WESTERN BIRDS

Volume 12, Number 1, 1981

THE BREEDING STATUS OF THE SNOWY PLOVER IN

GARY W. PAGE and LYNNE E. STENZEL, Editors, Point Reyes Bird Observatory, 4990 Shoreline Highway, StinsonBeach, California94970

The westernrace of the Snowy Plover (Charadriusalexandrinus nioosus) breeds on the Pacific coast from southern Washington to southern Baja California, inland in Oregon, California, Nevada, Utah, Colorado, New Mexico, Kansas, Oklahoma and Texas, and along the coastsof Texas and northeasternMexico (AOU 1957). For many yearsornithologists believed that the number of Snowy Plovers breeding along the Pacific coast was decliningas developmentdestroyed suitable . In May, June and July, from 1977 to 1980, Point Reyes Bird Observatory(PRBO) biologistsand volunteers conducted surveys of potential breeding habitat throughout Californiato gather informationon the distributionand abundanceof Snowy Plovers.This paper summarizesthe resultsof thosesurveys and the available data on the species'past abundanceand distribution.We attempt to define suitablebreeding habitat and to describethe effectsof human activitieson it. Detailedstudies of marked birdsundertaken by John and Jane Warriner at Pajaro Dunes on MontereyBay have been very helpfulin interpretingthe surveyresults. Their informationon migrationperiods, mid-breedingseason movements and the detection rate of birds on censuses is summarized in this paper. Detailed information on the occurrence of birds at specificsites is available in a report (Page and Stenzel 1979) on file with the California Department of Fish and Game in Sacramento. If readers have information indicatinggreater breeding numbers or know of breedingsites not mentioned here, we and the Departmentof Fishand Game encouragethem to contactus.

METHODS The breedingsurvey covered the coastbetween the and the Oregon border in 1977, the remainder of the California coastand interior in 1978, and the ChannelIslands from 1978 to 1980. A listof all sitessurveyed on the mainlandcan be derivedfrom Appendices1 and 2. SusanPeaslee and Gary Page, with occasionalhelp from others,covered the coastfrom the Golden Gate to the Oregonborder between 16 May and 11 June 1977. From USGS topographicalmaps they locatedbeaches ap- Western Birds 12:1-40, 1981 1 SNOWY PLOVER BREEDING STATUS pearingto have sand or pebblehabitat above the high water mark. They surveyedthese beaches, starting in Marin County and proceedingnorth to Del NorteCounty. Additional censuses to recheckcertain beaches during the last3 dayswere taken in HumboldtCounty. On everybeach all openhabitat was checkedand heavilyvegetated or litteredareas were sampled.Physical characteristics,vegetation, debris cover, evidence of nest predators, and level of human disturbancewere recorded. The age and sex of Snowy Ploverswere determinedwhen possible.Adult maleswere distinguishedby their blackforehead, cheek and shoulderplumage; some males also had a distinctiverusty cap whichfemales lacked. Adult females were recognized by brownerfeathering in theseregions, and juvenilesby distinctivepale edgings on wing coverts.We attemptedto find the nestsof all birdswhose behavior suggestedthey might be incubating.Descriptions of each nest includedthe presenceor absenceof nearby objects,substrate type, distancefrom water and opennessof habitatwithin a 10 m radius. Broods of chicksalso were locatedand the sizeand numberof youngrecorded. In some areasit was impossibleto detectall plovers,and estimateswere made to partiallycorrect for missedbirds. We usedfour methodsto estimate the numberof breedingpairs: 1) total adultsdivided by 2; 2) totalpairs seen; 3) total singlefemales or maleswith nestsor broods;and 4) total pairsseen plussingle adults with nestsor broods.For eacharea the methodresulting in the highestnumber of pairswas used. From 8 May to 26 June and on 9 July 1978 Lynne Stenzeland Susan Peasleemade censusesor spotchecks of beaches,lagoons, river mouths and bars, bay shores,salt pans and saltworksalong the coastbetween Border Field, County, and the Golden Gate. Suitableareas for censuses were selectedfrom USGS topographicalmaps, referencesin the literature, and many unpublishedfield observations.Only in Los Angeles County, where we assumedbeach groomingactivities precluded the possiblityof nesting,did we knowinglyexclude some sand beach from our survey.Our findingson the similarlygroomed beaches of OrangeCounty and a descrip- tion of how groomingmakes plover nestingvirtually impossible are reported in the results.Although the surveyprogressed from southto north, therewas some back-trackingor skippingahead so that censusescould be made at heavilyused areas on weekdaysand at restrictedaccess areas on weekends. Survey methods were similar to those used in 1977 except that nest descriptionswere more detailed and included information on the topographicrelief within 1 and 10 m. A searchwas made for nestsand broodsto establishevidence of breedingin each locality, but to minimize survey time and disturbance,particularly in Least Tern ($terna albifrons) nestingareas, no attempt was made to locate all nests. The interiorsurvey lasted from 26 April until 13 July 1978. PhilipHender- sonfirst checked areas in the San JoaquinValley and aroundthe SaltonSea. He thengenerally moved northward, working alone until 1 Junewhen Gary Pagejoined him in Inyo County.Potential breeding areas were selected from USGS topographicalmaps, from ornithologicalliterature and from discus- sionswith personsfamiliar with the distributionof Californiabirds. Alkaline lakesparticularly were soughtout, but if theselacked standing water they were not surveyedbecause plovers were assumedto be absent. SNOWY PLOVER BREEDING STATUS

Survey methodsvaried accordingto each area's physicalcharacteristics and accessibilityby car. At each area we took many photographsand notes on vegetationand physicalcharacteristics. We recordedthe age and sex of ploverswhenever possible although sometimes glaring, midday lighting or the largenumber of ploversencountered at one time made thistask impossi- ble. We attemptedto find some nestsor broodsin each area and described nestssimilarly to thoseon the coast. NancySpear conducted surveys of the breedingpopulations on four of the Channel Islands. On 25 and 26 April 1978 she searchedbeaches on San ClementeIsland and between19 and 21 May 1978, with Hal Spearand Bob Jackman, beacheson San NicolasIsland. From 13 to 18 July 1979 the Spearsand Mike Hill coveredmost of San Miguel Island'sbeaches, and on 22 July Bud Antonelissurveyed five additionalones. From 4 to 7 June 1980 the Spears surveyed beacheson the east end of Santa Rosa Island. On all surveysthey recordedthe numberand locationof all ploversand whenever possible,their age and sex. The historicalstatus of breedingSnowy Plovers throughout the statewas inferredfrom breeding records in the literature,from unpublished field notes, and from egg and nest collectionrecords and summarizedin Appendix 1. Sourcesof unpublishedrecords are listedin Appendix3.

RESULTS

I. CHANNEL ISLANDS NANCY L. SPEAR Basedon my surveys,at least 130 pairsof Snowy Ploversbreed on San Nicolas,San Migueland SantaRosa islands (Table 1). The speciesalso may breed on , althoughthe lack of nestrecords from earlierin the centurywhen the islandwas regularly visited by eggcollectors (Kill pers. comm.), as well as the low numberof wide sandybeaches, does not attest well to the species'presence there. The remainingislands probably are not used by breeding plovers. As the following accounts illustrate, habitat availabilityrather than human disturbanceappears to be the major factor limitingbreeding distribution on the Channel Islands. San ClernenteIsland. This 34 km long, narrow islandlies 69 km south- southwestof PointFermin. Sandy beaches, once reported as commonalong the westand north sides,now existonly on the north;beach areas to the south,once reportedly sandy, are now primarilycovered with rocks.The Navy maintainsa smallbase on the islandand infrequentlyconducts large- scalemaneuvers covering the islandand usingbeaches as entrypoints. Snowy Plovers probably do not breed on this island. Howell (1917) reporteda few birdsin fall 1907, but therehave been no reportsduring the breedingseason. I surveyed40% of the coastlineby foot and observedfrom a distanceanother 40%. I foundno SnowyPlovers, nor muchappropriate breedinghabitat. That habitatwhich did existis at NorthwestHarbor, a beach usedfor recreationalpurposes as well as for minormilitary maneuvers. Island Foxes (Urocyonlittoralis clementae) and Common Ravens (Coruuscorax) occurbut I doubt that their presenceis a major reasonfor the absenceof plovers. SNOWY PLOVER BREEDING STATUS

