI J u I IAugI Sepl Oct INov IDec I Jan I Feb I Mar I Apr I Mayl I JunI J u I I AugI Sep I Oct INov I Dec I jan IFeb I Mar I Apr I Mayl Fiõure36. Se;•son;•l;•bund;•nce of the Gl;•ucous-winõedGull ;redsome terns in wetl;•ndsof PointReyes. See Fiõure 6, for det;•ils. WATERBIRDS AT POINT REYES

GlaucousGull (Larus hyperboreus) A very rare visitantwith one censusrecord of one bird at Abbott'son 6 Dec 1975 (DS, JGE). GlaucousGulls are now reportedalmost annually from Point Reyeswaters on datesspanning 20 Oct to 21 May (ABN); the only adultwas at TomalesBay on 12 Dec 1976 (AB 31: 369). Thisspecies is rarethe lengthof the Californiacoast from late Nov to early Apr and is irregularfrom mid-Septo late Nov and from early Apr to late May; stragglershave been recordedas late as 21 Jun (AB 39: 958). Almostall recordsare of iramatures,and most of theseare first-winterbirds (Devillerset al. 1971, McCaskie et al. 1979, Garrett and Dunn 1981). GlaucousGulls are foundat dumps,estuaries, and occasionallywell "offshore"(Harrington 1975, ABN).

Black-leggedKittiwake (Rissa tridactyla) A veryrare wetland winter visitant with censusrecords of 26 birdson 14 dates from 17 Oct to 29 Jun and scatterednon-census records in all months except Aug. Kittiwakesare pelagicbirds that associate with the coldlandward side of pro- ductivewaters of the transitionzone betweenwarm subtropicaland coldsubarctic watersfound well "offshore"of centralCalifornia (Ainley 1976b); they may occur in similardensities over shelf, slope, or oceanicwaters (Briggs et al. 1987). They typicallyshow up in coastalwetlands only when unusuallywarm oceansurface temperaturescause them to move to shore (Ainley 1976b). Black-legged Kittiwakesinhabit the open oceanoff Californiaprimarily from Sep to May and are most numerousfrom Dec to Mar (Ainley1976a, Stallcup1976, McCaskieet al. 1979, Garrettand Dunn 1981, Briggset al. 1987). After flightyears they also occurfrom Jun to Aug, althoughnumbers dwindle through this period. Our only May to Junrecords were for 1976 andfollowed an exceptionalinflux that left the highestnumbers of kittiwakesto datein latespring and summer on the coastof northern(AB 30: 999, ABN) and southernCalifornia (Garrett and Dunn 1981). Kittiwakenumbers in Californiawaters vary greafiyfrom year to year and are highestin yearswith winter oceansurface temperatures at or below normal (Ainley1976a); numbersare muchlower in E1Nifio years(Briggs et al. 1987). The timingof peakwinter abundance each year also varies greatly with seasonal variationin watertemperature (Ainley 1976a,b). The timingof northwardmovement alsovaries markedly, as indicatedby springcensuses of migrantsover the inshorezone of central California,where from 1977 to 1979 numberspeaked from 5 to 24 Mar but in 1976 they peakedon 15 May (ABN: BSa et al.). In 1976 very largenumbers of kittiwakesoccurred far off Californiain mid-winter when oceantemperatures were belownormal, but apparentlyunusually warm waters from mid-Feb to mid-Mar forced birds close to shore and precipitateda large die-off. This was followedby largenumbers of kittiwakeslingering into springand summerafter watertemperatures again fell belownormal (Ainley 1976b). Kittiwakesundertake a leisurelylong-distance dispersal from the breeding groundsrather than a truemigration (Coulson 1966, Ainley1976a). In 1976 and 1977, duringspring movement over the inshorezone of centralCalifornia, irama- tureswere threetimes as commonas adults(ABN: BSa et al.); althoughadults and iramaturesare equallyrepresented in oceanicwaters in winter,iramatures predom- inateclose to shore(Harrington 1975). CaspianTern ($terna caspia) A fairly commonsummer visitant, a commonfall transient,and a fairly commonspring transient (Fig. 36), with censusrecords from 22 Mar to 26 Oct and non-censusrecords from 16 Mar to 14 Nov (ABN). Before the 1980s

228 WATERBIRDS AT POINT REYES

CaspianTerns were casualon the northernCalifornia coast between late Oct and mid-Mar (ABN). In 1981 arrivalaveraged about two weeksearly at most locations,with the earliestbird notedon 19 Feb (AB 35: 332), and duringthe winters of 1985-86 through1987-88 therewere sightings of unprecedentednumbers of birds(3-10 per year)from Dec to Feb(AB 40: 326, 41: 324, 42: 316). The few birdsoversummering in the studyarea may be prebreeders(Ludwig 1965, Gill and Mewaldt1983) or perhapsbreeders on long-distancefeeding trips, sinceBolinas is within the 60-km foragingrange of adults(Gill 1976) from the nearestbreeding colony on San FranciscoBay in Napa Co. (Gill 1977). Breeding therelikely extends from early Apr to Sep,with the firstyoung fledging in lateJun (Gill 1972b, 1977, Ludwig 1965). The early Jul increasein numberson Point Reyes(Fig. 36) mayhave been the resultof adultsand young arriving from nearby breedingcolonies, given the timingof breedingand our frequentobservation of adultsfeeding fledged young; our earliestrecord of a juvenilewas for 2 Jul 1980 (DS). After fiedging,hatching-year birds disperse primarily to the north (Gilland Mewaldt1983). Springmigrants pause on the estuariesmostly in Apr and May (Fig. 36). A high springcount was 250 at Bolinason 26 Apr 1989 (KH). Peak datesof springmigration over inshore waters of the centralCalifornia coast range from 12 to 29 Apr (ABN:BSa et al.). Grinnelland Miller (1944) noteda slowrecovery in numberssince the era of the feathertrade prior to 1900. Sincethe beginningof this centurythe Pacific populationhas shiftedfrom nestingin numeroussmall colonies in inlandfresh- water marshesto nestingprimarily in large coloniesin human-createdhabitats alongthe coast(Gill and Mewaldt1983). Since1960 the Pacificnesting population has increasedby over 70%, and the San FranciscoBay populationhas increasedby about 27% (Gill and Mewaldt 1983). However,our 1973 to 1982 censusesindicated no marked change in the spring population at Bolinas. CaspianTerns at San DiegoBay appearto be sufferingfrom impairedreproduc- tive successdue to DDE accumulatedfrom their prey (Ohlendorfet al. 1985). CaspianTerns use estuaries, lagoons, and the immediateinshore zone, as well as freshwaterponds, streams, reservoirs, and marshes.They foragein the shallow water over mudflatsbut more frequentlyin tidal channels(Baltz et al. 1979).

ElegantTern (Sterna elegans) A common summerand fall dispersantfrom 24 Jun to 4 Dec with highest numbersfrom Aug to earlyOct (Fig.36). Exceptionalnon-census records are of fourbirds at Bolinason 26 Apr 1989 (ABN:KH) andone at TomalesBay on 14 Dec 1983 (AB 38: 353). A countof 135 birdsat Bolinason 24 Jun 1986 (RMS) washigh because only small numbers usually arrive before the maininflux in early Aug(Fig. 36). ElegantTerns dispersing north typically reach southern California, northof the Gulfof Californiaand San Diego breeding colonies, by lateJun and becomecommon in Jul(Garrett and Dunn 1981). Theygenerally arrive progressivelylater with increasinglatitude (ABN). Birdshave tended to arriveearlier in the seasonsince about 1977 (Garrettand Dunn 1981, Roberson1985), paral- lelinga northwardexpansion along the coast of thelimits of regularpost-breeding dispersaland an increasein latewinter and earlyspring sightings since the late 1970s (Cogswell1977, McCaskieet al. 1979, Morlan and Erickson1988). ElegantTerns have now beenseen on the northernCalifornia coast in every monthof theyear, and small numbers have been seen in Apr andMay since 1985 (ABN). Thesespring birds may be prospectingfor newnesting grounds, as they usuallyremain for shortperiods, Apr and May are too early for post-breedingdispersal,and the breeding range in southernCalifornia continues to expand(AB 41: 1488).

229 WATERBIRDS AT POINT REYES

Elegant Terns breedingat San Diego are highly dependenton Northern Anchoviesfor feedingchicks (Schaffner 1986), and movementsof ElegantTerns in Californiaare probablyclosely related at all timesto movementsof Northern Anchovies(E C. Schaffnerpers. comm.). Althoughoverall occurrence in northern Californiais similarto that at Point Reyes(Fig. 36), the timing of arrivalin the region is variable and somewhat earlier to the south in the Monterey area (Roberson1985, ABN). The ElegantTern's progressivelylater movementto the north and variabletiming of arrivalare strikinglysimilar to those of the Brown Pelican(and Heermann'sGull), anotheranchovy-dependent species (see pelican accountand Schaffner 1986). Timing of arrival may depend on patterns of anchovyabundance and oceanographicconditions, both at the breedingcolonies and in the northern areas to which the terns disperse(E C. Schaffner pers. comm.). The initialsize of Brown Pelicanbreeding populations generally varies littlefrom yearto year,but that species'reproductive success is highlyvariable and positivelycorrelated with anchovyabundance. In contrastto the pattern exhibited by pelicans,the breedingpopulation size of ElegantTerns is variableand positively correlatedwith anchovyabundance, but the reproductivesuccess of birdsthat do breedis generallyhigh (Schaffner1986). Hence, Brown Pelicansarriving early in centralCalifornia may representfailed breeders (see account) while ElegantTerns arrivingearly may representnon-breeders (E C. Schaffnerpers. comm.). In our studyarea largenumbers of ElegantTerns were foundconsistenfiy only at Bolinas (Fig. 36). Unusual numbers, such as 2500 on 7 Sep 1984, 2000-3000 from 26 to 28 Sep 1984, 3700 on 24 and 25 Aug 1985 (RMS),and over 6000 on 28 Aug 1985 (JGE),concentrated at Bolinasduring the very rare anchovyruns insidethe lagoon. Another high count was of over 2000 birdsin Drake's Bay on 29 Sep 1985 (ABN: JW). ElegantTerns occurredirregularly at Limantour (Fig. 36). During our censusperiod they were recordedat Abbott's only in 1981, a year of high anchovy abundance in southern and central California(Schaffner 1986), on six of sevencensuses from 20 Jul to 16 Sep; the high countwas I40 on 4 Sep. Before 1950 Elegant Terns ventured rarely and irregularly north to San Francisco Bay (Grinnell and Miller 1944). Then a dramatic increase began (Cogswell1977), includingestablishment of the San Diego colony in 1959 following the El Niho of 1957 and 1958 and coincidentwith increasinganchovy abundance(Schaffner 1986). Now large numbersof ElegantTerns are present regularlyalong the north-centralCalifornia coast in fall (McCaskieet al. 1979, Garrettand Dunn 1981). For manyyears large numbers dispersed north regularly only as far as the Point Reyesarea, but they now reach HumboldtCo. regularly (Morlan and Erickson1988). RoyalTerns (,.qterna maxima) formerlyoccurred as far north as TomalesBay (Grinnelland Miller 1944). When ElegantTerns increasedin California,Royals withdrewalmost completely from centralCalifornia and becameless abundant in southernCalifornia (Cogswell 1977, McCaskieet al. 1979, Garrett and Dunn 1981). Simultaneously, Pacific Sardine numbers in central and southern Californiawaters declined drastically, while Northern Anchovynumbers increased (Ainleyand Lewis 1974, Schaffner1986). ElegantTerns currenfiy have seasonal movementsroughly similar to the anchovy's(Schaffner 1985) and they have increasedtheir numbersand rangein Californiaapparently by exploitinganchovy increases. In centralCalifornia, Royal Terns likelydepended heavily on sardines, which were abundantformerly inshore (along beaches, and in estuariesand lagoons)but alsoranged to offshoreand pelagicwaters (Murphy 1966, Schaffner 1985). This dependenceis suggestedby the declineof the RoyalTern population at the time of the southwardretraction of the sardinepopulation (Schaffner 1985). See Appendixfor formerstatus of RoyalTern in the Point Reyesarea.

23O WATERBIRDS AT POINT REYES

Schaffner(1985) reportedthat in southernCalifornia the ElegantTern feeds farther "offshore"than the Royal Tern, which he consideredto be a warm-water speciesand primarilyan "inshore"coastal forager, as it is throughoutmuch of its range. In the Gulf of California,D. W. Anderson(pers. comm.) also notes that ElegantTerns are "pelagic"feeders and that RoyalTerns are "inshore"or near- shorefeeders. Briggset al. (1987) reportedthat ElegantTerns are rare more than 4 km from shorealong the Californiacoast and RoyalTerns are rare more than 1 km from shore. Our experienceat Point Reyesis that Elegantsforage in shallow water very closeinshore and insideestuaries, harbors, and lagoons. Grinnelland Miller (1944) reportedthat RoyalTerns forage "on the open ocean,mostly well offshore,"areas that had been lessintensively exploited by the sardinefishery (E C. Schaffnerpers. comm). Thus, these seeminglyconflicting reports of habitat preferenceprobably represent geographical differences in seasonalmovements of anchovies,historical expansions and contractionsof the anchovypopulations, and possibleseasonal observer biases.