Santa Catalina Island. The 30 km long Santa Catalina Island is rugged, mountainousand hasprecipitous shores with few sandybeaches. It is heavily used by the public for boating and other recreation.Although Meadows (1934) reported Snowy Ploversas common on the beach at Howland's Landing, it is now generallyagreed that they do not breed regularlythere (Jones pers. comm.). San Nicolas Island. San Nicolas, the Channel Island farthest from the mainland, lies 98 km south-southwestof Point Mugu. It is 13 km long and 5 km wide. The Navy maintainsa basewith an airstripon the northeast side. Sandy beachesare common along the perimeter and are backed by dunes, bluffs and sandstonerock. Snowy Plovers are regular breeders; evidence dates back to the early 1900s when Willett (1912) found them "fairlycommon" and Howell (1917) reportedtheir breeding.Reports from 1976 and 1977 indicatedbreeding ac- tivity with Jones (pets.comm.)describing them as "a widespreadbreeder every year," and Schroeder (pets. comm.) reporting them to be common and breedingin 1977 on the five beacheshe surveyedmonthly for bird car- casses.On my 1978 surveyof 24 beaches,133 adult, 2 juvenileand 9 chick (4 broods)Snowy Ploverswere found. Adding estimatesfor three additional beachessurveyed by telescopefrom nearby bluffs, I estimate74 breeding pairs (Table 1). No scrapesor nestswere found mainlybecause there was lit- fie time to look for them. Althoughplovers were found around all the island,the heaviestconcentra- tionsoccurred on the northwestedge at Red Eye Beach, on the sandspitat the eastend, and from just west of Dutch Harbor to Daytona Beach. Com- petitionfor spacemay occuron southwestside beaches, which supportseal

Table 1. Numberof SnowyPlover pairs on the ChannelIslands. Sources are discussed in the text.

ESTIMATED ISLAND PAIRS From 1978 Survey San Clemente 0 San Nicolas 74 From 1979 Survey San Miguel 35 From 1980 Survey Santa Rosa 21 Estimates Based on Other Sources Santa Catalina 0 Santa Barbara 0 Anacapa 0 Santa Cruz --

TOTAL OBSERVED 130

4 SNOWY PLOVER BREEDING STATUS and sea lion rookeries.Although a few adultsand chickswere reportedon one of thesebeaches in 1977, we foundnone during the 1978 survey.Island Foxes,Common Ravensand fetal catsare presentbut not abundant,sug- gestinga low threatfrom predators. The birdsdid not appearto be disturbedby humanactivity, but increased navaloperations, with an expectedincrease in personnelare proposedfor the nearfuture. This almost certainly will increase beach use and breedingactivi- ty may be affected. Santa Barbaraand Anacapa Islands.Santa Barbaraand Anacapaare the smallestislands. Their shoresare bold and almostperpendicular. As there are no beaches,Snowy Ploverscannot breed on either island (pers. obs., Jones pers. comm.). Santa Cruz Island. Santa Cruz, the largestChannel Island, is 34 km long and is located 27 km west-southwest of Port Hueneme. Beaches around the islandare interspersedwith steepcliffs rising directly from the water; the largerbeaches are on the eastand westends. A dozenanchorages around the islandare heavilyused duringlate springand summerby cruising yachtsmen.Although access is by permit only and restrictedto hiking, beachesnear popularanchorages probably receive heavy use, whichcould deter Snowy Ploversfrom nesting. The Snowy Plover'sbreeding status on Santa Cruz is uncertain.Howell (1917) reportedthe birdsto be "fairlycommon during the latefall of 1907." Observersconducting bird carcasscensuses found a few SnowyPlovers us- ingeight beaches during August 1976 and fromJanuary to March1977, but none from April to June, suggestingthe specieswinters but doesnot breed on the island. SantaRosa Island. Lying 39 km southwestof GoletaPoint, SantaRosa is 24 km long and 16 km wide. Precipitousrocky shorelinesconstitute the northand southsides, while the eastand westcoasts consist of manysandy beaches. At least43 Snowy Ploversbreed there. Between March and September, 1968 to 1976, from 2 to 40 birds have been found on the island (Collins pers. comm.). During my survey,which includedall beachbetween Skunk and Eastpoints on the eastend of the island,43 adultand 2 juvenileSnowy Ploverswere found. It is highlyprobable that a similarnumber of ploversoc- cur on unsurveyedbeaches between Cluster and Sandy points on the southwest side of the island. Santa Rosa'sbeaches are privatelyowned and receivelittle human distur- bance. A potentialpredator on plover eggs and chicksis the Island Fox, whose tracks were found on most beaches. San l•iguel Island. The westernmost island of the northern group, San Miguellies 37 km southeastof PointConception. The shoresvary from bold, rockycliffs to stretchesof beach.Willett (1912) reportedSnowy Plovers there in summer. Recentobservers reported sightings in May and June 1977 and believedthe speciesprobably bred in restrictedlocalities every year (jones, Collinsand Kelly pers. comm.). During our 1979 survey84 adult, 8 juvenileand 4 chickSnowy Plovers• were found. As thisspecies begins autumn migration in July, all birdsseen were not necessarilybreeding on San Miguel.Most birds were found singly or SNOWY PLOVER BREEDING STATUS

in smallgroups but one flockof 10 may havebeen migrants and hencehave not been includedin the estimatedtotal of 35 breedingpairs (Table 1). Except for Cuyler Harbor, beaches on San Miguel suffer little human disturbance;however plans are currentlybeing considered to open the island to increasedpublic use. IslandFoxes are abundantand may destroysome nests.We found fairly fresh fox trackson most beaches.

II. MAINLAND COAST LYNNE E. STENZEL, SUSAN C. PEASLEE and GARY W. PAGE Survey CensusResults During the 1977 and 1978 breedingsurveys 954 adults,representing an estimated498 pairs of Snowy Plovers,were found on the mainlandcoast (Table2). They occurredin 45 locationsand in all but 4 eithernests or chicks were found. In the remainingfour areas, all in San Diego County, another observerfound nestsor chickseither later in the seasonor the followingyear. Breedingplovers were locatedin all coastalcounties except Los Angelesand San Francisco.Accounts for each county, startingat the Mexicanand ending at the Oregon border, follow. SAN DIEGO COUNTY, with 26% of the estimatedpairs on the coast, supportedthe mostbirds. We found breedingplovers on spitsand alkaliflats at the River mouth, on saltevaporators, bay fill and beachesaround San Diego Bay, on the northernlagoons, and on spitsand alkaliflats at the Santa MargaritaRiver mouth (Table 2). When surveyed, BatiquitosLagoon, flooded from winter and springrains, had only a narrow ring of potential habitat.Later, droppingwater levels exposed additional suitable nesting flats. A countof 39 adultsmade by otherslater in 1978 and, in otherrecent years, of 75 adults (Appendix 1), probably are more representativeof plover numbersat Batiquitosthan our count of 6 adults. Although we found no positiveevidence of breedingat the SweetwaterRiver mouth, Silver Strand bay shoreor BatiquitosLagoon, nestingat thesesites was confirmed later in 1978 by Parkeras well as by severalobservers in otheryears (Appendix1). We found three plovers,which showed no signsof nesting,at FrenchCreek mouth. No subsequentvisits were made that season,but in July 1979 Parker found a chickthere. At PenasquitosLagoon in 1978 he found four adultshe suspectedwere nestingand, in 1979, a pair with a nestwhere we had found no plovers in 1978. San Diego County has historicalrecords of breedingplovers for a number of coastalsites (Appendix 1). Imperial Beach and Coronado beachfronts, Ocean Beach, MissionBay beachfront,Pacific Beach, Del Mar Beach, and the Oceansidebeachfront, all former nestingsites, have beenso alteredin recentyears by development,erosion or humanuse, that habitatno longerexists for nestingSnowy Plovers. Conversely, a major breedingsite in the San DiegoBay area wascreated with the constructionof the Western Salt Works where a number of plovers nest undisturbedon levees. ORANGE COUNTY once supported substantialnumbers of nesting SnowyPlovers (Appendix 1) but duringour surveyheld only 2% of the pairs on the mainlandcoast; all were at the BolsaChica Oil Fields(Table 2). These SNOWY PLOVER BREEDING STATUS oil fields,on disusedsalt evaporators in BolsaChica Bay, offerrelatively un- disturbedalkali flats for nesting.Bay fill nearSunset Aquatic Park constitutes the onlyother recently used nesting area in OrangeCounty. Nests were col- lectedfrom beaches in OrangeCounty until 1940. By 1947 Cogswell(1947) notedthat formerlygood beachnesting habitat had deteriorateddue to in- creasedhuman use. Because of rakingand heavyhuman use, beach nesting habitatis no longer suitablefor Snowy Plovers.Beaches are now raked regularlyfrom NewportBay northto SunsetBeach. Newport Bay spitand SunsetBeach have some unraked, vegetatedportions of upper beach, but BolsaChica and Huntingtonstate beaches are completelyraked and denuded of vegetation.Although we found no ploversat the fenced-offLeast Tern nestingsite at the SantaAna Rivermouth on the southend of Huntington StateBeach, we suspectone or two ploverpairs could nest at thissmall, un- disturbed oasis. Although no ploverswere found during our survey, LOS ANGELES COUNTY oncesupported many breeding pairs. Records of nestson beaches adjacentto metropolitanLos Angeles,at Redondoand Ballona,are all prior to 1908 (Appendix 1), althougha plover incubatinga nest amid many human batherswas photographedon ManhattanBeach in 1947 (Cogswell 1947). In 1903 one eggcollector reported counting 50 pairsof ploversalong a 2 milestretch of beachbetween Ballona and SantaMonica (NMNH eggset 31481). In 1938 a set of eggswas collectedfrom a beachwhere six plover nestswere said to be present among those of Least Terns 8 km north of Malibu (WFVZ egg set 3497). We have been unable to find recordsof nestingon beachesin Los AngelesCounty since 1949, when one incubating adultwas reported from MalibuBeach (Stager 1949). The frequentraking of all countybeaches now precludesthe possibilityof Snowy Plovernesting. In VENTURA COUNTY beachesand river barsfrom Mugu Lagoonto the Santa Clara River mouth supported14% of the plover pairs on the coast. Sixtypercent of the Ventura Countybirds were found on the relativelyun- disturbedspits of Mugu Lagoon at Pt. Mugu Naval Air Stationwhich is off- limitsto the public. On Ormond Beach, adjacentto Mugu Lagoon and ex- tending northwestto Hueneme, ploverswere found on pond marginsthat are a continuationof the Mugu Lagoon .Except at Mugu Lagoon and McGrath State Beach, where we found the remainingSnowy Plovers, beachhabitat in Ventura Countyis mostlyraked, residentiallydeveloped or heavilydisturbed by off-roadvehicles. While recordsfrom museumegg col- lectionssuggest that ploversonce nested along most of the beachfrom Mugu Lagoonto the cityof Ventura, on our surveyplovers were absentfrom the mostdisturbed sections (Appendix 1). SANTA BARBARA COUNTY held the secondhighest number of coastal breedingSnowy Plovers,with 16% of the estimatedpairs. The moststriking changethat has occurredin thiscounty is the disappearanceof the species from breedinggrounds southeast of Point Conception(Appendix 1). At El Esterospits (Carpinteria and Sandyland),Santa Barbara Beach and Goleta, where at least 58 clutcheswere collectedbetween 1891 and 1948, we were unableto find suitablywide or untrampledbeach habitat(less than 100% coveredby human footprints).In 1927 one collectorcounted 24 pairsat Goleta (WFVZ egg set 31500) where we found no plovers on the small, 7 SNOWY PLOVER BREEDING STATUS

heavilyused public beach. On smailbeaches west of Goletawe found some suitablehabitat but no plovers.Apparently erosion of habitathas been a ma- jor factoreliminating Snowy Ploversfrom southeasternSanta BarbaraCoun- ty. We discoveredlarge numbersof ploverson the beachesand river mouths of northern Santa Barbara County, primarily on Vandenberg Air Force Base'sPurisima Point beach, which is off-limitsto the public. SAN LUIS OBISPO COUNTY, with 9% of the coastalbreeders, has only two large, potentialnesting areas, the northernsection of the Niporeo Dunes (extendingfrom the Santa Maria River north to PismoBeach) and Morro Bay spit (Table 2). At the Nipomo Dunesfew ploverswere found away from the SantaMaria River. Two nestsat PismoBeach in 1965 are the only previously reported nests on this section of the coast, which seemed to be suitable breedinghabitat. Heavy human use, includingintensive vehicle traffic, prob- ably resultsin the paucityof nestingplovers away from the Santa Maria River mouth. Plovers were dispersedalong the entire length of Morro Bay spit, which appearedto be lightlyused by humans.Documentation for nestingin the Morro Bay area extends back to 1926. MONTEREY COUNTY held 12% of the coast's and over two-thirds of MontereyBay's sizable Snowy Ploverpopulation. Plovers occurred primarily from Marina Beach to MossLanding's Western Salt Works. While increased human disturbancehas probablyreduced the number of ploversthat now breed on the accessiblebeaches north of the Salinas River mouth, the loss hasprobably been partiallycompensated for by the developmentof relatively undisturbednesting habitat at the Moss Landing salt evaporators.Where ploversonce nestedfrom PacificGrove to Marina Beach (Appendix 1), they no longer do so since high tides now wash to the base of high wave-cut dunes. SANTA CRUZ COUNTY supported5% of the coastalbreeding plovers, all in two locations(Table 2). At the PajaroRiver mouth ploversnested on the beach and on open alkali flats in a salt marsh behind the housing developmentnorth of the river. Wilder Beach, known as a nestingarea since 1922, held an unusuallyhigh number of ploversfor its small (0.5 km long) size.Egg recordsfrom Palm Beach and the mouthsof Moore, Four-Mile and Scott creeks indicatethat in the past other small pocket beacheson north supported nestingplovers (Appendix 1). In 1979 Vollmer (pers.comm.) found three adultsand a brood at the Laguna Creek mouth, and Metropulos(pers. comm.) found eightadults and at leasttwo broodsat the mouth of Waddell Creek. Apparentlythe speciesstill breeds sporadically on some of these publicly-usedpocket beaches. In SAN MATEO COUNTY, which supportedjust over 1% of the coastal birds, breedingSnowy Plovers were found on the little disturbedbeach at Afio Nuevo State Reserve and on the beach and sand flats at Pescadero Creek mouth. Nesting records from Afio Nuevo are very recent but Pescaderohas been a known nestingarea since 1927 (Appendix 1). The beachat FranklinPoint, just north of Afio Nuevo, where eggswere collected early in the century,has erodedto a narrowterrace backed by dunesperched on a 1-3 m high bank. At the time of our surveyit was an unsuitablenesting site. SNOWY PLOVER BREEDING STATUS

It is understandablethat the heavily eroded and intensivelyused beaches of SAN FRANCISCO COUNTY currently provide no habitat for nesting Snowy Plovers, but it is interestingthat no historicalrecords of breeding could be found. Probablythey nested on the dune-backedOcean Beach before urban development spread to the shoreline. The plovers found in MARIN COUNTY represented4% of the coastal population.All but one pair were found on the beachesof the Point Reyes National Seashore;the remaining pair was on the Bolinas Lagoon spit. Althoughthere appearedto be suitablehabitat at Dillon Beach, at the mouth of , no plovers were found. Historicalrecords in Marin County are limited to a single nest found on Point Reyes Beach in 1926 (Booth 1926) and a few unpublishedobservations of nestsor broodsat Limantour Esteroand BolinasLagoon by PRBO personnelin the 1970s. Beachesnear Bodega Bay in SONOMA COUNTY are only occasionally used by small numbersof nestingplovers. Although we found no plovers during the 1977 survey, a nest was found in late April on Creek Beach in 1978 (Appendix 1). The nest and incubatingadult disappeared within two days. Snowy Plovers probably bred regularly on the spit of BodegaHarbor but, sincethe area has been developedand becomeheavily used for recreation,breeding is now probablyirregular at best. MENDOCINO COUNTY'S share of the coastal population, 2%, was locatedon 7.4 km dune-backedMacKerricher Beach. We found no previous countybreeding records, but suspecta lack of observersis responsiblefor the absenceof previousrecords. HUMBOLDT COUNTY, with 6% of the coastalplovers, held more birds than any countynorth of MontereyBay. This undoubtedlywas related to the extensiveamount of potential habitat, consistingof 115 km of sand beach backedby dunesor wetlands(Anon. 1971). Recordsof nestingin the Hum- boldtBay area extendback to 1899 (Appendix1) but are lackingfor beaches to the north where we found breedingbirds (Table 2). Absenceof past recordsfor the northern area probablyis related to a lack of observers.We cannot explain the absenceof nestingSnowy Plovers south of Humboldt Bay, at the north and south spitsof the Eel River and at McNutt Beach. DEL NORTE COUNTY held just over 1% of the coastalpopulation with nestingbirds on the beachat Lake Talawa and the Smith River spit. Yocom and Harris (1975) suspectedbreeding in the Lake Talawa area but no definiterecords were reported until Widrig (pers.comm.) found them nesting there in May 1977. Lack of observercoverage is undoubtedlyresponsible for the paucityof historicalrecords for this county.