Common Tern (Sterna hitundo) A very rare fall transient,with 48 birdson 11 censusesfrom 7 Aug to 26 Sep, and a very rare springtransient, with 17 birdson 8 censusesfrom 21 Apr to 29 Jun. Most censusrecords were for Abbott's,but Common Terns were also seen with regularityat TomalesBay (DS). Marin Co. recordsextend from 9 Apr (JGE) to 19 Dec (AB 26: 651) with a fall peak of migrantsfrom mid- to late Sep and a springpeak in mid-May(Fig. 12). Peakspring migration dates over inshore waters of the centralCalifornia coast range from 25 Apr to 12 May (ABN: BSa et al.). Migrationperiods in northernCalifornia extend from early Apr throughMay in spring(with stragglersin Jun)and from earlyJul to early Nov in fall (McCaskieet al. 1979, ABN). Common Terns are casualin northernCalifornia after mid-Nov (McCaskieet al. 1979), with the latestrecord being for 4 Jan (AB 38: 353). CommonTerns frequent estuaries, lagoons, and inshoreand offshorewaters. The general scarcity of the speciesalong the shoreline of most of northern California,especially in spring(ABN), contrasts with the situationin the Monterey area, wherethe speciesis common,possibly because there the deepwaters of the MontereySubmarine Canyon occur within a few milesof shore(Roberson 1985). This differencesuggests Common Terns migrateover deep neriticwaters at dis- tancesfrom shoreinfluenced somehow by underwatertopography. Briggs et al. (1987) reportedthat CommonTerns are mostnumerous within 25 km of shore. Forster'sTern (Sternaforsteri) A very rare summervisitant, a fairly commonfall transient,a fairly common winter resident,and a commonspring transient (Fig. 36). Forster'sTern is primarilya transientin the Point Reyesarea, althoughbirds winter in moderatenumbers at Bolinas(Fig. 36) and TomalesBay (DS, JGE) and in smallnumbers at BodegaHarbor (DS). Springmigration extended from earlyApr to late May and post-breedingdispersal and fall migrationextended primarily from mid-Julto mid- Oct, with stragglersto early Dec (Fig. 36). Migrationover inshorewaters of the centralCalifornia coast begins in mid- to late Mar (ABN),and peakdates range from 24 Apr to 13 May (24 to 28 Apr in threeof fouryears, ABN: BSa et al.). Breedingin SanFrancisco Bay extends from late Apr (Gill1972b, 1977) probably until Sep, with the first young fledgingin late Jun. In the Point Reyesarea Forster'sTerns were seen in only a few instancesduring the middle of the breedingseason, although they occurregularly at that seasonas closeas Tiburon in San FranciscoBay (BiL). Numbersat Bolinasbegan increasing by late Jul (Fig. 36), presumablyas a consequenceof post-breedingdispersal from nearby breeding 231 WATERBIRDS AT POINT REYES colonies since there are recoveries in Marin Co. of birds banded at San Francisco Bay. The limitedevidence suggests most post-breedingdispersal is to the north (Gill and Mewaldt1979). The firstfall arrivalsat Limantourand Abbott'sin Aug (Fig. 36) may have been migrants from the north or dispersantsfrom San FranciscoBay breedingcolonies spilling over into lessdesirable habitat. Since 1948 the San FranciscoBay nesting population has increasedfrom about 100 pairsat one site (Sibley1952) to about 2500 pairsat eight major sites (Gill 1977, Rigneyand Rigney 1981). Althoughspring numbers at Bolinashave been relativelyconstant over the years,winter numbers have increasedgreatly (Fig. 14). This parallelsthe increaseof winter numbersin SonomaCo. (G. L. Bolander and Parmeter1978) and the lengthof the northernCalifornia coast from the mid- 1970s (AB 30: 762, AB 31: 369) to the present(AB 42: 316). A flockof 250 Forster'sTerns off Bolinason 31 Dec 1988 (ABN: PP) exemplifiesthis trend and approachesin size high countsduring spring migration (Fig. 36). Forster'sTerns inhabitestuaries, lagoons, inshore waters, freshwater ponds, and marshes. They feed primarilyover mudfiatsin water 1 m or lessdeep (Baltzet al. 1979) but do not catch fish deeper than 30 cm (Salt and Willard 1971). Over the ocean they rangeto 15 km from shore(Briggs et al. 1987). BlackTern (Chlidoniasniger) A very rare fall and spring visitantwith censusrecords of an immatureat Abbott's on 27 Aug and 4 Sep 1980 (ABN) and a breeding-plumagedbird at Bolinason 5 May 1982. Additionalnon-census records are of four singlebirds in fall, extendingthe date spanto 15 Oct, and singleson 14 May 1965 and 30 May 1989 (ABN). In coastalnorthern California Black Terns are rare but regulartran- sientsfrom 23 Apr to 7 Nov, with most recordsin May, Aug, and Sep (ABN); there is also one record for 24 and 25 Jan (AFN 24: 536). The increasingabun- danceof migrantBlack Ternsfrom north to southalong the coastof California (Garrett and Dunn 1981, McCaskie et al. 1979) indicatesthat virtuallyall birds moveto and from interiorbreeding grounds via interiorroutes that intersectthe coast in southern California or farther south. Since at least the 1940s, the Black Tern has decreasedin Californiaboth as a migrant(Garrett and Dunn 1981) and as a breeder(McCaskie et al. 1979). Transientson the northern Californiacoast have been found in estuaries,lagoons, marshes, freshwater ponds, and, occasionally, overthe open oceanup to 16 km from shore(Willett 1933, ABN). CommonMurre (Uria aaige) A very rare fall and winter visitantto the estuarieswith eight singlebirds on eight datesfrom 28 Jul to 3 Oct at Limantourand Bolinasand singlebirds at Bolinason 8 Feb 1973 and 21 Jan 1976. Common Murres breed regularlyat three sitesalong our inshorestudy area, and 17% of California'spopulation breedsnearby on the FarallonIslands (SowIs et al. 1980). Adultsand flightless young dispersefrom these breeding sites between late Jun and mid-Aug (Boekelheide,Ainley, Morrell, Huber, and Lewisin press),shortly before most records of murres in the small estuaries. Most of our estuarine records were of iramaturesthat were likely starved,sick, or injured,as juvenilemortality is very high at that season(Stenzel et al. 1988). Murresalso occur regularly in the mouth of San FranciscoBay in "latesummer" (Grinnell and Wythe 1927) and sometimes in outer TomalesBay. Common Murres primarilyinhabit inshore and offshore watersout to the edge of the continentalshelf, with most birdsconcentrated on the innershelf usually between depths of 55 and 150 m (Wahl 1975, Briggset al. 1987). In the 1970s, the Farallon breedingpopulation recovered dramatically from near extinction due to commercialegging, oil pollution, and disturbance

232 WATERBIRDS AT POINT REYES

(Ainleyand Lewis 1974), only to declinemarkedly again in the 1980s becauseof poor oceanproductivity in El Nifio years,oil pollution,and gill netting(Takekawa et al. in press). Recentdeclines of populationson the centralCalifornia coast, includingall three coloniesalong our inshorestudy area, have been even more dramatic than on the Farallones.

RESULTS AND DISCUSSION

Abundance In all, 122 species,representing 16 familiesof aquaticbirds, were recordedon the wetland censuses. Additional speciesthat have been sightedat other times in the Point Reyesarea (Appendix),but were not detectedon censusesbecause of their extremerarity or their use of non- estuarinehabitats, are not includedin the followinganalyses. Three families-the Anatidae (waterfowl), Scolopacidae (sandpipers and phalaropes),and Laridae(jaegers, gulls, and terns)--accountedfor 68.0% of all specieson censuses. Of the 122 species,7.4% were abundant during at least one season, 11.5% were very common, 21.3% were common,9.0% were fairly common,8.2% were uncommon,and 42.6% were rare to very rare (Table3). Of the 52 very rare or rare species,34 are "very uncommon"or rarer in coastalnorthern California (McCaskie et al. 1979) or "uncommon"or rarer in coastalsouthern California in the comparableseason (Garrett and Dunn 1981), 15 are more numerouson the coastin aquatichabitats poorly representedin the censusedwetlands (Table3), and 3, the SpottedSandpiper, Clapper Rail, and Clark'sGrebe, are difficultto comparefor varyingreasons. The Spotted Sandpiper's solitarybehavior and patchylocal distribution caused us to categorizeit as rare whereasits overallwidespread distribution renders it fairly common on a regional scale (McCaskieet al. 1979, Garrett and Dunn 1981). Likewise,Clapper Rails are more commonat the regionallevel than at Point Reyes becauseof their restrictionto a habitat lacking in our study area. AlthoughClark's and Western grebeswere not differentiatedin regionalaccounts (McCaskie et al. 1979, Garrett and Dunn 1981) or duringour censuses,the availableevidence (see accounts) suggests that these two speciesoccur in the same relativeabundance on Point Reyes as they do alongthe entire Californiacoast.

Seasonal Use Patterns The 70 most numerous species (categories abundant through uncommon),of course,dominate the seasonaluse of the wetlands(Table 3). Although most of these speciesoccur during more than one season, we have categorizedeach by one of six primaryuse patterns:year-round resident (4 species),summer resident (1 species),winter resident (46 species),transient (15 species),and dispersant(4 species). A species-by-speciesanalysis provides some insightinto the importance of the estuariesto springand fall migrants. Of the 15 transient species,six had roughlyequivalent spring and fall peaks,two had almost exclusivelyspring peaks, three had peaksgreater in springthan in fall, and four had peaks greater in fall than in spring. Of the 46 winter resi- 233 WATERBIRDS AT POINT REYES

Table 3 AbundanceRanking for the Season of Peak Occurenceof 122 Speciesof AquaticBirds on WetlandCensuses at Point Reyes

Abundant Common (Continued) Northern Pintail American Avocet AmericanWigeon BlackTurnstone Ruddy Duck Long-billedDowitcher American Coot Red-neckedPhalarope WesternSandpiper HerringGull LeastSandpiper Glaucous-wingedGull Dunlin Caspian Tern Bonaparte'sGull ElegantTern Mew Gull Forster's Tern

VeryCommon FairlyCommon BrownPelican CommonLoon BlackBrant Pied-billedGrebe Green-wingedTeal AmericanWhite Pelican SurfScorer GreatBlue Heron Buffiehead SnowyEgret Black-belliedPlover Black-crownedNight-Heron Willet Red-breastedMerganser MarbledGodwit Whimbrel Sanderling Long-billedCurlew Short-billedDowitcher CommonSnipe Heermann'sGull RedPhalarope Ring-billedGull California Gull Western Gull Uncommon Red-throated Loon Ring-neckedDuck Common Virginia Rail Sora Horned Grebe Eared Grebe Greater Yellowlegs Western Grebe Ruddy Turnstone Red Knot Double-crested Cormorant Baird's Sandpiper Great Egret Mallard PectoralSandpiper Cinnamon Teal Thayer'sGull Northern Shovelar Gadwall Canvasback Rare a Greater Scaup NW Pacific Loon Lesser Scaup Clark's Grebe White-winged Scorer Redhead Common Goldeneye Spotted Sandpiper Snowy Plover Semipalmated Plover Killdeer

234 ß WATERBIRDS AT POINT REYES

Table 3 (Continued)

Very Rare *' Red-necked Grebe * *FW Hooded Merganser OW AshyStorm-Petrel FW CommonMerganser NW Brandt's Cormorant * * Black Rail NW PelagicCormorant ClapperRail * FW American Bittern **FW Common Moorhen ** Little Blue Heron * *UP/FW Sandhill Crane * UP/FW CattleEgret ** LesserGolden-Plover **FW Green-backed Heron SP/FW Black-necked Stilt * * White Ibis FW LesserYellowlegs * FW/UP Tundra Swan RC WanderingTattler * *FW/UP Greater White-fronted * * Bar-tailed Godwit Goose RC Surfbird * *FW/UP Snow Goose * * SemipalmatedSandpiper * 'FW/UP Ross' Goose * * Curlew Sandpiper * * EmperorGoose * * StiltSandpiper * FW/UP Canada Goose ** Ruff **FW Wood Duck SP/FW Wilson'sPhalarope * *FW Blue-wingedTeal NW ParasiticJaeger * * EurasianWigcon * * Franklin'sGull * * Tufted Duck * * Glaucous Gull * * King Eider OW Black-leggedKittiwake * * HarlequinDuck NW Common Tern * * Oldsquaw * * FW BlackTern * * Black Scoter NW Common Murre * * Barrow's Goldeneye a A doubleasterisk indicates the speciesis "very uncommon" or rarerin coastalnorthern California (McCaskieet al. 1979), and "uncommon"or rarerin coastalsouthern California (Garrett and Dunn 1981); a singleasterisk indicates the speciesis relativelyrare in one regionbut not the other.Codes for habitatpreferences that may explain rarity on estuariesor lagoonsbut not on the coast as a whole: FW, freshwater;NW, neritic waters; OW, oceanicwaters; Re, rocky coasts; SP, saltponds; UP, moistuplands.

dents,only 11 had pronouncedpeaks of migrants.Of thesefour had springand fall peaksroughly equivalent, while sevenhad only pronouncedfall peaks. Numbersof the four speciesof dispersantsall peakedin latesummer or fall. Becauseof the tendencyof youngbirds to migrateover broader corridors or to wanderout of rangein fall,inclusion of rarerspecies in thesebreakdowns would bolster the totalnumber of specieswith fall peaks,but thesespecies represent relatively few individuals. Clarificationof the importanceof the wetlandsas springand fall stagingareas awaits detailed analysis of numericalabundance rather than speciestotals for theseseasons. Becausethe dispersantcategory of seasonaluse is not recognizedin most avifaunalworks, the five speciesso classified(including the rarer CattleEgret) deserve further comment. Although these species generally movelong distances between breeding and non-breedingareas they are 235 WATERBIRDS AT POINT REYES not true transientsthat proceedfrom point A to point B duringannual migrations.Instead they generallydisperse northward after breeding, and later retractsouthward, with the distance,timing, duration, and intensity of dispersalvarying greatly (within certain bounds) with fluctuatingfood resources.Cattle Egretsdisperse north into the Point Reyesarea from more southerlybreeding areas between late fall and early winter. The coincidenceof their arrivalwith the initialpart of the rainyseason, rather than the end of their breedingseason, suggests the dispersalis relatedto enhanced food resourcesrather than to post-breedingwanderings. Brown Pelicans,Heermann's Gulls, and ElegantTerns all dispersenorth alongthe Californiacoast from their primarynesting grounds in the Gulf of Californiawith the timing, duration,intensity, and distanceof their movementsapparently fluctuating with food (anchovy)availability in the CaliforniaCurrent (seeSpecies Accounts). In the fall, CaliforniaGulls migrateto the PacificCoast from interiorbreeding sites. They then fan out alongthe coast,but initiallyconcentrate to the north. A patternof progressivelylater peaks of abundanceof CaliforniaGulls with decreasing latitudealong the coastcoincides in timingwith southwardshifts in the abundanceof Brown Pelicans,Heermann's Gulls, and Elegant Terns. This pattern suggeststhat, once on the coast,California Gulls also disperse as a result of a southwardshift in food availability. Although exhibiting other primary seasonaluse patterns, at least part of the Western Gull and Brandt's Cormorant populationsalso dispersesnorth alongthe coastin summerand fall then returnssouth, presumably also in responseto seasonalfluctuations in food supply. The categoryof disper- santsseparates out anothergroup of specieswith commoncharacteristics of seasonaloccurrence, further highlighting the complexitiesof seasonal movements of waterbirds. Most of the 122 speciesfound on our wetlandcensuses do not breed locally. Only 10 speciesbreed regularly in or within 1 km of the wetlands:Pied-billed Grebe, Great Blue Heron, Great Egret, Green-backed Heron, Mallard,Cinnamon Teal, Virginia Rail, AmericanCoot, Snowy Plover,and Killdeer. Eightspecies breed irregularly in or within 1 km of the wetlands:American Bittern, Snowy Egret, Gadwall, Ruddy Duck, and Common Moorhen, definitively,and Blue-wingedTeal, Black Rail, and Sora, probably. Of the 122 speciesan additional19 breed regularly within 75 km, either in San FranciscoBay, on the FarallonIslands, on other coastalrocks and bluffs,or at inland lakes, streams,or marshes: Ashy Storm-Petrel, Double-crestedCormorant, Brandt's Cormorant, PelagicCormorant, Black-crowned Night-Heron, Canada Goose, Wood Duck, Northern Pintail, Northern Shoveler, Common Merganser, ClapperRail, Black-neckedStilt, AmericanAvocet, Spotted Sandpiper, California Gull, Western Gull, Caspian Tern, Forster's Tern, and Common Murre. When we comparedthe primary seasonaluse patternsof the most numerousspecies (abundant through uncommon)within and between taxonomic groups (Table 3), certain trends were evident. All loons (Gaviidae)and grebes(Podicipedidae) were winter residents. Of the 17 speciesof waterfowl(Anatidae), all were primarilywinter residents except 236 WATERBIRDS AT POINT REYES for the Mallard,which is a year-roundresident, and the BlackBrant (for- merlya winterresident), and CinnamonTeal, whichare primarilyspring transients.All rails(Rallidae) were primarilywinter residents. Of the 24 shorebirdspecies (Charadriidae, Recurvirostridae, and Scolopacidae),14 were winter residentsand 10 were transients. The importanceof the Point Reyeswetlands to migrantshorebirds is furtherindicated by the fact that five winter residentsbecame even more numerousin migration. Snowy Plovers,Killdeers, and AmericanAvocets might be classifiedas year-roundresidents but we consideredthem primarilywinter residents becausenumbers on the coast of all three increasedsubstantially in winter. Species of pelicans and cormorants (Pelecanidae and Phalacrocoracidae),herons and egrets(Ardeidae), and gullsand terns (Laridae)were rather widelydistributed among the variousseasonal use categories. These comparisonsstress that Point Reyeswetlands are used pri- marilyby winteringspecies, secondarily by migrants,less by dispersants, and relativelylittle by year-roundresidents, summer residents, and local breeders. About three-quartersof the winter residents,which include loons,grebes, ducks, coots, shorebirds, and gulls,did not havemigratory peakson the estuaries,indicating that the wetlandsserved primarily as a final destinationrather than a stagingarea for migrants. However,at leasta few speciesin mosttaxonomic groups showed peaks of migrants. Althoughshorebirds were the predominantspecies using Point Reyes' wetlandsduring migration periods, the wetlandswere a major staging area for only one speciesof shorebird,the WesternSandpiper in spring. But the importanceof PointReyes estuaries to migrantshorebirds should not be downplayedas Point Reyesis one of only 10 areason the Pacific Coastknown to support20,000 or more shorebirdsduring the peak of migration (Senner and Howe 1984). The Black Brant, which concen- trates in Drake's Estero and TomalesBay during spring migration,is another speciesfor which the Point Reyesestuaries serve as a major stagingarea. Large numbersof loons and scotersappear to use the inshorezone of Drake'sBay as a stagingarea in springand fall. Also, Surf Scotersstage in large numbersin TomalesBay, and furtherwork theremay document the importanceof thatbay to othermigrant species. Most speciesthat occurredprimarily as transientshad peaksin both springand fall, indicatingthat their populationstypically pass along the centralCalifornia coast in both seasons. Althoughspecies richness is highestduring the transitionfrom autumnmigration to the winterperiod we did not determine if overall aquaticbird abundanceparallels this trend. The changethrough the year in the speciescomposition of the wetland communityresulted from the combinationof a large numberof dif- ferentspecies' seasonal use patterns. From late May to late Juneabun- danceand diversitywere at the yearly low. Post-breedinginfluxes of birdsin June and July consistedpredominantly of shorebirds,terns, and dispersantsfrom the Gulf of California;in Augustand Septemberof dabblingducks and shorebirds;and in Octoberand Novemberof divingand dabblingducks, gulls, loons, and grebes. Many of the speciesthat arrived 237 WATERBIRDS AT POINT REYES in October and November continued to increase into December. Most transientshorebirds and ternspassed through by mid-October;some wintering speciescontinued to increasethrough the fall. Gulf of California dispersantsdeclined in October and November. Althoughspring migration beganin late Januarywith the arrivalof CinnamonTeal, in February and Marchthe mostabundant species of winteringwaterfowl, shorebirds, and gulls were still at mid-winter peaks or, particularly in wet years, declining. Numbers of dabblingducks and diving ducks that feed in shallowwater declined rapidly in March,whereas most loons, grebes, and divingducks declined in April. April wasthe peak monthof springshore- bird migration,when the winteringnumbers of somespecies were augmentedby migrantsand other purelytransient species passed through the wetlands;terns were alsomigrating in April. Departureand migration continuedthough most of May until speciesdiversity and population sizesreached summer lows late that month or in earlyJune.