Coastal Habitat Coastalhabitats were grouped into six types: 1) bluff-backedbeach: beach backed by cliffs, bluffsor other non-dune, non-wetlandhabitat; 2) dune- backedbeach: may be interruptedby a river,creek, pond, lagoonor saltflat; 3) smallpocket beach: short beach at the mouthof a river, creekor lagoon anddelimited and dominatedby bluffsor rockypoints; 4) spit:a sandspit or bar separatingthe ocean from a coastalwetland; 5) estuarinemargin: disturbedor naturallyopen area in or at the marginof an estuaryor a lagoon (often a salt flat); 6) salt evaporator. SNOWY PLOVER BREEDING STATUS

Table2. Numbersof SnowyPlovers breeding in coastalCalifornia. San Diego County to SanMateo County from 1978 survey; Marin County to Del NorteCounty from 1977survey. Area types are explained in thecoastal habitat section of text.

Area Est. Total Known Known Juve- Type Pairs Adults Males Females niles Broods Nests San DiegoCounty 131 257 TijuanaR Mouth 4 19 37 16 8 1 1 1 4 3 5 1 2 1 SilverStrand Bay Shore 4 3 6 1 2 WesternSalt Works 6 16 31 12 12 1 3 2 Sweetwater R Mouth 5 9 18 3 6 SanElijo Lagoon 5 12 23 6 4 1 BatiquitosLagoon 5 3 6 3 AguaHedionda Lagoon 5 27 54 6 2 StaMargarita R Mouth 4 37 74 23 16 1 French,Aliso Cr Mouths 3 2 3 2 1 OrangeCounty 10 19 BolsaChica Oil Fields 5 10 19 8 8 2 Ventura County 71 136 MuguLagoon Spits 4 41 82 36 27 2 6 2 Ormond Beach 2 14 25 14 6 1 1 McGrath State Beach 2 3 4 2 1 1 2 Santa Clara R Mouth 2 13 25 12 5 1 1 Santa Barbara County 82 158 Santa Ynez R Mouth 2 5 10 1 1 2 Purisima Point Beach 2 55 109 30 38 2 6 6 So. NiporeoDunes 2 4 4 4 2 Santa Maria R Mouth 2 18 35 10 13 2 1 San LuisObispo County 43 86 No. NiporeoDunes 2 3 6 2 3 1 MorroBay Spit 4 40 80 24 27 13 4 5 MontereyCounty 60 115 Point Sur Beach 2 2 3 2 2 Marina Beach 2 12 23 8 9 1 SalinasR Spit 4 16 31 2 1 SalinasR State Beach 2 4 7 3 4 2 Western Salt Works 6 24 47 7 7 2 8 MossLndng.-Zmudowski 2 2 4 1 2 2 Santa Cruz County 25 50 PajaroR Spit 4 17 34 8 5 Wilder Cr Beach 3 8 16 5 6 3 San Mateo County 7 13 Afio Nuevo Beach 2 5 9 4 4 1 PescaderoCr Spit 4 2 4 2 2 1

10 SNOWY PLOVER BREEDING STATUS

Table 2 (Cont.)

Area Est. Total Known Known Jure- Type Pairs Adults Males Females niles Broods Nests Marin County 21 40 BolinasLagoon Spit 4 1 1 1 Limantour EsteroSpit 4 4 8 3 3 Drakes Beach Spit 4 1 2 1 1 Point Reyes Beach 2 15 29 12 9 Mendocino County 9 15 MacKerricher Beach 2 9 15 7 8 Humboldt County 32 54 So. HumboldtBay Spit 4 4 7 3 2 No. HumboldtBay Spit 4 6 11 5 5 Elk R Spit 4 I 1 1 Beach 2 2 3 1 2 Mad R Spit 4 10 17 9 7 Clam Beach 2 1 2 1 1 Big Lagoon Bar 4 8 13 4 8 1 Del Norte County 7 11 Lake Talawa Beach 2 3 5 2 2 1 Smith R Spit 4 4 6 2 4 2

TOTALS 498 954 287 275 25 57 72

Smallpocket beaches are sometimes similar to spitsbut are distinguished byseveral characteristics. Because pocket beaches are short and usually span lessthan 1.5 kmof coastline, they are almost always dominated by alelimiting cliffsor bluffs.Significant vegetated dune or hummockdevelopment behind the beachis usuallylacking. Spits may be delimitedat eitherend by cliffs, bluffs,dunes or lowlandsbut, becauseof theirlength and the presenceof fairlyextensive low wetlands behind them, they are not dominated by tower- ingtopographic features. They usuallyhave well developed dune or hum- mock structures between the beach and the . The six habitatsdiffered in importanceto nestingSnowy Plovers. The habitattype for eacharea supporting plovers on thesurvey is designated in Table 2. Noneof the manybluff-backed beaches surveyed held nesting Snowy Plovers;most were low and narrow, offering little habitat free from periodic tidalinundation. One exception, the privately owned isolated 5.8 km McNutt Beachin HumboldtCounty, was backed by a stretchof upperbeach over 100 m wideabove the hightide linebut, likeother bluff-backed beaches, heldno plovers.No obviousreason for their absence there was apparent. Dune-backedbeaches supported 34% of thepairs on the coast; all except PointSur, DillonBeach and Lanphere Beach were interrupted at leastonce by rivermouths, creek mouths, ponds or lagoons.Although these wetlands

11 SNOWY PLOVER BREEDING STATUS spanned only 7% of the 112 km of dune-backedbeaches that supported plovers,46% of the 170 pairs on thesebeaches were near these wetlands. Densitiesof ploversalong dune-backedbeaches were not particularlyhigh comparedto thosealong spitsexcept at PurisimaPoint and Afio Nuevo State Reserve (Table :3). Small pocket beachesproved to be generallypoor nestinglocations, col- lectivelyholding only 2% of the estimatedpairs; we found ploverson only 2 of 25 with potentialnesting habitat. At one of these, FrenchCreek mouth on Camp Pendleton,we found three adultsthat showedno signsof nesting. The other site, Wilder Beach, Santa Cruz County, was unusualamong small pocketbeaches, having a smallbut well developedterrace of vegetatedsand hummockson its upper beach. French and Wilder creek mouthsshare two importantcharacteristics: both are off-limitsto the publicand both are near other major nesting areas; French Creek is :3.4 km north of the Santa MargaritaRiver mouth and Wilder Creek is on the north side of Monterey Bay. Other Santa Cruz County pocket beachesoccasionally hold plovers suchas in 1979 when nestingbirds were found at Lagunaand Waddell creek mouths.Usually, however, small pocket beaches provide the only beaches alonglong stretchesof bluff-backedcoast, are consequentlyheavily trampled by bathers,and thereforeare difficultplaces for ploversto nestsafely. Some of the highestdensities of ploverswere on spits(Table :3). Sand spit habitat, which held 43% of the pairs along the coast, was undoubtedly enhancedby the fairly extensivebordering wetlands. Tidal flats and other open areas in marshesafforded alternate, often productivefeeding areas, and a refugefrom human disturbanceon the beaches.At the TijuanaRiver, Santa MargaritaRiver, Mugu Lagoon and spits,salt pans in ad- jacent marsheswere also usedfor nesting.Snowy Ploversoften were seen moving between salt pans, tidal flats, and beaches,indicating these areas function together in providing habitat. Supplemental feeding and nesting areasprovided by wetlandsand saltflats caused plover densities(measured along the length of the spits)to be higherthan they might otherwisehave been. For example,spits at the TijuanaRiver and nearbySilver Strand beach in San Diego County both receiveheavy human use. However, the spit at the Tijuana River adjoins a salt marsh with extensivesalt flats which the ploversuse, while Silver Strandbeach is separatedfrom the few remaining undevelopedportions of the bay shoreby a major roadway.The densityof ploversalong the Silver Strandspit was lessthan a tenth that along the Ti- juana River spitsand was noticablylower than that on other spits(Table :3). Spitsthat supportednesting plovers varied in topography,vegetation and compositionof the adjacentwetlands. South of Point Conception,Santa Barbara County, most spitswere coveredby low, vegetatedmounds, but to the north they were often coveredby extensivevegetated dunes, sometimes over :30 m high. Open areasaround , which held 12% of the coastalpairs, include lagoonmargins, disturbed areas (saltpans) in saltmarshes, and bay fill. All of theseareas were usuallylevel, with topographicrelief exceeding 50 cm only at San DiegoBay fill sites,which were 2 to :3m abovethe bay margin,and at Bolsa Chica Oil Fields, where roadwayswere built 2 m above the marsh. Substratewas alwaysat leastlightly compacted and debrisusually covered

12 SNOWY PLOVER BREEDING STATUS

lessthan 1% of thearea. Marsh salt pan also occurred behind the spits at the Tijuanaand Pajaro river mouths, at MuguLagoon and at theMoss Landing Salt Worksbut, becausesalt pans functioned as part of a broaderhabitat systemat theseareas, they are consideredas subareasof the spitsor salt worksrather than separatelyas open areasin estuaries. Saltevaporators, which supported 8% of the pairson the coast,afforded Snowy Ploversa man-madehabitat at estuaries.Plovers nested on low dikes separatingevaporator ponds and on floorsof driedevaporators. They fed on theabundant brine flies (Ephydridae) at pondmargins. Dikes varied in height fromless than 1 m to 2 m abovethe watersurface. We foundmost plovers on unvegetatedportions of the lower dikes, except where Western Gulls (Larus occidentalis),Caspian Terns ($terna caspia), Forster'sTerns ($. forsterOor BlackSkimmers (Rynchops niger) were nesting. In generalthe densityof nestingplovers decreased from southto north (Table4), indicatingthat when human disturbance was not overwhelming, southernrather than northernbeaches provided the besthabitat.