Inter-wetland Variation in Seasonal Occurrence Most instancesof the occurrencepattern of a singlespecies varying among sitesappeared to be explainableby habitat and resourcedifferences. Occurrencepatterns at Abbott'sLagoon frequenfiy differed from thoseat the two estuaries,apparently because of differenthydrographic regimes. BecauseAbbott's is a true lagoon with a barrier bar (see Methods),it becomestidal infrequentlyand irregularlyin winter. Water levelsgenerally rise with the winter rains and declineduring the summer dry period. In contrastto the situationat the estuaries,at Abbott's Lagoon Black-belliedPlovers, Semipalmated Plovers, Killdeer, Marbled Godwits, Sanderlings, Western Sandpipers, Least Sandpipers, and Dunlins(Figs. 23, 25, 27, 28, 29, and 30) remainednumerous for an extendedperiod in fall, were scarceand irregularin winter, and showed at most a limitedpeak in spring. The winter declineof shorebirdsat Abbott'smay havebeen due partlyto the inundationof foragingflats by rising water levels during winter. However, censusesat Abbott's throughoutthe droughtwinter of 1975-76 did not reveal numbersof shorebirdsconsistently higher than in wet years. An alternativeexplana- tion may be that becauseof the lack of tidal influenceand fluctuating winter salinities,Abbott's supports low numbersof prey which are depletedearly in the season,forcing birds to move on. Shorebirdscan depleteprey populationsduring migration (Schneider and Harrington 1981), but it is unknownif prey depletionitself ever causes shorebirds to migrate. Numbersof Sanderlingsat Abbott'sappeared to be more closely linkedto water levelsthan did thoseof other shorebirds.Sanderling numbersthere increased rapidly when new feedingareas were exposed by droppingwater levelswhen stormsopened the lagoonmouth (see account). Funderburkand Springer(1989) also reportedincreased use by shorebirdsof foragingfiats exposed by droppingwater levels at lakes Earl and Talawa.

238 WATERBIRDS AT POINT REYES

Risingwater levelsthat reducedfood auailabilit9seemed to explain both decliningwinter numbersof AmericanWigeon, RuddyDucks, and AmericanCoots at Abbott's(Figs. 17, 22, and 23) and a shift of these species and the Gadwall from freshwater ponds to the estuary at Limantour(Fig. 18). Depletion of food resourcesby the birdsalso may have caused these shifts. Many differencesin occurrencepatterns appeared to be causedby strong preferencesfor one site over another, presumablybecause of grossdifferences in resourcesbetween sites. This probablyexplained why Brown Pelicans,Black-crowned Night-Herons, American Avocets, Common Snipes, and Elegant Terns occurred regularly at Bolinas Lagoonbut irregularlyat Limantourand Abbott's. Apparentlyfor similar reasonsa speciesthat usedtwo or three sitesregularly differed in its seasonaluse of thosesites. For example,Forster's Terns occurredonly as migrantsat Abbott'sand Limantourbut alsowintered at Bolinas(Fig. 36); SemipalmatedPlovers occurred primarily as migrantsat Abbott's and Bolinas but also wintered at Limantour (Fig. 25); Black Turnstones occurredonly as migrantsat Abbott'sbut also winteredat Bolinasand Limantour(Fig. 27); WesternSandpipers staged during spring migration primarilyat Bolinas(Fig. 28). Althoughnot documentedby our census work, peak numbersof loons,grebes, cormorants, diving ducks, and gulls at TomalesBay surelymust have differedin timing from peaks at the other sitesbecause Pacific Herring runs in Tomalesdraw thousandsof birdsthere at irregularintervals in winter. That numbersof loons,grebes, and scotersin summerin inshorewaters (Fig. 5) are higherthan in wetlands(Figs. 4, 8, and 21) alsosuggests resource differences between the areas. In this casebirds may move into lessdesirable areas as their numbers increasein fall and winter and then concentratein preferredareas when numbers decline in summer. The absence of Black-crownedNight-Herons at Limantour and Drake'smay have been due to an absenceof suitabledaytime roosts. It is alsopossible that tradition,or proximityto the largeSan FranciscoBay population,may have playeda role in the occurrenceof a regularpopu- lation of Long-billedCurlews at Bolinas since their main prey items (Stenzel et al. 1976) also occur in abundanceat Limantour, where the curlewoccurred only rarely. Certainspecies were numerousat only one site during the nesting seasonbecause the site offered requisitesfor breedinglacking at other sites. Exampleswere Great Egretsand Great Blue Herons at Bolinas (Fig. 10) and Mallardsand Cinnamon Teal at Abbott's (Figs. 13 and 15). Particularlyearly arrival at one site, for example,of NorthernShovelers at Bolinasor RuddyDucks at Abbott's (Figs.17 and 22), may have reflectedthe earliersettling of birdsat pre- ferredsites, as documentedfor other specieselsewhere (Zwarts 1976, Goss-Custard1977, van der Have et al. 1984). We have no readyexplanations for many differencesin seasonaluse patterns. For example, why was the spring peak of Semipalmated Ploversat Bolinasgreater than the fall peakwhen the reversewas true at both Limantourand Abbott's(Fig.25)? Why did the occurrencepattern of Buffleheadsdiffer at three sites(Fig. 22)? Conversely,did similarpat- 239 WATERBIRDS AT POINT REYES ternsobserved for the samespecies at differentsites really reflect equivalent use? We suspectthat the fall peak of LeastSandpipers at Bolinas may have representedfall stagingor migration,while a similarpeak at Abbott's (Fig. 29) may have reflectedmovement in relation to rising water levelsor prey depletion.

Variationin Timing and Abundance Althoughmany facets of waterbirdmovements seem to be internally regulated,there is a certainamount of fine tuninginfluenced by external factors. In the Point Reyesarea rainfalland winterstorms appeared to be the most important immediatefactors influencing waterbird movements locallyand regionally. Changingwater levelsappeared to cause local shifts of dabblingducks and coots from ponds to the estuaryat Limantour,fall declinesin shorebirdnumbers at Abbott's Lagoon, and dramatic influxesof Sanderlingsto Abbott's. Annual variation in the timing of rainfalland stormsalso appearedto influencethe timing of movements.The arrivalof CommonSnipe at Bolinaswas influenced by the onsetof winter rains. Rainfallalso broadened the spectrumof winter habitat use of shorebirds,such as Black-belliedPlovers, Killdeer, Dunlins, Least Sandpipers,Long-billed Dowitchers, and Marbled Godwits(see accounts),that fed and roostedin rain-soakedpastures, especially at high tides. Rainfallwas also linkedwith rapid declinesof the Northern Pintail, AmericanWigeon, Dunlin, and Long-billedDowitcher at BolinasLagoon (seeaccounts). Pintail departure after intensemid- to late winterrain was a regularphenomenon except in verydry years,while wigeon departure after intenserainfall was lesspredictable. Wigeon may be ableto remain at Bolinaslonger than pintailbecause, unlike other dabbling ducks there, wigeongraze extensively in fieldsand marshes.The infrequentdeparture of the Dunlinand Long-billedDowitcher suggests that thesespecies usually adapt to local floodingand flee only underextreme circumstances. Rainfall and storm tides presumablymay force departureby flooding favoredfeeding areas for extendedperiods. The effectof stormson high tideswas more dramaticat Bolinasthan at Limantourapparently because the former receives more stream inflow for its size and because the estuary mouth faces south toward storm winds and ocean swells. Siltationduring heavy runoff covers feeding areas at creekdeltas, possibly affectingthe dabblingducks that concentratethere. Lack of rainfallmay have triggeredslightly earlier arrival of some speciesin 1976-77, the secondwinter of a two-yeardrought. Althoughour censuseswere infre- quent that year, the Northern Pintail, AmericanWigeon, and American Avocet appeared to arrive slightly earlier, perhaps becauseof the shortageof shallowfreshwater habitat inland. Species that depend the most on irregularly fluctuatingresources variedthe mostin timingof arrival,departure, and peak abundance.The schedulesof Brown Pelicans(Fig. 9), Heermann's Gulls, and Elegant Terns (speciesbreeding primarily in the Gulf of California)varied more than thoseof other regularlyoccurring estuarine species. The timing of 240 WATERBIRDS AT POINT REYES arrivalof thesespecies along the Californiacoast is dependentmostly on when and whether birdsinitiate or fail in their breedingattempts, which is influenced by productivity in the Gulf of California (see Species Accounts). However, oceanicconditions along the California coast can affectthe timingof regionalpeaks because dispersal northward along the coast generally follows the progressionof upwelling in that direction (Andersonand Anderson1976, Briggset al. 1983, Bakun et al. 1974, Brinton 1976). In addition,local resourcefluctuations such as anchovy runs also markedlyaffected seasonal or yearlyvariation in the period of peak abundanceof these same specieson the estuaries(see Species Accounts). As describedin the previoussection, Pacific Herring had a similar influenceon the timing of peak numbersof loons, cormorants, scoters,and gullsin TomalesBay. The irregulartiming and abundanceof Red Phalaropes,Bonaparte's Gulls, and Black-leggedKittiwakes on the estuariesalso appeared to be relatedto fluctuatingresources in the ocean (seeSpecies Accounts). These speciestypically were numerouson the estuariesonly when poor food suppliesor stormscaused them to look for alternativeforaging habitats or shelter. A few speciesincreased or declinedin abundanceduring the study (Fig. 14, SpeciesAccounts). An increasewas apparentin the numberof wintering Marbled Godwits and Gadwallsat Limantour and Bolinas, in the latter speciesparalleling a continent-widetrend (Johnsgard1978, Bellrose 1980). For the Red-breasted Merganser spring numbers increasedat Limantourand Bolinasand winter numbersincreased just at Limantour. Winter numbersof Buffieheadsand Snowy Egretsincreased at Bolinas, as did winter numbers of Black-bellied Plovers, Pied-billed Grebes, and Northern Shovelersat Limantour. Forster's Terns increased in winter and springat Bolinas,the winter increaseparalleling an overall increasein northernCalifornia (see Species Account). Rangeexpansions accountedfor increasesin two species.American Avocets are continuing to expand their range and numbersin northern California. They have occurredregularly on BolinasLagoon since at least1971, andtheir numbersincreased through the 1975-77 drought. They havesince stabilized at somewhatlower levels. Althoughrather rare in the area, the Cattle Egret was first recordedat the time of its initial range expansioninto northern California and now occurs annually on Point Reyes. Populationsof fewer speciesdeclined. Numbersof winteringWillets declinedslightly at Bolinas. Winter numbersof AmericanCoots declined at Bolinasand at Limantour;at Bolinasthe precipitousdecline occurred duringthe secondyear of the 1975-77 drought. The abundancesof some speciesappeared to vary in concert. The yearly variation in abundanceof three fish-eaters,Western/Clark's Grebe, Red-breastedMerganser, and Forster'sTern, closelyparalleled eachother over a 7-yearperiod (Fig. 37), suggestingsimilar resource use. During the two droughtwinters we recordedhigh numbersof most species of dabbling ducks, American Coots, American Avocets, and Dunlin,which were followedby much lower numbersin 1977-78 (Fig. 14), when rainfallreturned to normal levels. Presumablythese species concentratedon estuarieswhen freshwaterhabitats inland dried up. 241 WATERBIRDS AT POINT REYES

In recent years intensive census studies (e.g., Prater 1981) and especially ecological studies of single species (e.g., Evans 1984, Pienkowskiand Evans1984) have expandedour understandingsof the complexitiesof seasonalmovements. Seasonaloccurrence patterns respondto, and compromisewith, constraintsplaced upon speciesin their efforts to breed, molt, migrate, and maintain themselvesover winter. To meet differentseasonal demands waterbirds frequently move great distances.Although generally these movements are betweensum- mering and winteringareas, there are also many within-seasonmove- ments. Shorebirdsmay usea numberof areaswithin a generalwintering range. For example,some birds may migrateto one area in fall to molt

3O ß

ß IO

m•

ira,

67 68 69 70 71 72 73 74 75 76 77 78 79 8081

Figure37. Winternumbers of threespecies of fish-eatingbirds at BolinasLagoon between 1972-73 and 1981-82. Dotted line, Western/Clark's Grebe; dashed line, Red-breastedMerganser; solid line, Forster'sTern. 242 WATERBIRDS AT POINT REYES

("molt migration"),to another to "overwinter,"and to yet another for springmolt beforecommencing long-distance migration to their breeding grounds(Pienkowski and Evans1984). "Oversummering"shorebirds also move unknown directions for unknown durations (Loftin 1962). Waterfowl undertakeshort-distance molt migrations,post-breeding dispersal,and sometimesnorthward movements in fall duringunseasonally mild weather (Hochbaum 1955). Strategiesused in one season may have far-reachingeffects in another. For example,in shorebirdsthe dis- tancea speciesmigrates or the degreeof sexualsegregation on the win- teringgrounds may be linkedto the matingsystem (Myers 1981a,b). Within species,layers of complexityin seasonaluse patternsare (1) differencesin migrationroutes and timing in differentpopulations (e.g., see Harringtonand Morrison1979); (2) differentschedules of migration by age and sex classes(see Page et al. 1979, Morrison 1984); (3) geographic or habitat segregationof sex or age classeson the wintering grounds(e.g., Bellroseet al. 1961, Page et al. 1972, Alexander 1983, Jorde et al. 1984); and (4) differentseasonal use strategiesof individuals (e.g., Evansand Pienkowski1982, Townshend1985). Many of these complexities follow predictable patterns within taxonomic groups. Althoughthere are exceptions,in shorebirdsthe timing of migrationof the sexestypically differs in spring (e.g., Myers 1981b) and fall (e.g., Morrison1984). In fall adultsmigrate before juveniles (e.g., Page et al. I979). Fall migrationis slowerthan springmigration (e.g., Pienkowski and Evans1984, Jehl 1979), and the fall migratorypathways of juveniles are broaderthan those of adults(e.g., Jehl 1979). Within a taxonomic group,there is, of course,some variation in seasonaluse strategy such as the short- or long-hopmigrations of shorebirds(e.g., Pienkowskiand Evans 1984). Trends in seasonaluse patterns may crosstaxonomic boundaries. Both shorebirdsand waterfowl "oversummering"on the wintering grounds are usually immature (Bellrose 1980, Johnsgard 1981). Despitethe vast improvementin knowledgeof the detailsof seasonal movements,the reasonsfor concentrationsof particularspecies on particular estuariesat particular times of year are poorly known (Evans 1984). Much of the recent work on winter ecologyof waterbirdshas focusedon energeticsand how birds stay alive. However, changesin species'use of an area have seldombeen shownto relateto the density of availableprey or changesin daylightor averagewinter temperatures, any of which mightbe expectedto make a differencein a bird'sability to maintainitself. This lack of correlationsuggests that many environmental factorsmay not be the proximatecauses of movementswithin the non- breedingrange (Evans1976, Evansand Dugan 1984). Althoughhard weather inducessome movementsin winter, apparentlymost estuarine shorebirdsattempt to endure,not flee, periodsof adverseweather (Evans 1976); hard-weathermovements appear more frequentin inlandspecies of shorebirds(Pienkowski et al. 1984). Some patterns of change in winter numbersmay depend upon movementsfrom outsidethe local system, some on the social behavior of birds on an estuary (see Townshend1985). Most studies,however, have been conductedat latio 243 WATERBIRDS AT POINT REYES tudeswhere freezingtemperatures are thoughtto be the primary factor increasingenergy demands while decreasingprey activityand availability (e.g., Evansand Dugan 1984, Pienkowskiet al. 1984). In someclimates rainfall actingvia water levelscan causemovements of waterbirdsthat rely on ephemeralfreshwater habitats (e.g., Kushlan1981). Our census studieson Point Reyeswetlands suggested that, in a seasonallywet envi- ronment, rainfalland stormsalso caused waterbirds to move. Muchremains to be learnedabout the patternsand causesof seasonal waterbirdmovements, which will be understoodonly throughthe coordi- nation of censusefforts with studiesof individualspecies, particularly those involvingmarked birds. Censusstudies alone have many inherent limitations since our perceptions of seasonal abundance patterns obtainedfrom graphsmay not be correct. For example,a springdecline of Sanderlingsat BodegaBay easilymight have been interpretedas the beginningof springmigration, but sightingsof bandedbirds revealed that the declinereflected local movementsto Point Reyes(Myers et al. 1985). Also, stablemid-winter peaks may suggesta lack of movementwhen in fact they conceala dynamicstability in which departuresand arrivals roughlycancel each other out (Evansand Pienkowski1982, Myerset al. 1985). For speciesthat occur year round, migration timing may be demonstratedonly by intensivebanding studies (e.g., Warriner et al. 1986). The importance of broad regional work is illustratedby both intra-estuarine(e.g., Bayer 1983) and inter-estuarinevariation in seasonal abundancepatterns (e.g., Jurek 1972, 1974; Prater 1979; this study).

CaliforniaPerspective The diversityof birds'seasonal use strategies in an estuaryor a region is determinedby climate,habitat and resourcediversity, geographic set- ting, and perhapstradition. The Mediterraneanclimate, which character- izesmuch of California,is foundnowhere else in North Americaand only in a few placesin the world (Major 1977). This climateis winter wet and summerdry, with the vast majorityof precipitationfalling as rain from October throughApril. We have discussedexamples of the effectsof seasonalrainfall on birdsin the Point Reyeswetlands. We suspectthat the amount of rainfall influences movement between estuarine and interior freshwaterhabitats, particularlyin extremely wet and dry years. Such movementshave been mentionedin the literatureonly infrequently (as for the Canvasback,Rienecker 1985), althoughwe suspectthey are an integral part of many species'strategies. Temperaturesalong the California coast vary little between summerand winter, with few days below freezing annually; generallytemperatures decrease and rainfall increaseswith latitudealong the coast. The mild winter climate allowsa highdiversity of waterbirdsto overwinteron the coast. Generalavifaunal works (Grinnell and Miller 1944, McCaskie et al. 1979, Garrett and Dunn 1981) showthat coastalCalifornia is primarilya winteringarea for estuarinewaterbirds, as demonstratedalso by our studyat Point Reyes. California is at the northern end of a broad geographicalarea (from 40øN to 40øS) with high numbersof shorebirdspecies in the northern

244 WATERBIRDS AT POINT REYES winter (Pitelka1979b). We know of no similaranalysis for waterfowlor otherwaterbirds but suspectthat California,and particularlyPoint Reyes, is at the high end of speciesdiversity for estuarinewaterbirds in winter on the PacificCoast and perhapsfor all of North America. The productive current off the coast of California, Oregon, and Washingtonundergoes unique seasonal cycles not found elsewherein North America. The influenceof thesecycles on seabirdsbreeding on the Farallon Islands and on the seasonal occurrence of offshore and pelagicspecies off the Californiacoast has been well described(Ainley 1976a, Briggset al. 1987, Ainley and Boekelheidein press). Research has alsobegun to focuson the effectsof these cycleson estuarineand inshore speciessuch as the Brown Pelican (Anderson and Anderson 1976, Briggset al. 1981, 1983) and the Western Gull (Spear 1988). We surmisethat severalspecies that feed in late summer and fall in both inshoreand estuarinewaters have seasonalabundance patterns affected by the cycleof upwelling,which begins progressively later in the spring and summerfrom southto north alongthe Californiacoast (Bakun et al. 1974, Brinton 1976). In addition to the Brown Pelican and Western Gull, these speciesare Brandt'sCormorant, Heermann'sGull, California Gull, and ElegantTern (seeSpecies Accounts). The high diversityof specieswintering in the Point Reyesarea and Californiain generalmust reflect to somedegree a highdiversity of habitats. The extent,and presumablydiversity, of coastalwetland habitats on the West Coast and their importance to waterfowl, however, are much less than on the Gulf and Atlantic coasts (Shaw and Fredine 1971, Sanderson1980). On the basisof fragmentaryinformation, the East Coast appears to be more important, overall, than the West Coast for stagingof migratoryshorebirds, but the latterarea and the coastalsouth- easternUnited States are the onlymajor wintering areas for shorebirdsin North America(Senner and Howe 1984). Althoughthe limitedextent of West Coast estuariesprobably is responsiblefor their secondaryimportance as staginggrounds, geography must also play a part. California's position on the western edge of North America and the northwest-to- southeastorientation of the Americasplaces it out of a direct line for speciesmigrating from the Arctic to tropicaland southtemperate areas, where most WesternHemisphere shorebirds winter (Sennerand Howe 1984). On a regional scale, even when speciesare moving along a roughlystraight corridor, migratory stops may by-passseemingly suitable feedingareas because they are not strategicallyplaced in relationto a direct route or the length of a particularmigratory flight (e.g., Wilson 1981). An underlyingtheme in recent researchon waterbirds,because of many species'long-distance movements and elaboratelife-history strategies, is the importanceof advancingknowledge applicable to conserva- tion on a broad geographicscale (e.g., Pitelka 1979a, Prater 1981, Senner and Howe 1984). Much of this work has focused on single speciesor specifictaxonomic groups, particularly waterfowl and shorebirds, and only exceptionallyhave coordinatedefforts been made to censusall estuarinespecies in a large geographicarea (e.g., Prater 245 WATERBIRDS AT POINT REYES

1981). Advancementof knowledgehas been unevengeographically, with Europeleading the way (e.g., Prater 1981, Evanset al. 1984), followed more recentlyby coordinatedshorebird studies on the east and west coasts of North America and in Central and South America (Morrison and Harrington 1979, Myers 1983, Stenzel et al. 1989). Althoughsome attentionhas been focusedon the PacificCoast (Pitelka 1979a), there has been no region-wideeffort to censuswaterbirds except for federaland statewaterfowl surveys and shorebirdstudies in California (Jurek1974, Stenzelet al. 1989). Becauseof its uniqueclimate, its role as a wintering area for aquatic birds, and the different sourcesof its waterbirdpopulations, the PacificCoast can providea valuableperspec- tive on waterbirds' seasonaloccurrence patterns. Broad-scalecensus work is neededto provideinformation on the importanceof variouswet- landsto waterbirds,while species-specificstudies are neededfor knowl- edgeabout local movements, habitat requirements, and foragingecology. Intensivelong-term local censusstudies such as ours are most usefulin documentinglong-term populationtrends, year-to-yearvariation in seasonaloccurrence patterns, and, perhapsmost importantly,in uncovering patternsthat cry out for focusedresearch.

SUMMARY

Long-term censusesat Point Reyes in coastal California provided informationon the seasonalabundance of 122 speciesof aquaticbirds. Two-thirdsof the specieswere membersof three families--theAnatidae (waterfowl), Scolopacidae(sandpipers and phalaropes), and Laridae (jaegers,gulls, and terns). The Point Reyeswetlands were usedprimarily by winter residents,secondarily by migrants,less by dispersants,and relativelylittle by year-roundresidents, summer residents, and breeders.The importanceof Point Reyesas a winteringarea was furtheremphasized by the fact that about 75% of the winteringspecies did not have migratory peakson the wetlands.Shorebirds were the predominantgroup showing migratorypeaks. Althoughmost migrant species occurred in both spring and fall, the numberof speciesof waterbirdswas greatestin fall and early winter. Inter-wetlandvariation in seasonaloccurrence patterns was usually explainableby habitatand resourcedifferences. The contrastsbetween a lagoonand two estuarieswere due to differenthydrographic regimes that may have causedchanges in seasonalfood availabilityor loweredprey densities,resulting in birdsleaving after they depletedtheir prey. Rainfall and stormswere probablythe most importantproximate factors influ- encinglocal and regionalhabitat shiftsai•d the timing of these movements. The highestnumbers of many speciesthat usefresh water were found on the coastal wetlandsduring two years of a major drought. California'sseasonal ocean cyclesalso affectedsome wetlandspecies. Thesespecies varied the mostin timingof arrival,departure, and peak abundance,and most dispersednorth after breeding in the Gulf of California,with their movementstimed to food availabilityand the progressionof upwellingin springand summerfrom southto north along 246 WATERBIRDS AT POINT REYES the coast. Populationfluctuations and localmovements of Northern Anchoviesand PacificHerring also stronglyaffected the timing and abundanceof somefish- and egg-eaters. On a continentalscale, wetlands along the centralCalifornia coast appearto be on the highend of winteringwaterbird diversity, but overall theyare of secondaryimportance as areasfor winteringwaterfowl and stagingmigrant shorebirds. Much work on the complexitiesof seasonal movementshas been conducted in north temperateareas where freezing temperatureslimit numbersof winteringspecies. Because of its seasonallywet climate,its importanceas a winteringarea, and the different sourcesof its waterbirdpopulations, California can providea valuable additionalperspective on seasonalwaterbird movements that mayfurther helpconservation efforts.

ACKNOWLEDGMENTS

Many volunteersand staff of Point ReyesBird Observatoryhelped with the censusesthat made this paper possible. We cannot list all their nameshere but expressour deepest thanks to all who helped. Bill Clow, Bill Eastman, Phil Henderson, Phil Lenna, Mary Mayer, Libby Meyers, Bev Mcintosh, Helen Pratt, John Smail, Bob Stewart, Alice Williams, and Pain Williamswere regular cen- susersfor extendedperiods during the study. Howard Cogswelltook aerial pho- tographsused for calculatinghabitat areas of the estuaries.Christmas Bird Count summarieswere kindlyprovided for the Point ReyesPeninsula count by Gary Fellers,Bill Lenarz, and Irene Timossi, and for the Marin Co. (southern)count by DianneSierra. The CaliforniaDepartment of Fishand Game kindly shared census data for Black Brant, J.P. Myers and associatesfor Sanderlings,and Larry B. Spear for CaliforniaGulls. David F. DeSanteand GeoffreyR. Geupelgladly shared rainfall data collected at PRBO's Palomarin Field Station. Stephen F. Bailey,Alan D. Barron,Kurt E Campbell,Richard A. Erickson,Ron LeValley,and David G. Yee kindly providedinformation from the notebooksof the Middle PacificCoast Region of American Bira•s,as did Don Robersonfrom the data base of the California Bird RecordsCommittee. We thank Chris Cutler, Julia Gennert, Karen Hamilton,and SusanTrivelpiece for draftingmany of the figures,Gary Fellersfor providingaccess to a letteringmachine for preparingfigures, and Susan Goldhaber,Meg Sanders,Meg Simonds,Liz Tuomi, and O'Brien Youngfor their effortsin preparationof the manuscript. Peter G. Connorsand JosephMorlan providedmany helpfulcomments and criticismsof the manuscript,and Laurence C. Binfordthoughtfully reviewed an earlierdraft. JosephMorlan also reviewed the Appendixdrafted after the initialreviews. Several persons provided helpful insight on particularspecies: Daniel W. Anderson(Brown Pelican,Heermann's Gull, and Elegant Tern), Harry R. Carter (breeding seabirds),David B. Lewis (Brown Pelican),Helen M. Pratt (heronsand egrets),Fred C. Schaffner(Elegant Tern), and LarryB. Spear(Western Gull). Financialsupport for someof the censusingcame throughContract DE-AC03-79EV10254 from the U.S. Departmentof Energy. A grantfrom the Marin SanctuaryProgram Office of NOAA helpedfund the preparationof the report from whichthis paper evolved. Long-termprojects such as thiswould not be possiblewithout the supportof the PRBO generalmembership. This is ContributionNo. 344 of Point ReyesBird Observatory.

247 WATERBIRDS AT POINT REYES

LITERATURE CITED

Ainley,D. G. 1976a. The occurrenceof seabirdsin the coastalregion of California.W. Birds 7: 33-68. Ainley,D. G. 1976b. A spectacularseabird dieoff in 1976: A beachsurvey report. Point ReyesBird Ohs. Newsl.39. Ainley,D. G., Anderson,D. W., and Kelly,P.R. 1981. Feedingecology of marine.cormorants in southwestern North America. Condor 83: 120-131. Ainley, D. G., and Boekelheide,R. J., eds. In press. Seabirdsof the FarallonIslands: Ecology,Dynamics, and Structure of an Upwelling-SystemCommunity. Stanford Univ. Press,Stanford. Ainley,D. G., andLewis, T. J. 1974. The historyof FarallonIsland marine bird populations, 1854-1972. Condor 76: 432-446. Ainley, D. G., and Sanger,G.A. 1979. Trophicrelations of seabirdsin the northeastern Pacific Ocean and Bering Sea, in Conservationof marine birds of northern North America(J. C. Bartonekand D. N. Nettleship,eds.), pp. 95-122. U.S. FishWildl. Serv. Wildl. Res. Rept. 11. Alexander,W. C. 1983. Differentialsex distributionsof winteringdiving ducks (Aythyini) in North America. Am. Birds 37: 26-29. AmericanOrnithologists' Union. 1957. Check-listof North AmericanBirds. 5th ed. Am. Ornithol. Union, Baltimore. AmericanOrnithologists' Union. 1983. Check-listof North AmericanBirds. 6th ed. Am. Ornithol. Union, Lawrence, KS. Anderson,D. W., and Anderson,I.T. 1976. Distributionand statusof Brown Pelicansin the California current. Am. Birds 30: 3-12. Anderson,D. W., and Gress,F. 1983. Statusof a northernpopulation of CaliforniaBrown Pelicans. Condor 85: 79-88. Arnold,K.A. 1981. Fidelityof CommonSnipe to wintergrounds, with commentson local movements. Southwest. Nat. 26: 319-321. Bakun,A., McClain,D. R., and Mayo, E V. 1974. The meanannual upwelling off western North America as observedfrom surfacemeasurements. Fish Bull., U.S. 72: 843-844. Baltz, D. M., Morejohn,G. V., and Antrim, B. S. 1979. Size-selectivepredation and food habits of two California terns. W. Birds 10: 17-24. Bayer, R. D. 1983. Seasonaloccurrences of ten waterbirdspecies at YaquinaEstuary, Oregon. Murrelet64: 78-86. Bellrose,F. C. 1980. Ducks, Geese, and Swansof North America. 3rd ed. Stackpole, Harrisburg,PA. Bellrose,E C., Scott,T. G., Hawkins,A. S., and Low, J. B. 1961. Sex ratiosand age ratios in North American ducks. I11.Nat. Hist. Surv. Bull. 27: 391-474. Bent, A. C. 1921. Life historiesof North Americangulls and terns. U.S. Natl. Mus. Bull. 113. Bent, A. C. 1926. Life historiesof North American marshbirds. U.S. Natl. Mus. Bull. 135. Bergquist,J.R. 1978. Depositionalhistory and fault-relatedstudies, Bolinas Lagoon, California. Open-FileRept. 78-802, U. S. Geol. Surv.,Menlo Park. Binford,L.C. 1983. Sixth report of the CaliforniaBird RecordsCommittee. W. Birds 14: 127-145. Binford, L. C. 1985. Seventhreport of the CaliforniaBird RecordsCommittee. W. Birds 16:29-48 Blick, D. J., Jr. 1980. Advantagesof flockingin somewintering shorebirds. Ph.D. thesis, Univ. of Michigan,Ann Arbor.