Table3. Densitiesof SnowyPlover pairs estimated from census totals in Mayand June1978 in fourof sixhabitat types surveyed in southernand centralCalifornia.

Kilometers Hectares Pairsper of Coastline'of OpenArea Km or Ha Small Pocket Beaches FrenchCr Mouth 0.5 4.0 WilderCr Beach 0.5 16.0 Dune-backed Beaches Ormondto Ventura Beach 12.5 1.9 Santa Ynez R Beach 2.3 2.2 PurisimaPoint Beach 9.2 6.0 Nipomo Dunes Beach 20.9 1.2 Point Sur Beach 0.9 2.2 Marina Beach 5.6 2.1 SalinasR to PajaroR 10.1 0.6 Afio Nuevo State Reserve 1.1 4.6 Spits TijuanaR Mouth 3.7 (15) 5.1 SilverStrand 13.4 0.4 SantaMargarita R Mouth 1.9 (52) 19.5 MuguLagoon Spits 8.6 (12) 4.8 Morro Bay Spit 8.0 5.0 SalinasR Spit 2.0 8.0 PajaroR Spit 2.6 (3) 6.5 PescaderoCr Spit 1.0 2.0 EstuarineMargins SweetwaterR Mouth 17.5 0.5 San ElijoLagoon 63 0.2 BatiquitosLagoon 1.5 2.0 Agua Hedionda Lagoon 20 1.4 BolsaChica Oil Fields 68 0.1

'Does not includeriprapped, urban developed or bluff-backedshoreline.

13 SNOWY PLOVER BREEDING STATUS

Table4. Densitiesof SnowyPlovers along sand beaches in coastalCalifornia counties. Lengthsof sand beachin each countyfrom Anon. (1971).

Estimated Pairs on Estimated Estimated Estimated Kilometers Beaches& Pairsper Pairs in Pairsper of Sand Associated Kilometer Coastal Kilometer County Beach Flats't' of Beach't Habitatõ of Beachõ

San Diego 36.7 73 2.0 131 3.6 Orange 41.4 0 0.0 10 0.2 LosAngeles 70.8 0 0.0 0 0.0 Ventura 29.0 71 2.4 71 2.4 Santa Barbara 27.7 82 3.0 82 3.0 SanLuis Obispo 41.7 43 1.0 43 1.0 Monterey 33.5 36 1.1 60 1.8 Santa Cruz 19.6 25 1.3 25 1.3 San Mateo 12.4 7 0.6 7 0.6 San Francisco 4.0 0 0.0 0 0.0 Marin 35.1 21 0.6 21 0.6 Sonoma 17.4 1 0.1 1 0.1 Mendocino 12.4 9 0.7 9 0.7 Humboldt 115.4 32 0.3 32 0.3 Del Norte 19.8 7 0.4 7 0.4

Omitsbirds at saltworks, oil fieldsand northernSan DiegoCounty coastal lagoons. Includesall estimatedpairs from alongthe coast.

Generallynests were locatedin flat openareas devoid of, or sparsely coveredwith, vegetationor driftwood.On beachesin particular,nests were oftenplaced next to someobject such as a pieceof driftwood,kelp or plastic. Siteswere usually within 100 m of waterbut occasionally were several hun- dredmeters away when there was not a formidablebarrier of vegetationbe- tween the nest and the water. The absenceof sucha barrieris probablyim- portantso thatnewly-hatched chicks may have easy access to the shore. Broodsgenerally were located feeding near water, but when disturbed would retreatto the upperbeach where the chickswould crouch by driftwoodor run into vegetationto avoid beingseen.

Disturbance to Coastal Habitat Severalfactors affect the qualityof breedinghabitat. Humans have a con- siderableimpact through their recreational activities and by physically altering areaswith residential, industrial and recreationaldevelopment. Other agents of disturbanceidentified in otherstudies (Page unpubl. data) are highwinds, high water levelsand nestpredators. 14 SNOWY PLOVER BREEDING STATUS

The intensityand type of human activityvaried considerablyamong sites. Some activitiesprecluded the useof beachesfor nesting.In all of Los Angeles County and partsof Orange County, entire beachesare groomedwith large rakeswith tines 5 to 8 cm apart. These rakes are draggedbehind motorized vehiclesfrom the waterlineto pavement or the low retainingwall bordering the beaches.Since this is done once a week or more often, no nestcould sur- vive even if human use were not as intensive as it is. Other activities, such as the drivingof publicoff-road and militaryall-terrain vehicles, while causing considerabledisturbance and sometimesnest destruction,do not alwayspre- vent ploversfrom nesting. To measurethe effectof human activityon the densityof nestingplovers we had hoped to find physicallysimilar segments of coastlinethat received different intensitiesof human use. We found only one place where reasonablysimilar areas could be compared. In Santa Barbaraand San Luis Obispo countiesthere are two fairly long neighboringstretches of dune- backed beach, the dunes north of Purisima Point on Vandenberg Air Force Base and the vast Nipomo Dunes System (Santa Maria River dunes)farther north. They differ primarily in the extent of associatedwetlands; Purisima Point dunesare interruptedby one creek mouth and the Nipomo Dunes by a river and two creeks. However, the human use that these beachesreceive is quite dissimilar,with the Purisima area receiving almost none and the Nipomoarea receivinga lot, includingextensive off-road vehicle traffic. The densityof nestingplovers along Nipomo Dunes beach is lessthan a fifth of that along PurisimaPoint beach, despitethe fact that the Nipomo systemhas more wetland habitat.In addition,nesting plovers are dispersedalong much of the Purisimacoast, whereas 78% of the ploverson Nipomo Dunesbeach were concentratedaround the mouth of the Santa Maria River. Although a more thoroughpopulation and habitatstudy would be necessaryto assess the causesof thesedisparate densities, they do suggestthat human activities can severelydepress the number of nestingplovers. The introduction of Marram Grass (Ammophila arenaria) to stabilize coastaldunes has alteredthe physicalstructure of beachesand has almost certainlydetrimentally affected nesting Snowy Plovers.We found Marram Grassfrom Ventura County north; it was well establishedin many areas north of Point Conception.The formationof the foredune parallelto the shorelinetypically built by the sand-bindingroots of MarramGrass decreases open, unvegetatedareas above the tidelinesand thereforethe amount of potentialnesting habitat. Vegetated dunes of beachesdominated by the nativedunegrass (Elymus mollis) are usuallyperpendicular to the shoreline and are oftenseparated by expansesof fairlyflat sandthat extendback from the upperbeach and are favoredplover nesting sites. Barbour et al. (1976) foundthat Ammophila-dominated beach held about half the numberof plant species,had lessopen area and had steeperslopes than adjacentbeach dominatedby Elymus. Slobodchikoffand Doyen (1977) found that Am- mophilamarkedly depressed the abundanceand diversityof sanddune ar- thropodsin California.Since Snowy Plovers often feed on insectswell above the high tide line, their food supplymay be detrimentallyaffected by the presenceof Ammophila.The PipingPlover (Charadriusmelodus), a bird