248 WATERBIRDS AT POINT REYES

Boekelheide, R. J., Ainley, D. G., Huber, H. R., and Lewis, T. J. In press. Pelagic Cormorantand Double-crestedCormorant, in Seabirdsof the FarallonIslands: Ecology, Dynamics,and Structurein an Upwelling-SystemCommunity (D. G. Ainley and R. J. Boekelheide,eds.). StanfordUniv. Press,Stanford. Boekelheide,R. J., Ainley, D. G., Morrell, S. H., Huber, H. R., and Lewis,T. J. In press. CommonMurre, in Seabirdsof the FarallonIslands: Ecology, Dynamics, and Structureof an Upwelling-SystemCommunity (D. G. Ainley and R. J. Boekelheide,eds.). Stanford Univ. Press,Stanford. Boekelheide,R. J., Ainley, D. G., Morrell, S. H., and Lewis, T. J. In press. Brandt's Cormorant,in Seabirdsof the FarallonIslands: Ecology, Dynamics, and Structurein an Upwelling-SystemCommunity (D. G. Ainley and R. J. Boekelheide,eds.). StanfordUniv. Press,Stanford. Bolander,G. L., and Parmeter, B.D. 1978. Birds of Sonoma County, California: An AnnotatedChecklist and BirdingGazetteer. B. D. Parmeter,2500 EmersonSt., Napa, CA 94558. Bolander,L. P., Jr., and Bryant,C.A. 1930. Some noteson Point Reyesbirds. Condor32: 70-72. Bollman,E H., Thelin, P. K., and Forester,R. T. 1970. Bimonthlybird countsat selected observationpoints around San FranciscoBay, February,1964, to January,1966. Calif. Fish Game 56: 224-239. Brewster,W. 1907. Notes on the Black Rail of California. Auk 24: 205-210. Briggs,K. T., Dettman,K. T., Lewis,D. B., and Tyler,W.B. 1984. Phalaropefeeding in relationto autumnupwelling off California,in Marinebirds: Their feedingecology and commercialfisheries relationships (D. N. Nettleship,G. A. Sanger,and P. F. Springer, eds.),pp. 51-62. Proc. Pac. SeabirdGroup Symp., Seattle,6-8 Jan 1982. Briggs, K. T., Lewis, D. B., Tyler, W. B., and Hunt, G. L., Jr. 1981. Brown Pelicansin southern California: Habitat use and environmental fluctuations. Condor 83: 1-15. Briggs,K. T., Tyler, W. B., Lewis, D.' B., and Carlson,D. R. 1987. Bird communitiesat sea off California: 1975 to 1983. Studies Avian Biol. 11. Briggs,K. T., Tyler,W. B., Lewis,D. B., Kelly, P. R., and Croll, D.A. 1983. Brown Pelicans in central and northern California. J. Field Ornithol. 54: 353-373. Brinton,E. 1976. Populationbiology of Euphausiapacifica off southernCalifornia. U.S. Fish Wild. Serv. Fish. Bull. 74: 733-762. Carter,H. R., and Erickson,R.A. 1988. Populationstatus and conservationproblems of the MarbledMurrelet in California,1897-1987. Finalreport to Calif. Dept. FishGame, con- tract FG7569 (FY 1987-88). Caspers, H. 1967. Estuaries:Analysis of definitionsand biologicalconsiderations, in Estuaries(G. H. Lauff,ed.), pp. 6-8. Am. Assoc.Adv. Sci. Publ.83. Chaniot,G. E., Jr. 1966. AnotherCalifornia specimen of Pluvialisdorninica fulva. Condor 68: 212. Cogswell,H. L. 1974. Ecologicalfactors in the hazardof gullsto aircraftin a baysidecom- plex of airportsand solidwaste sites, in Proc. Conf. on Biol. Aspectsof the Bird/Aircraft CollisionProblem, pp. 27-108. ClemsonUniv., Clemson,SC. Cogswell,H.L. 1977. Waterbirdsof California.Univ. Calif.Press, Berkeley. Connelly,J., Jr. 1978. Trendsin Blue-wingedand CinnamonTeal populationsin eastern Washington.Murrelet 59: 2-6. Connelly,J. W., and Ball, I.J. 1984. Comparisonsof aspectsof breedingBlue-winged and CinnamonTeal in easternWashington. Wilson Bull. 96: 626-633. Connors,P. G. 1983. Taxonomy,distribution, and evolutionof Golden Plovers(Pluvialis dorninicaand Pluvialisfulva). Auk 100: 607-620. Connors,P. G., Myers,J.P., Connors,C. S. W., and Pitelka,E A. 1981. Interhabitatmove- ments by Sanderlingsin relationto foragingprofitability and the tidal cycle. Auk 98: 49-64.

249 WATERBIRDS AT POINT REYES

Connors,P. G., Myers,J.P., and Pitelka,F.A. 1979. Seasonalhabitat use by arcticAlaskan shorebirds,in Shorebirdsin marine environments(F. A. Pitelka, ed.), pp. 101-111. Studies Avian Biol. 2. Connors,P. G., and Smith,K. G. 1982. Oceanplastic particle pollution: Suspected effect on fat depositionin RedPhalaropes. Marine Pollution Bull. 13: 18-20. Conover,M.R. 1983. Recentchanges in Ring-billedand CaliforniaGull populationsin the western United States. Wilson Bull. 95: 362-383. Cottam, C., Lynch,J. J., and Nelson,A. L. 1944: Food habitsand managementof Americansea brant. J. Wildl.Mgmt. 8: 36-56. Coulson,J. C. 1966. The movementsof the Ki•tiwake.Bird Study 13: 107-115. Coulter,M. 1975. Post-breedingmovements and mortalityin the WesternGull, Larus occidentalis. Condor 77: 243-249. Crosby,G. T. 1972. Spreadof the CattleEgret in the westernhemisphere. Bird-Banding 43: 205-211. DeSante,D. F., and Ainley, D. G. 1980. The avifaunaof the SouthFarallon Islands, California. Studies Avian Biol. 4. Devillers,P., McCaskie,G., and Jehl, J. R., Jr. 1971. The distributionof certainlarge gulls (Larus)in southernCalifornia and BajaCalifornia. Calif. Birds2: 11-26. Dunn, J. L. 1988. Tenthreport of the CaliforniaBird RecordsCommittee. W. Birds 19: 129-163. Einarson,A.S. 1965. Black Brant, Sea Gooseof the PacificCoast. Univ. Wash. Press, Seattle. Erskine,A. J. 1972. Buffieheads.Can. Wildl.Serv. Monogr. Set. 4. Evans,P. R. 1976. Energybalance and optimalforaging strategies in shorebirds:Some implicationsfor their distributionand movementin the non-breedingseason. Ardea 64: 117-139. Evans,P. R. 1984. The significanceof specificareas on the Palaearctic-Africanmigration routesof waders:The Britishhies, in CoastalWaders and Wildfowl in Winter (P. R. Evans, J. D. Goss-Custard,and W. G. Hale, eds.), pp. 261-275. CambridgeUniv. Press, Cambridge. Evans,P. R., andDugan, P.J. 1984. Coastalbirds: Numbers in relationto foodresources, in CoastalWaders and Wildfowlin Winter (P. R. Evans,J. D. Goss-Custard,and W. G. Hale, eds.),pp. 8-28. CambridgeUniv. Press,Cambridge. Evans,P. R., Goss-Custard,J. D., and Hale, W. G., eds. 1984. CoastalWaders and Wildfowl in Winter. CambridgeUniv. Press,Cambridge. Evans, P. R., and Pienkowski,M.W. 1982. Behaviorof shelducksTadorna tadorna in a w/nterflock: Does regulation occur? J. Anita. Ecol.51: 241-262. Evens,J., and Page,G. 1983. The ecologyof rail populationsat Corte MaderaEcological Reserve:With recommendationsfor management. Point ReyesBird Obs./Marin AudubonSoc. Mgmt. Rept. P.R.B.O., 4990 Shoreline Hwy., Stinson Beach, CA 94970. Evens,J., and Page, G. 1984. California Clapper Rail Railus Iongirostrlsobsoletus. EndangeredSpecies Information System. U.S. FishWildl. Serv., Portland, OR. Evens,J., andPage, G.W. 1986. Predationon BlackRails during high tides in saltmarshes. Condor 88.' 107-109. Evens,J. G., Page G. W., Stenzel,L. E., Stallcup,R. W., and Henderson,P. H. 1989. Distributionand relativeabundance of the CaliforniaBlack Rail (Laterallusjarnaicensis coturniculus)in the tidal marshesof the San FranciscoBay estuary. Reportto Calif. Dept. FishGame, Sacramento. Evens,J., and Stallcup,R. 1986a. Monitoringavain coremunites at Olema and Livermore marshes,Tomales Bay, California:November 1985 to March 1986. Reportto Audubon CanyonRanch, 4900 ShorelineHwy., StinsonBeach, CA 94970.

250 WATERBIRDS AT POINT REYES

Evens,J., and Stallcup,R. 1986b. The 1986 breedingseason at Olema and Livermore marshes,Tomales Bay, California:A monitoringproject by AudubonCanyon Ranch, 4900 ShorelineHwy., StinsonBeach, CA 94970. Funderburk,S. L., and Springer,P. F. 1989. Wetlandbird seasonal abundance and habitat use at Lake Earl and Lake Talawa, California. Calif. Fish Game 75: 85-101. Gaines,D. 1988. Birdsof Yosemiteand the EastSlope. ArtemisiaPress, Lee Vining, CA. Garrett K., and Dunn, J. 1981. Birdsof SouthernCalifornia. Los AngelesAudubon Soc., Los Angeles. Gerdes,G. L. 1970. Water bird countsat Morro Bay, 1966-67. Wildl. Mgmt. Branch Admin.Rept. 70-8. Calif. Dept. FishGame, Sacramento. Gerstenberg, R. H. 1972. A study of shorebirds (Charadrii) in Humboldt Bay, California--1968 to 1969. M.S. thesis,Humboldt State Univ., Arcata. Gill, R., Jr. 1972a. Reviewof the bi-monthlybird countsof San FranciscoBay, February 1964-December 1965. Wildl. Mgmt. Branch Admin. Rept. 72-8. Calif. Dept. Fish Game, Sacramento. Gill, R., Jr. 1972b. South San FranciscoBay breedingbird survey,1971. Wildi. Mgmt. BranchAdmin. Rept. 72-6. Calif. Dept. FishGame, Sacramento. Gill, R., Jr. 1976. On the foragingdistance and prey selectionof nestingCaspian Terns. Calif. Fish Game 62: 155. Gill, R., Jr. 1977. Breedingavifauna of the southSan FranciscoBay estuary. W. Birds8: 1-12. Gill, R., Jr. 1979. Statusand distributionof the CaliforniaClapper Rail (Railus Iongirostris obsoletus). Calif. FishGame 65: 36-49. Gill, R., Jr., and Mewaidt,L. R. 1979. Dispersaland migratorypatterns of San Francisco Bay-producedherons, egrets, and terns. N. Am. Bird Bander4: 4-13. Gill, R. E., Jr., and Mewaldt,L. R. 1983. Pacificcoast Caspian Terns: Dynamics of an expandingpopulation. Auk 100: 369-381. Goss-Custard,J. D. 1977. The ecologyof the Wash. Iii. Density-relatedbehavior and the possibleeffects of lossof feedinggrounds on wadingbirds (Charadrii). J. Appl. Ecol. 14: 721-739. Gress,F., Risebrough,R. W., Anderson,D. W., Kill, L. E, and Jehl, J. R., Jr. 1973. Reproductivefailure of Double-crestedCormorants in southernCalifornia and Baja California. WilsonBull. 85: 197-208. Grinnell,J., Bryant,H. C., and Storer,T. I. 1918. The Game Birdsof California. Univ. Calif. Press,Berkeley. Grinnell,J., and Miller,A. H. 1944. The distributionof the birdsof California. Pac. Coast Avifauna 27. Grinnell,J., and Wythe, M. W. 1927. Directoryto the bird life of the San FranciscoBay region. Pac. CoastAvifauna 18. The Gull. Golden Gate AudubonSociety monthly bulletin. G.G.A.S., 1250 AddisonSt., #107B, Berkeley,CA 94702. Harfington,B. A. 1975. Pelagicgulls in winter off southernCalifornia. Condor 77: 346-350. Harrington,B.A. 1982. Untyingthe enigmaof the Red Knot. LivingBird Quart. 1(2):4-7. Harrington,B. A., and Morrison,R. I. G. 1979. SemipalmatedSandpiper migration in North America, in Shorebirdsin marine environments(E A. Pitelka, ed.), pp. 83-100. Studies Avian Biol. 2. Henderson,P. 1979. A Dotterel on SoutheastFarallon Island,California. W. Birds 10: 92-94. Henny, C., and Collins,J. 1980. Early concentrationsof Brown Pelicansalong southern Oregoncoast. Murrelet61: 99-100.

251 WATERBIRDS AT POINT REYES

Hochbaum, H. A. 1955. Travels and Traditions of Waterfowl. Univ. Minn. Press, Minneapolis. Hoffman, W., Wiens, J. A., and Scott, J. M. 1978. Hybridizationbetween gulls (Larus glaucescensand L. occidentalis)in the Pacificnorthwest. Auk 95: 441-458. Holmes, R.T. 1966. Breedingecology and annualcycle adaptations of the Red-backed Sandpiper(Calidris alpina) in northernAlaska. Condor68: 3-46. Ives,J. H. 1972. CommonEgret and GreatBlue Heron neststudy, Indian Island, Humboldt County,California 1971-72. WildeMgmt. BranchAdmin. Rept. No. 72-9. Calif. Dept. Fish Game, Sacramento. Ivey, G. L., Stern, M. A., and Carey, C.G. 1988. An increasingWhite-faced Ibis population in Oregon. W. Birds19: 105-108. Jehl, J. R., Jr. 1963. An investigationof fall-migratingdowitchers in New Jersey. Wilson Bull. 75: 250-261. Jehl, J. R., Jr. 1979. The autumnmigration of Baird'sSandpiper, in Shorebirdsin marine environments(E A. Pitelka,ed.), pp. 55-68. StudiesAvian Biol. 2. Jehl,J. R., Jr. 1988. Biologyof the FaredGrebe and Wilson's Phalarope in the nonbreeding season:A studyof adaptationsto salinelakes. StudiesAvian Biol. 12. Jehl, J. R., Jr., and Craig, A.M. 1970. San Diego shorebirdstudy. Spec. Wildl. Invest. Rept., ProjectW-54-R. Calif.Dept. FishGame, Sacramento. Jeter,H. H., and Paxton,R.O. 1964. LittleBlue Heron collectedin California.Condor 66: 447. Johnsgard,P.A. 1978. Ducks,Geese, and Swansof the World. Univ. Nebr.Press, Lincoln. Johnsgard,P.A. 1981. The Plovers,Sandpipers, and Snipesof the World. Univ. Nebr. Press,Lincoln. Johnston,D.W. I956. The annualreproductive cycle of the CaliforniaGull. I. Criteriaof age and the testiscycle. Condor58: 134-162. Jones,P.A. 1986. Aspectsof the reproductivebiology of the CaliforniaGull in Alviso, California. M.A. thesis,San FranciscoState Univ. Jorde,D. G., Krapu,G. L., Crawford,R. D., and Hay, M.A. 1984. Effectsof weatheron habitat selection and behavior of Mallards in Nebraska. Condor 86: 258-265. Josselyn,M. 1983. The ecologyof the San FranciscoBay tidal marshes: A communitypro- file. U.S. Fish Wildl. Serv. FWS/OBS-83/23. Jurek, R. M. 1972. Californiashorebird survey, 1970-71. Spec. Wildl. Invest.Proj. Rept. Calif. Dept. FishGame, Sacramento. Jurek, R. M. 1973. Californiashorebird survey, 1969-74. Spec. Wildl. Invest.Proj. Final Rept. Calif.Dept. FishGame, Sacramento. Jurek,R.M. 1974. Californiashorebird survey 1969-74. Spec.Wild. Invest.Rept. Proj.W- 54-R, Job III-1. Calif.Dept. FishGame, Sacramento. Kelly,P. R., andCogswell, H. L. 1979. Movementsand habitat use by winteringpopulations of Willetsand Marbled Godwits, in Shorebirdsin marineenvironments (E A. Pitelka,ed.), pp. 15-32. StudiesAvian Biol. 2. King, D. B., Baumgartel,M., DeBeer, J., and Meyer, T. 1987. The birds of San Elijo Lagoon,San DiegoCounty, California. W. Birds18: 177-208. Kushlan,J. A. I981. Resourceuse strategies of wadingbirds. WilsonBull. 93: 145-163. Lenna,P. 1969. Short-billedand Long-billed Dowitchers in the PointReyes, California, area. PointReyes Bird Ohs. Newsl. 13. Leopold,A. S., and Smith, R. S. 1953. Numbersand winter distributionof PacificBlack Brant in North America. Calif. Fish Game 39: 95-101. Lidicker,W. Z., Jr., and McCollurn,E C. 1979. CanadaGoose established as a breeding speciesin San FranciscoBay. W. Birds 10: 159-I62.

252 WATERBIRDS .AT POINT REYES

Loftin,H. 1962. A studyof borealshorebirds summering on ApalacheeBay, Florida. Bird- Banding33: 21-42. Lowe-McConnell,R. H. 1967. Biologyof the immigrantCattle Egret Ardeola ibis in Guyana,South America. Ibis 109: 168-179. Ludwig,J.P. 1965. Biologyand structureof the CaspianTern (Hydroprognecaspia) populationof the GreatLakes from 1896-1964. Bird-Banding36: 217-233. Luther,J.S. 1980. Fourthreport of the CaliforniaBird Records Committee. W. Birds11: 161-173. Luther,J. S., McCaskie,G., and Dunn, J. 1979. Thirdreport of the CaliforniaBird Records Committee. W. Birds 10: 169-187. Luther,J. S., McCaskie,G., and Dunn, J. 1983. Fifth report of the CaliforniaBird Records Committee. W. Birds 14: 1-16. Maillard,J. 1904. A few recordssupplementary to Grinnell'scheck-list of Californiabirds. Condor 6: 14-16. Mais, K. E 1974. Pelagicfish surveysin the CaliforniaCurrent. Calif. Dept. Fish Game Fish. Bull. 162: 1-79. Major, J. 1977. Californiaclimate in relationto vegetation,in TerrestrialVegetation of California(M. G. Barbourand J. Major,eds.), pp. 11-74. Wiley,New York. Manolis,T. 1978. Statusof the BlackRail in centralCalifornia. W. Birds9: 151-158. McCaskie,R.G. 1965. The Cattle Egret reachesthe west coast of the United States. Condor 67: 89. McCaskie,G., DeBenedictis,P., Erickson,R., and Morlan, J. 1979. Birds of Northern California:An AnnotatedField List. 2nd ed. GoldenGate Audubon Soc., Berkeley. Moffitt, J. 1932. Secondannual Black Brant censusin California. Calif. Fish Game 18: 298-310. Moffitt, J. 1939. Notes on the distributionof WhistlingSwan and Canada Goose in California. Condor 41: 93-97. Moffitt,J. 1940. Thirdrecord of the KingEider in California.Condor 42: 305. Moffitt, J. 1941. Eleventhannual Black Brant censusin California. Calif. Fish Game 27: 216-233. Moffitt, J. 1943. Twelfth annual Black Brant censusin California. Calif. Fish Game 29: 19-28. Moffitt,J., and Cottam,C. 1941. Eelgrassdepletion on the Pacificcoast and its effectupon Black Brant. U.S. Fish Wildl. Serv. Wildl. Leaflet 204. Morlan, J. 1985. Eighthreport of the CaliforniaBird RecordsCommittee. W. Birds 16: 105-122. Morlan, J., and Erickson,R. 1988. Supplementto the Birdsof NorthernCalifornia, in McCaskie,G., DeBenedictis,P., Erickson,R., and Morlan, J. 1979. Birdsof Northern California:An Annotatec•Field List. 2nd ed. GoldenGate AudubonSoc., Berkeley. Reprintedwith supplement,April 1988. Morrison,R. I. G. 1984. Migrationsystems of someNew World shorebirds,in Shorebirds: Migration and Foraging Behavior (J. Burger and B. L. Olla, eds.), pp. 125-202. Behaviorof MarineAnimals. Vol 6. Plenum,New York. Morrison,R. I. G., and Harrington,B.A. 1979. Criticalshorebird resources in JamesBay and eastern North America. Trans. N. Am. Wildl. Nat. Resource Conf. 44: 498-507. Morrison,R. I. G., Harrington,B. A., and Leddy,L. E. 1980. Migrationroutes and stopover areas of North American Red Knots Calidris canutus wintering in South America. WaderStudy Group Bull. 28: 35-39. Murphy,G. I. 1966. Populationbiology of the Pacificsardine ($ardinops caerulea). Proc. Calif. Acad. Sci. 34: 1-84. Myers,J.P. 1980. SanderlingsCalidris alba at BodegaBay: Facts,inferences, and shame- lessspeculations. Wader Study Group Bull. 30: 26-32. 253 WATERBIRDS AT POINT REYES

Myers,g. P. 1981a. Cross-seasonalinteractions in the evolutionof sandpipersocial systems. Behav. Ecol. Sociobiol. 8: 195-202. Myers,g. P. 1981b. A testof threehypotheses for latitudinalsegregation of the sexesin winteringbirds. Can. J. Zool. 59: 1527-1534. Myers,g. P. 1983. Conservationof migratingshorebirds: Staging areas, geographic bottle- necks,and regional movements. Am. Birds37: 23-25. Myers,J.P., Maron,J. L., andSallaberry, M. 1985. Goingto extremes:Why do Sanderlings migrateto the Neotropics?,in NeotropicalOrnitholocdy (P. A. Bucldey,M. S. Foster,E. S. Morton,R. S. Ridgely,and E G. Buckley,eds.), pp. 520-535. Ornithol.Monogr. 36. Myers,g. P., Schick,C. T., and Hohenberger,C.g. 1984. Noteson the 1983 distributionof Sanderlingsalong the UnitedStates' Pacific Coast. WaderStudy Group Bull. 40: 22-26. Naylor,A. E. 1960. The WoodDuck in Californiawith specialreference to the useof nest boxes. Calif. Fish Game 46: 241-269. Nichols,D. R., and Wright, N.A. 1971. Preliminarymap of the historicmarshlands, San FranciscoBay, California. Open File Rept. Basic Data Contrib. 9, U. S. Geol. Surv., Menlo Park. Ohlendorf,H. M., Schaffner,E C., Custer,T. W., and Stafford,C. J. 1985. Reproduction and organochlorinecontaminants in terns at San Diego Bay. ColonialWaterbirds 8: 42-53. Oring, L. W., and Davis, W. M. 1966. Shorebirdmigration at. Norman, Oklahoma: 1961-63. Wilson Bull. 78: 166-174. Orr, E. D., Ward, R. M. P, Williams,N. A., and Brown,R.G. 1982. Migrationpatterns of Red and Northernphalaropes in the southwestDavis Strait and in the northernLabrador Sea. Wilson Bull. 94: 303-312. Orr, R.T. 1944. A coastalrecord of the EmperorGoose in California. Condor46: 90. Orr, R.T. 1950. A new North American recordfor the Tufted Duck. Condor 52: 140. Orr, R. T. 1962. The TuftedDuck in California. Auk 79: 482-483. Page,G. W., Bidstrup,E C., Ramer,R. J, and Stenzel,L. E. 1986. Distributionof wintering SnowyPlovers in Californiaand adjacentstates. W. Birds17: 145-170. Page, G., Fearis, B., and Jurek, R. M. 1972. Age and sex compositionof Western Sandpiperson BolinasLagoon. Calif. Birds3: 79-86. Page,G. W., Shuford,W. D., Evens,J. G., and Stenzel,L. E. 1983. The distributionand abundanceof aquaticbirds in wetlandsof the Point Reyesto Bodegaarea. A reportfor the Point Reyes-FarallonesMarine Sanctuary. P.R.B.O., 4990 ShorelineHwy., Stinson Beach, CA 94970. Page, G. W., and Stenzel,L. E., eds. 1981. The breedingstatus of the SnowyPlover in California. W. Birds 12: 1-40. Page,G., Stenzel,L. E., and Wolfe, C. M. 1979. Aspectsof the occurrenceof shorebirdson a centralCalifornia estuary, in Shorebirdsin marineenvironments (F. A. Pitelka,ed.), pp. 15-32. Studies Avian Biol. 2. Palmer,R. S., ed. 1962. Handbookof North AmericanBirds. Vol. 1. Loonsthrough Flamingos.Yale Univ. Press,New Haven. Palmer,R.S. 1967. Speciesaccounts, in The Shorebirdsof North America (G. D. Stout, ed.), pp. 143-267. VikingPress, New York. Palmer,R. S., ed. 1976a. Handbookof North AmericanBirds. Vol. 2, Waterfowl(Part 1). Yale Univ. Press,New Haven. Palmer,R. S., ed. 1976b. Handbookof North AmericanBirds. Vol. 3, Waterfowl(Part 2). Yale Univ. Press,New Haven. Parrish,R. H., Nelson,C. S., and Bakun,A. 1981. Transportmechanisms and reproductive successof fishesin the CaliforniaCurrent. Biol. Oceanogr.1: 175-203. Paulson,D. R. 1983. Fledglingdates and southwardmigration of juvenilesof someCalidris sandpipers.Condor 85: 99-101.

254 WATERBIRDS AT POINT REYES

Phillips,A. R. 1975. Whyneglect the difficult? W. Birds6: 69-86. Pienkowski,M. W., and Evans,P.R. 1984. Migratorybehavior of shorebirdsin the Western Palearctic,in Shorebirds:Migration and ForagingBehavior (J. Burgerand B. L. Olla, eds.),pp. 73-123. Behaviorof MarineAnimals. Vol. 6. Plenum,New York. Pienkowski,M. W., Fearns,P. N., Davidson,N. C., and Worrall,D. H. 1984. Balancingthe budget:Measuring the energy intake and requirementsof shorebirdsin the field, in CoastalWaders and Wildfowlin Winter (P. R. Evans,J. D. Goss-Custard,and W. G. Hale, eds.),pp. 29-56. CambridgeUniv. Press, Cambridge. Pitelka,E A. 1950. Geographicvariation and the speciesproblem in the shore-birdgenus Limnodromus. Univ. Calif. Publ. Zool. 50. Pitelka, E A., ed. 1979a. Shorebirdsin marine environments. StudiesAvian Biol. 2. Pitelka, E A. 1979b. Introduction:The Pacific Coast shorebirdscene, in Shorebirdsin marineenvironments (F. A. Pitelka,ed.), pp. 1-11. StudiesAvian Biol. 2. Prater,A.J. 1979. Shorebirdcensus studies in Britain, in Shorebirdsin marineenvironments (E A. Pitelka,ed.), pp. 157-166. Studiesin Arian Biol. 2. Prater,A. J. 1981. EstuaryBirds of Britainand Ireland. Poyser, Calton, England. Pratt, H. M. 1970. Breedingbiology of Great Blue Heronsand CommonEgrets in central California. Condor 72: 407-416. Pratt, H. M. 1972a. Nestingsuccess of CommonEgrets and GreatBlue Heronsin the San FranciscoBay region. Condor74: 447-453. Pratt, H. M. 1972b. Nestingsuccess of Great Blue Heronsand CommonEgrets at Audubon CanyonRanch in 1971. Am. Birds26: 699-702. Pratt,H.M. 1974. Breedingof Great BlueHerons and Great Egretsat AudubonCanyon Ranch, California,1972-73. W. Birds5: 127-136. Pratt, H. M. 1980. Directionsand timing of Great Blue Heron foragingflights from a Californiacolony: Implications for socialfacilitation of food finding. WilsonBull. 92: 489-496. Pratt, H. M. 1983. Marin County Californiaheron colonies:1967-1981. W. Birds 14: 169-184. Pritchard,D.W. 1967. What is an estuary:Physical viewpoint, in Estuaries(G. H. Lauff, ed.), pp. 3-5. Am. Assoc.Adv. Sci.Publ. 83. Ralph,C.J. 1969. An analysisof offshoremigration. Point Reyes Bird Obs. Newsl. 12. Ralph, C. J., and Ralph, C. R. 1958. Notes on the nestingof egretsnear San Rafael, California. Condor 60: 70-71. Ratti, J.T. 1981. Identificationand distributionof Clark'sGrebe. W. Birds 12: 41-46. Recher,H. R. 1966. Some aspectsof the ecologyof migrantshorebirds. Ecology 47: 393-407. Reinsen,J. V., Jr. 1978. Birdspecies of specialconcern in California.Wildl. Mgmt. Branch Admin. Rept. 78-1. Calif. Dept. FishGame, Sacramento. Reinsen,J. V., Jr., and Binford, L.C. 1975. Statusof the Yellow-billedLoon (Gavia adamsiOin the westernUnited States. W. Birds 6: 7-20. Richardson,S. L. 1980. Spawningbiomass and earlylife of northernanchovy, Engraulis mordax, in the northernsubpopulation off Oregonand Washington. Fish. Bull. 78: 855-876. Rienecker,W. C. 1985. An analysisof Canvasbacksbanded in California. Calif. FishGame 71: 141-149. Rigney,M., and Rigney,T. 1981. A breedingbird surveyof the southSan Franciscosalt pondlevee system. A reportto the San FranciscoBay Natl. Wildl.Refuge, P.O. Box 524, Newark,CA 94560. Ritter,J. R. 1969. Preliminarystudies of sedimentationand hydrologyin BolinasLagoon, Marin County,California, May 1967-June 1968. U.S. Dept. Int., Geol. Surv., Water ResourcesDiv., Menlo Park, CA.

255 WATERBIRDS AT POINT REYES

Ritter, J. R., and Brown, W. M, Ill. 1973. Bolinas Lagoon, Marin County, California. Summaryof sedimentationand hydrology,1967-69. U.S. Dept. Int., Geol. Surv.,Water ResourcesDiv., Menlo Park, CA. Roberson, D. 1980. Rare Birds of the West Coast of North America. Woodcock Publ., Pacific Grove, CA. Roberson,D. 1985. MontereyBirds. MontereyPeninsula Audubon Soc., Carmel,CA. Roberson,D. 1986. Ninth report of the CaliforniaBird RecordsCommittee. W. Birds 17: 49-77. Salt, G. W., and Willard, D. E. 1971. The huntingbehavior and successof Forster'sTern. Ecology52: 989-998. Sanderson,G.C. 1980. Conservationof waterfowl, in Ducks, Geese, and Swansof North America(E C. Bellrose,ed.), pp. 43-58. 3rd ed. Stackpole,Harrisburg, PA. Sanger,G.A. 1970. The seasonaldistribution of someseabirds off Washingtonand Oregon, with noteson their ecologyand behavior.Condor 72: 339-357. Sanger,G.A. 1973. Pelagicrecords of Glaucous-wingedand Herring Gullsin the North Pacific Ocean. Auk 90: 384-393. Schaffner,E C. 1985. RoyalTern nestingattempts in California:Isolated or significantinci- dents? W. Birds 16: 71-80. Schaffner, E C. 1986. Trends in Elegant Tern and Northern Anchovy populationsin California. Condor 88: 347-354. Schneider,D.C., and Harrington,B.A. 1981. Timinõof shorebirdmigration in relationto prey depletion.Auk 98: 801-811. Scott,J. M. 1971. Interbreedingof the Glaucous-wingedGull and WesternGull in the Pacific Northwest. Calif. Birds 2: 129-133. Senner,S. E., and Howe, M.A. 1984. Conservationof nearcticshorebirds, in Shorebirds: Breeding Behavior and Populations(J. Burger and B. L. Olla, eds.), pp. 379-421. Behaviorof Marine Animals. Vol. 5. Plenum,New York. Shaw, S. P., and Fredine,C. G. 1971. Wetlandsin the United States:Their extent and their value to waterfowl and other wildlife. U. S. Fish Wildl. Serv. Circ. 39. Shuford, W. D. 1982. Field checklistof the birds of Marin County, Alta California. P.R.B.O., 4990 ShorelineHwy., StinsonBeach, CA 94970. Sibley,C. G. 1952. Birdsof the southSan FranciscoBay region. San JoseState College, mimeo. 44 pp. Availableat P.R.B.O. Library,4990 ShorelineHwy., StinsonBeach, CA 94970. Sidle,J. G., Koonz,W. H., and Roney,K. 1985. Statusof the AmericanWhite Pelican:An update. Am. Birds 39: 859-864. Siegfried,W. R., 1970. Mortality and dispersalof ringed Cattle Egrets. Ostrich 41: 122-135. Siegfried,W. R. 1978. Habitatand the modernrange expansion of the Cattle Egret,in Wading birds(A. Sprunt IV, J. C. Ogden, and S. Winckler,eds.), pp. 315-324. Natl. AudubonSoc., Res. Rept. 7. Sloan, N. E 1982. Statusof breedingcolonies of White Pelicansin the United States through1979. Am. Birds36: 250-254. Smith, M., Steinbach,T., and Pampush,G. 1984. Distribution,foraging relationships and colonydynamics of the AmericanWhite Pelican,Pelecanus erythrorhynchos, in southern Oregonand northeasternCalifornia. Unpubl.ms. The NatureConservancy, 785 Market St., San Francisco,CA 94103. SowIs,A. L., DeGange,A. R., Nelson,J. W., and Lester,G. S. 1980. Catalogof California seabirdcolonies. U.S. FishWildl. Serv.,Biol. Serv.Prog. FWS/OBS 37/80. Spear,L. B. 1988. Dispersalpatterns of WesternGulls/tom SoutheastFarallon Island. Auk 105: 128-141.