15 SNOWY PLOVER BREEDING STATUS

with similar habits, declined in numbers on a New York State beach after Ammophila was planted in its nestingarea (Wilcox 1959). Among non-humanrelated factors, predators, which on the coastappear to be mainlycorvids, are knownto have a markedeffect on plovernesting success(Page unpubl. data and Wilsonpers. comm.). Ravenswere seenat only 6 and crowsat 4 of 107 sitessurveyed south of the Golden Gate. This spottycorvid distributioncontrasts with the north coast, where ravens were seen on 34 and crowsat 10 of the 41 sitessurveyed. We believethat nesting ploverssouth of the Golden Gate may sufferless from corvidnest predation than those to the north. Strongwinds and high water are the other factorsaffecting breeding suc- cess.At Pajaro Dunes, Santa Cruz County, strongwinds were found to be a major causeof nest loss (Warrinerand Warriner unpubl. data). Extremely high tides, especiallyspring tides in June and July, washed away nestsat Limantourspit, Marin County (Pageunpubl. data). Egg collectorsnoted that hightides washed away a nestin San Diego County (WFVZ eggset 91,240) and nearlyinundated one in Santa BarbaraCounty (CMNH egg set 1192). Althoughit is impossibleto reach any valid conclusionabout the effect of high winds on Snowy Ploversduring this survey, we can comment on the probableeffects of high water. The winter of 1977-78 was unusuallystormy and high wavesseverely eroded beachesin southernand centralCalifornia. By early May, when we startedthe surveyof the south coast, many eroded beacheshad not yet recoveredtheir normal sand loads. One employeeat SilverStrand State Beach, San Diego County, told us that 45 m of the nor- mal 100 to 130 m of beachwidth had been removedby stormsthe previous winter. We also found that several coastal lagoons, whose level sandy marginspreviously provided nesting habitat, were floodedby winterrains up to the vegetatededges or steepbanks and thereforelacked suitable breeding habitatat that time. Later in the seasonwater levelsdropped in mostlagoons, whichthen were usedby nestingplovers. Because much of the floodedand eroded coastalhabitat eventually was restored,nesting areas appeared or in- creasedin sizein some locationsafter our survey. These habitatalterations undoubtedlywere responsiblefor some shiftingof nestingbirds between locationsduring the summer.

III. AND THE INTERIOR R. PHILIP HENDERSON and GARY W. PAGE ,SanFrancisco Bay Having habitataffinities with the interiorand beingsomewhat isolated from the open coast,San FranciscoBay falls into an intermediatecategory be- tween the coastand the interiorand thereforeis consideredseparately. Dur- ing the survey351 adultplovers were found in the bay with 90.6% of these in COUNTY, 5.4% in SAN MATEO COUNTY• and 4.0% in SANTA CLARA COUNTY (Table 5); they occurred at functioningand abandonedsalt evaporatorssouth of the San Mateo Bridge. The majority were on the east side of the bay, on leveessurrounding evaporators brim- ming with water and on levees and flats in partly dry evaporators.Their 16 SNOWY PLOVER BREEDING STATUS distributionon levees was patchy and their absencefrom some was inex- plicable, although when found, birds were almost always on levees separatingone evaporatorfrom another and seldom on leveesseparating evaporatorsfrom the bay or the land. Nestswere locatedon leveesaround filled or partly dry evaporatorsor on dry flats in partly empty or disused evaporators. Snowy Ploversbred at saltevaporators in South San FranciscoBay as ear- ly as 1918; Grinnell et al. (1918) noted that "a great many pairs nestedon dikesseparating salt ponds on the east side of the bay, at the Alvaratio salt works, and that workmen had reported having broken many eggs with wheelbarrows," As one nest was collected 15 May 1919 on a levee near RedwoodCity, they alsonested on the westside of the bay earlyin thiscen- tury. Subsequentscattered breeding records at the Haywardsalt ponds, near the Dumbarton Bridge, near Alvisoand near Belmont are summarizedin Ap- pendix 1; we found birdsin all theseareas. We found none on sandfill at the end of the main runway at Oakland InternationalAirport where Manoils (pers. comm.) found a few adultsin 1977, and Feeney (pers. comm.) saw five adults in 1979, nor did we have any reportsof breedingon the south shoreof Alameda where there have been occasionalrecent records (Appen- dix 1). In summer, 1971, during an extensive survey of the breeding birds of South San FranciscoBay, Gill (1972) found 15 Snowy Plover nestsat two locations,on the Knapp Gun Club property 4 km northwestof Alviso, and on levees at the east end of the Dumbarton Bridge. He concluded that "breedingpopulations of SnowyPlovers within the studyarea wouldapprox- imate . . . 150 pairs. This would include nestingactually observedduring 1971 plusobservation of other adultbirds within the majornesting areas and sightingsof additionalbirds in areaswith suitablenesting habitat such as , Moffett Field, and the Drawbridge-CoyoteCreek areas." We found ploversbreeding in both areas where Gill found them breeding but at one, the Knapp Gun Club property, they were much lessnumerous duringour survey.At Bair Island,the Moffett Field area and the Drawbridge- Coyote Creek area where Gill found birds but no nests, we found neither nestsnor birds.At mostonly 199 of the ploverswe countedwere withinthe area Gill estimatedheld 150 pairsin 1971. Becauseof the patchinessof the plovers' distribution in South San Francisco Bay, Gill may have overestimated numbers, so that the two sets of data should not be construed as indicatinga decline. At best the data indicatethat sinceat least 1971 the man-made salt evaporatorsof South San FranciscoBay have been one of the most important breeding areas in the state. AlthoughGill (pers.comm.) foundthree pairsnesting on a saltevaporator levee in July 1975 at Little Island, NAPA COUNTY, our searchof this and many other levees in North San FranciscoBay failed to turn up a single Snowy Plover in 1978. The levee at Little Island was covered with 600 nesting Caspian Terns, several hundred roosting California Gulls (Larus californicus)and 80 roostingWhite Pelicans(Pelecanus erythrorhynchos). Sincethis crowdedlevee seemedto be the only suitablenesting area, we believethat the breedingof smallnumbers of ploversat salt evaporatorsin North San FranciscoBay is probablyirregular. 17 SNOWY PLOVER BREEDING STATUS

Table 5. Number of Snowy Ploversin San FranciscoBay during June 1978 survey.

Total Known Known Adults Males Females Juveniles Broods Nests

San Mateo County 19 10 2 2 3 Santa Clara County 14 7 4 3 2 1 Alameda County 318 85 83 3 50 35

TOTALS 351 102 89 8 55 36

Table 6. Numbersof Snowy Ploversfound in 1978 in the Californiainterior. Asterisks(') indicatefirst reportedbreeding records.

Total Known Known Adults Males Females Juveniles Broods Nests

Imperial County 216 216 78 82 7 10 Riverside County 10 Salton Sea 10 1 4 San Bernardino County 77 Harper Lake 61 14 8 1 1 ' Seaties Lake 16 4 4 2 9 Kern County 34 Rosamond Lake 6 4 2 ' Koehn Lake 26 10 8 2 1 Goose Lake 2 1 Kings County 1 Corcoran Reservoir 1 1 Inyo County 522 ' Tecopa Marsh 7 4 3 1 Owens Lake 499 115 81 4 35 21 Salt Lake 1 1 ' Tinemaha Reservoir 2 1 1 1 Deep SpringsLake 13 6 5 3 Mona County 384 Mono Lake 384 181 139 31 Lassen County 208 ' Honey Lake 208 81 33 28 20 4 Modoc County 391 ' Lower Alkali Lake 92 22 11 8 11 10 ' Middle Alkali Lake 36 13 3 13 5 ' Upper Alkali Lake 230 45 38 51 42 11 Goose Lake 33 18 8 4 11