256 WATERBIRDS AT POINT REYES

Spear, L. B., Penniman,T. M., Penniman,J. F., Carter, H. R., and Ainley, D. G. 1987. Survivorshipand mortality factors in a population of Western Gulls, in Ecology and behaviorof Gulls(J. L. Hand, W. E. Southern,and K. Vermeer,eds.), pp. 44-56. Studies Avian Biol. I0. Spratt, J. D. I98I. Statusof the Pacificherring (Clupea harenguspallasii) resourcein California1972 to 1980. Calif. Dept. FishGame FishBull. 171. Stallcup,R.W. 1976. Pelagicbirds of MontereyBay, California. W. Birds7: 113-136. Stenzel,L. E., Huber,H. R., andPage, G.W. 1976. Feedingbehavior and diet of the Long- billed Curlew and Willet. Wilson Bull. 88: 314-332. Stenzel,L. E., Kjelmyr,J. E., Page, G. W., and Shuford,W. D. 1989. Resultsof the first comprehensiveshorebird census of northernand centralCalifornia coastal wetlands, 8-12 September1988. A reportof PointReyes Bird Observatory,4990 ShorelineHwy., StinsonBeach, CA 94970. Stenzel,L. E., Page,G. W., Carter,H. R., andAinley, D.G. 1988. Seabirdmortality in Californiaas witnessedthrough 14 yearsof beachedbird censuses. Final Report to the Gulfof the FarallonesNational Marine Sanctuary, Fort Mason #20I, San Francisco,CA 94123. Stenzel,L. E., Peaslee,S.C., and Page, G.W. 1981. Part 1I. MainlandCoast, in The breedingstatus of theSnowy Plover in California(G. W. Pageand L. E. Stenzel,eds.), pp. 6-16. W. Birds 12: 1-40. Stephens,A. B. 1931. Audubonnotes. Gull 13(7). Stephens,L, A., andPringle, C. C. 1933. Birdsof MarinCounty. AudubonAssociation of the Pacific,San Francisco. Avialable at P.R.B.O.Library, 4990 ShorelineHwy., Stinson Beach, CA 94970. Stone,K., and Rigney,M. 1978. The reproductivesuccess of three speciesof herons nestingon Bair Island,San Mateo County,1978. Reportto San FranciscoBay Natl. Wildl. Refuge,P.O. Box 524, Newark,CA 94560. Stoner,E. A. 1934. Recentoccurrence of the AmericanEgret in the San FranciscoBay region. Condor 36: 57-59. Storer,R.W. 1951. The seasonaloccurrence of shorebirdson BayFarm Island, Alameda County, California. Condor 53: 186-193. Storer,T. 1. 1915. Additionalrecords of the CaliforniaClapper Rail and Red Phalarope in California. Condor 17: 98. Swarth,C. W., Akagi,C., andMetropulos, P. 1982. Thedistribution patterns and ecology of waterbirdsusing the CoyoteHills saltponds. Reportto San FranciscoBay Nafi. Wildl. Refuge,P.O. Box 524, Newark,CA 94560. Takekawa,J. E., Carter,H. R., andHarvey, T. E. In press. Declineof the CommonMurre Uria aalge) in centralCalifornia. StudiesAvain Biol. Townshenri,D. J. 1985. Decisionsof a lifetime:Establishment of spatial defence and movement patterns by juvenile Grey Plovers (Pluvialis squatarola). J. Anim. Ecol. 54: 267-274. Unitt, P. 1977. The Little Blue Heron in California. W. Birds 8: 151-154. Vander Have, T. M., Nieboer,E., andBoere, G. C. 1984. Age-relateddistribution of Dunlin in the DutchWadden Sea, in CoastalWaders and Wildfowlin Winter (P. R. Evans,J. D. Goss-Custard,and W. G. Hale,eds.), pp. 160-176. CambridgeUniv. Press, Cambridge. Vermeer,K. 1970. Breedingbiology of Californiaand Ring-billedGulls. Can. Wildl.Serv. Rept. Ser. 12. Vermeer,K., and Bourne,N. 1984. The White-wingedScoter diet in BritishColumbia waters:Resource partitioning with otherscoters, in Marinebirds: Their feedingecology andcommercial fisheries relationships (D. N. Nettleship,G. A. Sanger,and P. F. Springer, eds.),pp. 30-38. Proc.Pac. SeabirdGroup Syrup., Seattle, 6-8 Jan 1982. Ver Planck,W. E. 1951. Salinesin the Bay Area, in Geologicguidebook of the San FranciscoBay counties,pp. 219-222. Calif. Div. Mines.Bull. 154.

257 WATERBIRDS AT POINT REYES

Wahl, J. R. 1975. Seabirdsin Washington'soffshore zone. W. Birds6: 117-134. Warriner,J. S., Warfiner,J. C., Page, G. W., and Stenzel,L. E. 1986. Mating systemand reproductivesuccess of a smallpopulation of polygamousSnowy Plovers. WilsonBull. 98: 15-37. Wheeler,R.J. 1965. PioneeringBlue-winged Teal in California,Oregon, Washingtonand British Columbia. Murrelet 46: 40-42. Williams,A., and Miller, G. W. 1963. A Trumpeter Swan in Marin County, California. Condor 65: 69. Willett, G. 1933. A revisedlist of the birdsof southwesternCalifornia. Pac. Coast Avifauna 21. Wilson,J. R. 1981. The migrationof High Arctic shorebirdsthrough Iceland. Bird Study 28: 21-32. Winlder,D. W., Weigen,C. P., Engstrom,E B., and Burch,S. E. 1977. Ornithology,in An ecologicalstudy of Mono Lake, California(D. W. Winlder,ed.), pp. 88-113. Inst.Ecol. Publ. 12. Univ. of Calif., Davis. Winter,J. 1973. The CaliforniaField Ornithologists Records Committee report 1970-1972. W. Birds 4: 101-106. Winter, J., and Erickson,D. 1977. The winter season. Middle PacificCoast region. Am. Birds 31: 367-372. Winter, J., and McCaskie, G. 1975. 1973 report of the California Field Ornithologists Records Committee. W. Birds 6: 135-144. Woodbury,A.M., and Knight,H. 1951. Resultsof the Pacificgull color-bandingproject. Condor 53: 57-77. Yocum,C. E, and Harris, S. W. 1975. Status,habitats, and distributionof birdsof north- westernCalifornia. HumboldtState Univ. Bookstore,Arcata, CA. Yocum,C. E, and Wooten,W.A. 1956. Blue-wingedTeal in Del Norte County,California. Calif. Fish Game 42: 81. Zwarts,L. 1976. Density-relatedprocesses in feedingdispersion and feedingactivity of Teal Arias crecca. Ardea 64: 192-209.

Accepted 1 September 1989

APPENDIX

The followingaccounts are of waterbirdspecies from PointReyes not detected on censusesbecause of their extremerarity or their preferencefor non-estuarine habitats. We have includedmany species with strongaffinities for offshoreand oceanicwaters when they have been recordedalive onshoreor when seen with someregularity from shore. Becausethey are generallyassociated with the open ocean we have excludedall Procellariiformes,although species such as the Sooty Shearwatercan be abundantin inshorewaters here. Additionalspecies that have been seenat sea off Point Reyesor have been recordedfrom beach-castspeci- mens are the Short-tailedAlbatross, Black-looted Albatross, Laysan Albatross, Northern Fulmar,Mottled Petrel, Murphy'sPetrel, Cook's Petrel, Pink-looted Shearwater,Flesh-looted Shearwater, Buller's Shearwater, Short-tailed Shearwater, Black-ventedShearwater, Wilson's Storm-Petrel, Fork-tailed Storm-Petrel, Leach's Storm-Petrel,Black Storm-Petrel,Long-tailed Jaeger, South Polar Skua, Arctic Tern, Craveri'sMurrelet, ParakeetAuklet, CrestedAuklet, and Horned Puffin.

258 WATERBIRDS AT POINT REYES

Their statusin watersoff Point Reyesis coveredby referenceson pelagicspecies in California(Ainley 1976a, Stallcup1976, Sowlset al. 1980, Roberson1985, Briggset al. 1987) or more generalavifaunal works discussing northern California (Grinnelland Miller 1944, McCaskieet al. 1979, Morlan and Erickson1988).

Yellow-billedLoon (Gayla adarnsii) Six Point Reyesrecords, all of singlebirds: five for TomalesBay from 13 Nov to 1 Jan, 1967 to 1983, and one for Drake'sEstero on 13 Apr 1983 (CBRC). Detailsof a TomalesBay reportfor 25 Jan 1971 (AB 25: 620) havenot beensub- mittedto the CBRC; an additional4 Point Reyesreports have beenrejected by the CBRC. Firstrecorded in Californiain 1967, now occursannually in the statewith 42 acceptedrecords of singlebirds (CBRC). Yellow-billedLoons have been found in Californiawaters every month of the year,but mostbirds occur from from Dec throughApr (Remsenand Binford 1975, CBRC). They usuallyprefer large bays, estuaries,inshore ocean waters, or, occasionally,freshwater lakes. Red-lootedBooby ($ula sula) An immaturewas seen from the mouth of San FranciscoBay north to Bolinas (14 Oct) from 13 to 18 Oct 1987 until pickedup sick and broughtto a wildlife rehabilitationcenter on 18 Oct (CBRC,AB 42: 128, ABN). This was 1 of 4 (pos- sibly5) Red-lootedBoobies sighted off Californiain fall 1987, and 1 of a total of 7 acceptedrecords for California(since 1975), all in fall from 26 Aug to 15 Nov, exceptfor one for 22 May 1985 (CBRC).

MagnificentFrigatebird (Fregata magnificens) There are at least5 inshoreor estuarinerecords for Point Reyesinvolving at least 7 birds (mostly iramatures)from 12 Jul to 26 Aug (ABN, PRBO). MagnificantFrigatebirds occur in coastalwaters of northernCalifornia primarily as post-breedingdispersants from Mexico and mostlyfrom mid-Julto early Sep (ABN). Extremedates are 20 Jun and 20 Oct (Grinnelland Miller 1944, ABN), exceptfor 3 winterrecords (McCaskie et al. 1979, AB 34: 302, AB 40: 519).

Least Bittern (Ixobrychusexilis) Three recordsfor Point Reyes: 1 adult at Drake's Beach pond on 18 Sep 1980 (AB 35: 220), 1 at Olema Marsh on 27 Dec 1967 (ABN: RS), and 1 at Olema Marsh on 29 Jan 1969 (AB 23: 515). Occursirregularly on the northern Californiacoast with recordsfor every month (ABN, Grinnell and Wythe 1927, Roberson1985). Interior breedingpopulations have declined,owing to habitat loss(Reinsen 1978).

White-facedIbis (Plegadischihi) Two fall records:singles at Drake's Esteroon 12 Oct 1978 (AB 33: 210) and on "PointReyes" on 6 Oct 1985 (ABN: RMS). Localspring records, all in 1988 and perhapsinvolving the samebirds: 15 birdsflying south by CypressGrove, near Marshall,Tomales Bay, on 20 May (ABN: JPK), up to 12 at Bolinassewer pondson 25 and 26 May (DDeS et al.), and 4 on outerPoint Reyes on 26 May (ABN: RS). The birds were observedat freshwaterponds and marshesand in flight. On the northernCalifornia coast White-faced Ibises occur almost annually in fall from 9 Aug to 19 Nov, exceptfor 1 birdthat lingeredfrom 11 Oct to 28 Dec; there are 5 additionalwinter records, 25 Dec-20 Mar (ABN, Roberson 1985).

259 WATERBIRDS AT POINT REYES

Fall recordsare usuallyof 1-3 birds, rarely up to 15; maximumfor winter is 31. Springrecords, of flocksup to 57 birds,extend from 3 May to 20 Jun with most from mid- to late May (ABN, Roberson 1985). Formerly accidentalon the northernCalifornia coast in springuntil seen in 5 of 7 yearsfrom 1981 to 1987 (ABN). A major coastalinflux in spring 1988 involvedabout 15 widespread records of about 300 birds total (ABN). Until recently, White-faced Ibis had declined markedly in California (Grinnell and Miller 1944, Remsen 1978). Breedingibises expanded their rangeand increasedtheir populationin the interior of California(ABN) and Oregon(Ivey et al. 1988) duringa wet periodfrom 1982 to 1985, when floodingmay have displacedbreeding ibises from Great Salt Lake (Iveyet al. 1988). The 1988 influxto coastalCalifornia may havebeen prompted by recentcolonizers abandoning marshes in the interiorof the statethat driedup duringthe droughtin 1987 and 1988. TrumpeterSwan (Cygnusbuccinator) The onlyPoint Reyes record, of a singlebird at Abbott'sLagoon from 1 Jan to 9 Mar 1962 (Williams and Miller 1963, Dunn 1988), is one of a total of 11 acceptedrecords for Californiainvolving I9 birdson datesspanning 8 Nov to I5 Mar, 1935 to 1987 (CBRC).

YellowRail (Coturnicopsnoueboracensis) There are 7 old specimenrecords for Point Reyesfrom marshesat the south end of TomalesBay, 27 Oct-22 Feb, 1898 to 1936, 4 in 1905 alone (CAS and MVZ, fide CBRC). Not yet reviewedby the CBRC, an additional5 specimensfor "Point Reyes," 27 Oct-27 Dec I905, are at the American Museumof Natural History,New York (numbers354496, 354497, 354499, 354500, 354502, fide SNGH). Likely there are further specimensfrom the area at other eastern museums. The few recent local recordshave all been of singlebirds from the south end of TomalesBay duringwinter flood tides: 1 on 3 Dec 1986 (AB 41: 323, CBRC); 1 on 2 Dec 1987 (AB 42: 316) and 1 droppedby a Great Egretand retrieved on 21 Dec 1987 (AB 42: 316, CAS 84063) (both under review by CBRC as one record);details of a report on 13 Feb 1961 (AFN 15: 354-355) have not been submittedto the CBRC. The acceptedPoint Reyes recordsare among 52 (all but 5 prior to 1937) of birds wintering at tidal or freshwater marsheson the coastor in the interiorfrom 2 Oct to 10 Apr (CBRC). Although this rail was formerlyconsidered rare in California(Grinnell and Miller 1944), the number of old recordsand its secretivehabits suggesta substantialpopulation once winteredon the coast. The probableextirpation of breedingpopulations in the interior of California (Remsen 1978) and declineselsewhere may explain the apparentdecline of the coastalwintering population. Recent coastalwintering recordsand the discoveryof breedingpopulations in southernOregon (AB 36: 999, 38: 1042), however, may presage a limited resurgenceof California's population.