TOTALS 1843 597 433 110 147 90

18 SNOWY PLOVER BREEDING STATUS

The Interior Duringthe 1978 surveywe found1843 adultSnowy Plovers at 18 interior locations;nests or chickswere found at all except4 (Table6). At 2 of those4 locations,Rosamond Lake and GooseLake in Kern County, the presenceof suitablenesting habitat suggested probable breeding. The male to female ratio was unbalancedat 10 males to 8 females, prob- ablybecause females incubate for mostof the daylighthours and were more difficult to find on their scatterednests than males, which concentratedat feedingplaces by water. Unfavorablelighting conditions or largenumbers of birdsoften preventedus from determiningthe sex of somebirds. Because of these factors, we have used the total number of adults rather than the estimatednumber of pairs as a measureof populationsize in the interior. The Salton Sea in IMPERIAL and RIVERSIDE COUNTIES accounted for 12.3% of the adultsfound in the interior. This percentagemight have been slightlyhigher had we not accidentallyomitted the LupineWash area in Im- perialCounty. Of the 226 adultsfound, 96% were in IMPERIAL COUNTY and 4% were in RIVERSIDE COUNTY. Althoughthey occurredaround the entire Salton Sea perimeter, the major concentrationswere on the west side from Desert Shores to the north half of the Salton Sea Naval Test Base and at the mouthof San FelipeCreek, and on the eastside from BombayCreek to the Wister Unit of Imperial Wildlife Area and on beachessouth of the Wister Unit. They occurredalong open, gentlysloping shorelines and in the region of washes. A few were found on fiats inside diked reservoirs but none on diked or denselyvegetated shoreline. Although most plovers were locatedin areas with little human disturbance,some were found between Desert Shores and SaltonCity, at DesertBeach and at BombayBeach, three areas heavily used by people. The Salton Sea formed from 1905 to 1907 when structural flaws in a canal systemallowed water from the Colorado River to flow uncheckedinto the Whitewater River Basin. Since then agriculturalrunoff has maintainedand even causeda risein water levels.We found no informationsuggesting that Snowy Ploversbred in the WhitewaterRiver Basin prior to 1905; a nest taken in 1929 is the earliestknown breedingrecord. This and other reports (Appendix1) indicatethat Snowy Plovershave been breedingat the Salton Seafor at least50 years.Our surveyresults indicate that it is currentlyone of the most importantbreeding sites in the state (Table 6). The only otherknown breeding location in RIVERSIDECOUNTY is Lake Elsinore.Records date from a nestfound in 1939 to the sightingof three "juveniles"(possibly chicks?) in April 1974 (Appendix1). At the time of our 1978 surveyhigh lake levels flooded into surrounding vegetation, leaving no suitablehabitat for nestingplovers and none were found. SAN BERNARDINO COUNTY held 4.2% of the interiorplover popula- tion at two sites,Harper and Searleslakes. Harper Lake, an alkali sink with somemarsh and open standingwater, accountedfor 79.2% of the ploversin the county.They were found on the southwestmargin of the lakebedin three separateareas with 37 birdsat the central, 15 at the southeast,and 9 at the northwesternmostsite. Sincewater is pumpedto at leasttwo of theseareas afterit hasbeen used for irrigationin nearbyalfalfa fields, the birds'habitat is

19 SNOWY PLOVER BREEDING STATUS largelyunder human control. Snowy Plovers were first known to be breeding at Harper Lake in 1977 when Hendersonfound at least67 adults,3 broods and one nest. The lack of earlierrecords is probablydue to the absenceof observers. The first reported breedingrecord at Searles Lake occurredduring our 1978 surveywith the discoveryof 16 adultsand 9 broods.Since all birds were feedingaround standing water leakingfrom a pipe at the westfacility of the Kerr-McGeeChemical Corporation plant, ploverbreeding at thisheavily industrializedlocation may have been unusual. The only other standing water on the alkali lakebed was a concentrated brine solution in solar evaporationponds and an effluent smellingof sulfur from the chemical plants. Three locations,Rosamond Lake, Koehn Lake and Goose Lake in KERN COUNTY, collectivelyheld 1.8% of the interiorpopulation. Although Rosa- mondLake is usuallydry, 25% of the lakebedwas flooded by fresh-tasting, silt-ladenwater when surveyed.On the unvegetatedeast shoreline the six ploversseen were believedto be breedingalthough no nestsor broodswere found. Two small bodiesof water lay on the otherwisedry alkali flatsat Koehn Lake. By the larger,25 ha body on the westedge of the lakebed,25 adults,2 broodsand 1 nestwere found. One additionaladult was seen by a 5 ha body of water near the old Saltdalesaltworks. At Koehn Lake strong windshampered surveying so that our populationestimate is probablylow. We foundno previoussummer records for eitherKoehn or Rosamondlakes. Agriculturalpractices have changed the landscapeof the Sacramentoand San Joaquinvalleys considerably during past decades.Most alkalinelakes whichprovided good nesting habitat have disappeared. The onlysuch areas we found were in the San Joaquin Valley on the Kern l•lationalWildlife Refugeand at GooseLake in KERN COUNTY. The onlyplovers found were two birds believedto be nestingat Goose Lake and a probablemigrant at CorcoranReservoir, and an area lackingsuitable breeding habitat, in KINGS COUNTY. Historicallythe SacramentoValley probablywas not a major nestingarea and we thereforeomitted it from the survey.The only three documented breedingrecords were an adult with youngat both the WoodlandSewage Pondsand the DavisSewage Ponds in YOLO COUNTY, and a nestthat was collectedin 1913 near Reigo in BUTTE COUNTY (Appendix 1). Historicallythe San JoaquinValley was probablymore importantas a breeding area than the SacramentoValley. There are several breeding recordsfrom near Los Banos in MERCED COUNTY (Appendix 1); one that wasparticularly well documented(Unglish 1938), notesthat 5 milesnorth of LosBanos a 5 acrepond with a few smallislands held 11 SnowyPlovers and at least4 nestsin 1937. It wasthe firsttime Unglish"in fifteenyears of field workin the LosBanos area" and onlythe secondtime hiscompanion Tyler, "in forty yearsin this section,"had ever recordedSnowy Plovers.Dawson (1923) mentionsthat plovers were breedingnear Los Banos as early as 1912. Other recordsfor the San JoaquinValley includea pair that was "probablypreparing to nest"just eastof Firebaughin MADERA COUNTY (Tyler 1916) and recordsfrom BuenaVista Lake in KERN COUNTY. Judg- ingfrom the accountsof Linton (1908) and Lamb and Howell (1913) signill-

2O SNOWY PLOVER BREEDING STATUS cant numbersmay have once bred at Buena Vista Lake. Both accounts report ploversin June, and Linton reporteda two egg clutchon 2 June 1907. Linton'sdescription of the lake indicatedideal breeding habitat. Today Snowy Ploversrarely breed in the San JoaquinValley. INYO COUNTY held the largestnumber of ploverswith 28.3% of the in- teriorpopulation. At Tecopa Marsh, where the meanderingAmargosa River createdsome marsh and open standingwater on an old lakebed,Henderson found seven adults and one brood of chicksfor the first definite breeding record. However, the specieswas reported in small numbersduring past breedingseasons by Tarble (pers.comm.); the highestnumber she saw was 12 birdson 18 June 1975. Undoubtedlysome were breeding. Owens Lake, with 499 birds, held more Snowy Ploversthan any other locationin the state.While we were there, waterfrom Cartago,Ash, Cotton- wood and Carroll creeksbypassed the Los AngelesAqueduct and flowed onto the alkalinelakebed where it formed a shallowbody of water on the west side. Water also seeped onto the lakebed at several locationsat its north, southand eastsides. Most birdswere found around water, especially alongcreeks, at creekmouths and at seeps.Ponds adjacent to the southend of the lake also held some plovers. Areas we were able to reach along the marginsof the mainbody of the lakeheld no birdsexcept near creek mouths. Most nests were found on the west side but broods were found almost everywherewhere adultswere near water. At Owens Lake in 1891 Fisher (1893) found the Snowy Plover "near Keeler, May 30 to June 4, where it was common in small flocks of five to ten on the alkaline flats which border the lake." He believed"the specieswas evidentlybreeding at the time, but no eggsor young were found." The only publishedinformation we found verifyingnesting at OwensLake was Heindel'sobservation in July 1975 of 130 adult-sizedplovers accompanied by downy youngat Dirty Socks(Mc- Caskie 1975) at the south end of the lake. Although Henderson found one Snowy Plover at Salt Lake in Saline Valley in May 1978 and two in June 1977, he found no evidence of breeding. Since the birds may have been transientsor summeringnon- breedersand sincethere are no past breedingrecords, the ploversbreeding status at Salt Lake remains uncertain. A pair of nestingplovers found by Hendersonin June 1978 at the Los AngelesDepartment of Water and Power'sfreshwater Tinemaha Reservoir representsthe firstbreeding record for thislocation. An employeeof LADWP indicatedthe flat on whichthe plover nestedwould soonbe floodedby rising water so the nestmay have beendestroyed; normally the area may not be a nesting site. The final INYO COUNTY sitewith Snowy Ploverswas the alkalineDeep SpringsLake, where 13 adultsand 3 broodswere found, mostlynear a small seep on the northwestmargin of the lakebed. LeValley (pers. comm.) reportedseeing about 30 ploverson the lakeon 29 and 30 May 1971, a time when migrantsshould have been absent.Two nestsfound in 1964 (Mc- Caskieand Pugh 1964) are the only previousnesting records. Mono Lake accounted for 20.8% of the adults in the interior and all of the SnowyPlovers in MONO COUNTY. The lake's384 birdsrepresented the state'ssecond largest concentration. Birds were found from Navy Beachon 21 SNOWY PLOVER BREEDING STATUS