Mountain Plover (Charadrius montanus) One estuarinerecord from LimantourEstero on 10 Feb 1967 (AFN 21: 454). Additionally,at least26 birdshave been found in pasturesand plowedfields from 2 Oct to 1 Jan in 5 years from 1978 to 1988 (ABN). All local recordsinvolve I-3 birds,except for a flock of 2I at the RCA Station,Point Reyeson 2I Oct 1983 (AB 38: 242, ABN). Transientand winteringbirds occur irregularly on the coastalslope of northernCalifornia from 22 Sep to 10 Feb (ABN). Has decreased historicallyin California(Grinnell and Miller 1944).

260 WATERBIRDS AT POINT REYES

EurasianDotterel (Charadrius rnorinellus) Two recordsof singlejuveniles in pasturelandon outer Point Reyes:6-9 Sep 1986 (AB 41: 138-139, CBRC) and 10-13 Sep 1988 (AB 43:27 and 163; underreview by CBRC). The only other recordfor Californiais of a juvenileon SE FarallonIs. from 12 to 20 Sep 1974 (Henderson1979, Lutheret al. 1979). BlackOystercatcher (Haernatopus bachmani) A year-roundresident of rockyreefs, seastacks, and offshoreislets on the outer coastof Point Reyes. Fairly evenlydistributed along rocky shorelineduring the breedingseason, when a minimumof 8 pairs inhabitPoint Reyes(Sowls et al. 1980). Breedinghas been confirmedat TomalesPoint, ChimneyRock, Double Point, and betweenPoint Resistanceand Miller's Point (Stephensand Pringle 1933, ABN, DS). Distributionmore clumpedin winter,especially when the rocky shorelineis extensivelywave-washed during storm tides, concentratingroosting birds. Flocksof up to 20 birds have been recordedin winter at TomalesPoint (ABN). Birdsoccasionally stray for brief periodsto sandybeaches and estuarine shorelines,usually those near their rockyshoreline haunts. SolitarySandpiper (Tringa solitaria) Occurson Point Reyesalmost annually in fall from 4 Aug to 29 Sep (ABN), with an outlyingdate of 19 Oct 1984 (RMS). Most fall birdsare juveniles,of which the earliestreported date is 6 Aug 1988 (ABN: LJP). Two local spring records: 2 birds on BolinasMesa on 2 May 1974 (AB 28: 847) and 1 at the Bolinassewer ponds from 5 to 6 May 1980 (DS et al.). One at a freshwaterpond near Invernessfrom 22 Jan to 14 Mar 1984 (AB 38: 353, 954) is the onlywinter recordfor northernCalifornia (McCaskie et al. 1979, Morlan and Erickson1988) and one of few for the state as a whole (Garrett and Dunn 1981). On the northernCalifornia coast dates of transientSolitary Sandpipers in fall extendfrom 19 Jul to 19 Oct with a peak from late Aug to mid-Sep(ABN). Springdates range from 9 Apr to 24 May with a peak in late Apr and early May (ABN). Solitary Sandpipersare generallyless numerouson the coast in spring than in fall, but sincethe mid-I980s they havebeen seenon the north coastwith regularityand in increasingnumbers in spring(Morlan and Erickson1988, ABN). They frequent the marginsof freshwaterponds, sewer ponds, reservoirs, stock ponds, or slow- moving streams. Little Stint (Calidris rninuta) The only Point Reyesrecord, of a juvenileat the Bolinassewer ponds from 14 to 22 Sep 1983 (Roberson1986), is 1 of 2 currentlyaccepted records of the speciesfor California(CBRC). White-rumpedSandpiper (Calidris fuscicollis) One Point Reyes record of a singlebird at Kehoe Beach on 11 Jun 1978 (Lutheret al. 1983). This is amonga total of 9 acceptedrecords for California, 1969 to 1986:7 in springfrom 17 May to 16 Jun; 2 in fall from 15 Aug to 18 Sep (CBRC). Sharp-tailedSandpiper (Calidris acurninata) One old Point Reyesrecord from Olema on 27 Nov 1870 (Grinnelland Miller 1944); 16 laterrecords of 18 birds(all juveniles) on PointReyes from 21 Sep to 22 Nov, 1966 to 1988. Now recordedannually in coastalnorthern California (all 261 WATERBIRDS AT POINT REYES

juveniles)from 2 Sep to 27 Nov (mostfrom late Sep to earlyNov), exceptfor 1 bird remainingon a saltpond in southSan FranciscoBay from I7 Nov I985 to 5 Jan 1986 (AB 40: 326). Rock Sandpiper(Calidris ptilocnemis) Fourrecords for PointReyes, all of singlebirds: 25 Oct I966 at AbalonePoint (AB 21: 74), 27 Feb 1975 at DuxburyReef (AB 29: 737), 29 Nov 1980 at RCA Beach, Bolinas(ABN: CSw), and 20 Dec 1986 at Walker Creek mouth, Tomales Bay (AB 41: 324). All were on rocky substrateon the outer coastexcept the TomalesBay bird, which, atypically,was on tidal mudfiats. Dates of occurrence on the northernCalifornia coast span I5 Oct to 9 May with most recordsfrom Nov to mid-Apr (ABN).

Buff-breastedSandpiper (Tr•,ngites subrufico!lis) Seven acceptedrecords for Point Reyesof 21 birdsfrom 24 Aug to 29 Sep, 1977 to 1987 (CBRC),with a high countof 11 birdsat TomalesPoint from 26 to 31 Aug 1978 (Lutheret al. 1983). Additionallya recordof 5-10 birdson Point Reyes from 9 to 11+ Sep 1988 is under review by the CBRC. All birds frequentedpastures, or low marsh vegetationon the sandyshores of Abbott's Lagoon. Exceptfor the firststate record, 14 Sep 1923 (Grinnelland Miller 1944, CBRC), and the lone spring record, 3-4 May 1980, dates of all accepted Californiarecords range from 23 Aug to 22 Oct, 1964 to 1987 (CBRC). Buff- breastedSandpipers have been recordedannually and in increasingnumbers in California since 1975.

PomarineJaeger ($ter½orarius pomarinus) Pomafine Jaegersoccur primarilyat sea off central California, where they favorwaters seaward of the continentalshelf during migration (Briggs et al. 1987). They occur mostlyas fall migrantsfrom mid-Julto early Nov (peak late Aug to early Oct), secondarilyas springmigrants from mid-Apr to late May, and sparingly as winter residents;they are irregularin summer(Stallcup 1976, Roberson1985, Bfiggs et al. I987). Althoughoutnumbered by ParasiticJaegers close to land, Pomafinesare seen from shoreover the inshorezone and sparinglyin large bays and estuaries, on Point Reyes primarily in Sep and Oct (ABN). Nearshore sightingsin fall coincidewith greatestoffshore abundance of this jaeger, peak numbersof ElegantTerns near shore,and greatestobserver coverage. Pomafines have been seen on 9 of 19 Point ReyesCBCs from 1970 to 1988, with a high count of 4 in 1985.

Little Gull (Larus minutus) A Point Reyesrecord of 1 bird at TomalesBay on 21 Nov 1984 is among32 acceptedrecords for Californiafalling in every month, but mostlyOct to May, 1968 to 1987 (CBRC). Annual sightingsin California since 1977 parallel increaseselsewhere, including recent breedingin North America (AOU 1957, 1983).

Common Black-headedGull (Larus ridibundus) The onlyPoint Reyes record is of a singlebird at TomalesBay from 5 to 8 Apr 1976 (Lutheret al. 1979). This is 1 of 13 acceptedCalifornia records, 1954 to 1986, all falling betweenSep and Apr except for singleJun and Jul records (CBRC).

262 WATERBIRDS AT POINT REYES

Sabine'sGull (Xema sabini) The Sabine'sGull typicallyinhabits offshore and oceanicwaters off California duringmigration. It occursprimarily in fall from Aug throughOct (peakSep and early Oct) and in springin Apr and May (peak mid-May),exceptionally in mid- winter or mid-summer(Ainley 1976a, Stallcup1976, Roberson1985, Briggset al. 1987). Seen irregularlyfrom shoreat Point Reyes,mostly in fall (ABN). Two winter recordsfrom inshoreat Point Reyes: I immatureat Limantouron 15 Dec 1968 (AFN 23: 516); 2 iramaturesoff Point ReyesBeach during a storm on 4 Jan 1978 (AB 32: 396).

RoyalTern (Sterna maxima) A northward dispersant from Mexico to estuarine and inshore waters in California. Althoughvariable in timingand abundance,Royal Terns formerly were "fairlycommon" off Californiafrom Sep to Mar, thoughrecorded in everymonth (Grinnelland Miller 1944). A 23 Nov 1918 specimenfor HumboldtBay (Yocum and Harris 1975) is the only evidenceof former occurrencenorth of TomalesBay (Grinnelland Miller 1944). Specimenrecords for Point Reyes are of 1 bird at Bolinason 17 Oct 1893 (CAS 43313) and 4 from BolinasBay: 3 on 9 Jan 1926 (MVZ 1922, 1923, 1932) and 1 on 20 Jan 1927 (MVZ 2783). There are no validrecent records for Point Reyes. See ElegantTern for discussionof a major declineof Royal Terns at the time of a great increaseof ElegantTerns beginning in the 1950s. RoyalTerns now occurcasually in northernCalifornia north to San FranciscoBay from Mar throughOct (Morlanand Erickson1988, ABN).

Least Tern (Sterna antillarum) Two Point Reyes records,both from BolinasLagoon: 1 on 27 Apr 1980 (LES)and 1 in "fall" 1987 (KH). Theselikely represent birds from San Francisco Bay, which currently supports the only breeding colonies of Least Terns in northernCalifornia (McCaskie et al. 1979, Morlan and Erickson1988). Dates of occurrencein northern California span 27 Mar to 16 Oct, but Least Terns are scarcein this regionbefore mid-Apr and after earlySep (ABN). LeastTerns found irregularlyin springor fall north of the GoldenGate from 23 Apr to 13 Sep (ABN) likelyrepresent overshooting migrants or post-breedingdispersants. Least Terns have declineddramatically as breederson the Californiacoast and are currenfiy listedas endangeredby both stateand federalgovernments.

PigeonGuillemot (Cepphus columba) About140 pairsbreeds on cliffs,sea stacks, and offshore islets along the Point Reyesshoreline (SowIs et al. 1980). Theyforage inshore almost exclusively within 5 km, andmostly 1-2 km, of land(Briggs et al. 1987). Breedersbegin to arrivein numbersby mid-Mar,remain common through Aug, and thereafterdwindle to winterlows by mid-Oct,when most that remainare young(ABN). A countof 19 juvenilesin Drake'sBay on 10 Oct 1980 (DS)is highfor late fall, and a countof 26 at TomalesPoint at the mouthof TomalesBay, the onlylocale on PointReyes whereguillemots winter regularly, on 6 Jan 1979 (DS) is high for mid-winter. Guillemotswere recordedon 10 of 19 Point ReyesCBCs from 1970 to 1988 with 1-3 guillemotsin 6 years,10-13 in 3 years,and 42 in 1 year. Guillemot populationson the Faralloneshave recovered from declines caused probably by oil pollution(Ainley and Lewis 1974) 263 WATERBIRDS AT POINT REYES

MarbledMurrelet (Brachyramphus marmoratus) A year-roundresident along the northernCalifornia coast with birdsnesting in old-growthforests up to 40 km inland and foragingin nearshorewaters mostly within 1-2 krn of land (Carter and Erickson1988). Occursin nearshorewaters of Point Reyesmostly from Aug to Mar (ABN). Althoughbirds have been seen off Point Reyesin the breedingseason (1 Apr-1 Sep; Carter and Erickson1988), a lackof nearshorerecords from 2 May to 30 Jun and a total lackof inlandrecords suggeststhat Marbled Murrelets do not breed regularlyin the Point Reyes area despitethe availabilityof seeminglysuitable nesting habitat. Local Jul and Aug records probably pertain to post-breedingdispersants from elsewhere. The Californiapopulation of MarbledMurrelets has probablydeclined because of the destructionof old-growthforests, although the speciesis alsosusceptible to mor- talityfrom gillnetting and oil pollution(Carter and Erickson1988). Xantus' Murrelet($ynthliborarnphus hypoleucus) A bird hit by a car about 2 km north of Bolinas on 28 Aug 1973 (PRBO specimen736) and anotherin Drake'sBay seenfrom shoreon 9 Oct 1987 (ABN: RS) constitutethe only Point Reyesnearshore records. Xantus'Murrelets typically occupywaters 20 to 100 km off the northernCalifornia coast, primarily from Jul to Oct (Roberson1985, Briggset ai. 1987) and irregularlyduring the remainderof the year (McCaskieet al. 1979). With an increasein boat trips sincethe 1970s, Xantus' Murreletsare now seen with regularityin waterswest of the Farallones and near the Cordell Banks off Point Reyes (ABN). Recent late May and Jun sightingsthere indicate rapid northward post-breedingdispersal (Briggs et al. 1987, D. G. Ainley pers. comm.). Ancient Murrelet ($ynthliboramphusantiquus) These murreletsoccupy inshore and offshore waters off Point Reyes from mid-Septhrough Apr, but mostlyNov to Mar; there are only 4 May-Aug records (ABN). Numbersfluctuate greatly from year to year apparenfiybecause of varying ocean conditionsand the species'preference for cold waters (Ainley 1976a). AncientMurrelets have been recordedon 14 of 19 Point ReyesCBCs from 1970 to 1988; the outlyinghigh count of 155 excluded,the mediannumber for 13 yearswas 15 (range2-49). Of the 155 birdson 17 Dec 1988, 150 were seen from a boat plyinginshore waters from TomalesPoint to the Point Reyeshead- lands(KH).

Cassin'sAuklet (Ptychoramphusaleuticus) Year round this auklet occupies California waters mostly from the mid-continentalshelf to about 150 km from land (Briggset al. 1987). In late springand summerbirds concentrate around colonies (Briggs et al. 1987), particularly the Faralloneswhich support80% of the Californiapopulation (Sowis et al. 1980). They rangemore widelyduring post-breeding dispersal from Aug to Oct, and the state's populationat least doublesin winter with immigrantsfrom the north (Briggset ai. 1987). Cassin'sAuklets are rarelyseen close to shoreat Point Reyes,usually during or after winter storms;they were recordedon only 6 of 19 Point ReyesCBCs from 1970 to 1988 (range0-15). RhinocerosAuklet (Cerorhinca monocerata) RhinocerosAuklets inhabit neritic and oceanicwaters of centralCalifornia year round,particularly seaward of the continentalshelf break (Briggs et al. 1987). The 264 WATERBIRDS AT POINT REYES smallnesting population of thisregion is swelledgreatly in winterby influxesfrom the north. Off Point Reyesgreatest numbers occur from mid-Octto mid-Apr (ABN). Breedingpopulations are now increasingin Californiaand elsewhereon the West Coast (SowIset al. 1980, Briggset al. 1987). Since 1977, up to 11 birdsat a time have been observedon the water belowthe Point Reyesheadlands in May and Jun (ABN). These birdshave been observed"billing" and in passing flightsthat suggestlocal breeding. Tufted Puffin (Fratercula cirrhata) Tufted Puffinsoccur in neritic and oceanicwaters off Californiayear round, thoughnumbers are much greaterin winter than duringsummer (Briggs et al. 1987). At sea in any seasonbirds are mostnumerous seaward of the continental slope,with a few birdsas far from shoreas 180 km. Breedingpopulations of TuftedPuffins are now expandingor becomingre-established in Californiaafter decliningearly in this century,perhaps because of oil pollution(Ainley and Lewis 1974, SowIset al. 1980). Formerlythey were suspectedof breedingon "Point Reyes"and at Bird Rock,Tomales Point (Stephens and Pringle1933, Grinnelland Miller 1944), but a subsequentlack of reports may have been due to limited observercoverage or actualdecline. Since1976 up to 6 birdsat a time havebeen seenin the vicintyof the PointReyes headlands each year from mid-Aprthrough Jul (ABN). Thesebirds have been seenin passingflights, gathering algae, and car- wing foodup to cliffs,but no nestshave been found because the sitesare inacces- sible. Many birdsin oceanicwaters off Point Reyesduring the nestingseason probablycome from the importantFarallon colony.

265 PectoralSandpiper Sketch by Sven Achtermann

266