the south side counterclockwisealong the shorelineto Black Point on the north side. A small,isolated pocket of birdsalso occurred at Mono County Park on the northwestside of the lake. Nestswere on unvegetatedgravel and sandridges up to 1.5 km from waterand on dry alkalifiats as closeas 100 m to the recedingwater line. In all, 128 nestswere locatedin 1978 (Pageet al. 1979). No one reportednesting Snowy Hovers at Mono Lake before 1976 when Winklet et al. (1977) found 3 nests,at least6 broodsand, on 14 September, had a highcount of 100 adult-sizedbirds on a censusof the entirelake. Page and Peasleevisited the area for 2 days in mid-June 1977 and found 90 adultsand 8 nestsalong part of the shoreline. Snowy Hovers occurredat one locationin LASSEN COUNTY, Honey Lake, where 208 birds made up 11.3% of those in the interior. Most birds were found along the southeastside of the lake from just southof Wende] to the baseof a broad peninsulathat bisectsthe southshore, alongthe westside of that peninsula,and along the north shore of the lake, especiallyin the vicinityof HartsonReservoir. Because we did not coverthe shorelinefrom 3 km eastof HartsonReservoir to 0.8 km southof Wendel, we may have missed some birds. The only nestsfounds were in clumpsof DistichIlsnear Hartson Reservoir but we suspectbirds also nested on dried, cracked mud several hundred meters from water on the east side of the lake. We found broods in all areaswhere there were adults.Prior to our surveythe only recordfor the Honey Lake area was an observationof two pairs on the floor of Hartson Reservoiron 11 June 1977 {Gainesfide Jurek pers. comm.). Four sites,Lower Alkali Lake, Middle Alkali Lake, Upper Alkali Lake and Goose Lake, in MODOC COUNTY held 391 birds or 21.2% of those in the interior. By the time we reachedthis area in early July the alkali lakeshad evaporatedconsiderably, exposing wide expansesof lakebed. On Lower Alkali Lake, where water coveredabout 50 % of the lakebed,all ploverswere found at the northeastend where open standingwater abutteda marsh.Ten nests were found in the same area but several hundred meters from the water on a low plateau borderingthe lakebed.Middle Alkali Lake was nearly dry but we found someplovers with broodsby open wateradjoining marsh near the north end of the lakebed. Ploverswere found along the eastside of Up- per Alkali Lake where 75% of the lakebedwas stillcovered by water; there was no suitableopen habitat on the west side. Some nestsat Upper Alkali Lake were near the edge of the lakebedon alkali flat as far as 2-3 km from water; other nestswere much closerto water. Broods were found by water mostlyat the northeastend of the lake.Ours are the firstbreeding records for all of the Alkali Lakes. The 33 adults and 11 broods near water on alkali flats at the southwest end of Goose Lake, MODOC COUNTY, were the lastplovers we found on the interior survey. Dawson (1923) reported breedingplovers here in June 1912, providingthe only other record. Since there was a breedingrecord in the Tule-Lower Klamath Lakes regionof SlSKIYOU COUNTY in 1957 (Gilesand Crabb1958), we visited thisarea but found no plovers.It is unlikelythat the speciesbreeds regularly there, exceptperhaps at White Lake justacross the borderin Oregonwhere we saw a few plovers. James Hainline, a biologistat Klamath Lake National 22 SNOWY PLOVER BREEDING STATUS

Wildlife Refuge, told us he had seen 8 adultsand 5 chicksat White Lake a few daysbefore our visitin earlyJuly but that he had not seenSnowy Plovers on the Californiaside of the refuge.

Inland Habitat Breeding habitat consistedprimarily of shallow lakes bordered by unvegetatedor sparselyvegetated flats. Inhabited lakes were distributedover the lengthof the state,mainly in the Upper and Lower SonoranLife Zones (Grinnell 1915); most were alkaline. Nestswere generally located in flat, openareas, although many were part- ly concealedby microhabitatfeatures. Of 45 nestsat the SaltonSea, Owens Lake, Honey Lake and the Alkali Lakes, 40% were within 15 cm of somethingsuch as a stick,rock or clumpof vegetation,even thoughthese wereusually scarce in the generalarea. Exceptfor 11% of the neststhat were in fiat (topographicrelief within a 1 m radiusless than 5 cm) areasaway from vegetationor other surface irregularities,the remaining nests were on substratewith enough topographicrelief or disruptivecoloration (sand- pebblesubstrate) to providesome concealment for the eggsand in many casesthe incubatingbird. At inland lakeswe usuallysaw broodsfeeding within a few metersof the. water. When disturbedthey often ran acrossdry open flats to avoid us. Chicksreadily hid in availablemarsh vegetation, particularly at the Alkali Lakes in Modoc County.

Disturbanceto Nesting Habitat Exceptat RosamondLake, habitatat eachbreeding site had apparently been alteredby human activitiesover the past 200 years.In the Central Valley agriculturaldevelopment has confined wetlands to suchan extentthat suitablebreeding habitat is largely depleted. The onlyhistorical nesting site of any sizewe were able to identify,Buena Vista Lake in Kern County, has disappeared.At severalbreeding sites in the Mohave Desertand the Great Basin, agriculturalor municipalwater demands have altered habitat. The moststriking examples, Owens Lake whichhas almost completely dried up, and Mono Lake whoselevels are rapidlydropping, held the largestconcen- trationsof birds.Because much habitat remains in theseareas and practically nothingis knownabout breeding numbers prior to the 1970s, we refrainfrom assessingthe effectof thesechanges on the plover.Man's intervention at the Salton Sea has produced breedinghabitat for a substantialnumber of plovers.Whether the additionalhabitat offsets the lossat other locationsre- mains unanswered. We saw nest predators,particularly Common Ravens, at almostall loca- tionssurveyed. One raven wasseen taking the eggsof a ploverand thoseof several American Avocets (Recuruirostraamericana) at Owens Lake. At Mono Lake CaliforniaGulls, ravensand Coyotes(Canis latrans) destroyed many plover nests (Page et al. 1979).

23 SNOWY PLOVER BREEDING STATUS

IV. SEASONAL VARIATION IN PLOVER NUMBERS

JOHN S. WARRINER and JANE C. WARRINER

To help interpretthe resultsof the statewidesurveys we studiedbreeding Snowy Ploversat Pajaro Dunes on MontereyBay, measuringthe degreeto which observerscould detect birds on censusesand definingthe species' migrationperiods. Pajaro Dunesis a beachfronthousing development at the Pajaro River mouth in extreme southwesternSanta Cruz County. Plovers breedon eitherside of the river mouth and on a smallunvegetated flat in salt marsh 1 km away. During I977 and 1978 we tried to find all nests, and at approximately7 day intervalscount all birdsin the area. Justprior to nesting in March 1978, 25 adults were individuallycolor banded by placingtwo stripsof differentlycolored plastic tape on each of two aluminumbands, one on each leg. Additionalbirds were later capturedon their nestsand similarly marked. From the time of markingonwards counts of marked and unmarked birds enabled us to use the Lincoln Index [P = (T x M)/N, where P = total number of ploversin area, T = total number of birdsseen on census,M =

I10-

I00--

90-

80-

70-

60-

50-

40-

.:50-

I0-

O- 20 29 6 12 19 26 2 I0 17 2430 7 14 21 305 1014 21 MARI APR I MAY i JUN I JUL

Figure la. Number of adult Snowy Ploverscounted (solidbar) and estimated(open bar) at Pajaro Dunes in the 1978 breedingseason. 24 SNOWY PLOVER BREEDING STATUS

number of marked birds known to be in the area and N - number of marked birdson census]to estimatethe total number of ploversin the area. Experiencedobservers conducted 19 censusesof ploversin the Pajaro studyarea betweenMarch and July 1978. The number of marked plovers sightedvaried between54% and 91% and averaged72% (s = 9.1%) of thoseassumed to be presentbecause they were sightedbefore and afterthe census(Figure la). Pajaro Dunes was a difficultarea to survey because ploversmoved between three separateareas. Due to the more difficultthan averagecensus conditions at Pajaro, Pageand Stenzel(pers. comm.) believe that on the coastalsurvey as a whole it was possibleto detectat least72% of the ploverspresent. The detectionrate for interiorsites may be lower since nestingareas, up to 3 km wide, were difficultfor two people to cover (Page pers comm.). It appearsthat most springmigrants and winteringbirds left Pajaro Dunes by early May. Of 19 markeddeparting birds most left between20 March and 26 April (Figure lb). Two remained until 2 and 8 May respectivelyand ex- hibitedsome nestingbehavior before leaving. Four of the 19 birdsreturned for briefperiods during summer before departing again. Markedbirds did not begin to return in numbersuntil early July (Figure lb). It appearsthat the most appropriatetime to conductthe statewidesurveys was May and June sincethis is the period that migrantsare leastlikely to be encountered. Some breedingbirds move betweenareas in May and June. For example, after 14 June 1978 nine ploversfrom failedPajaro nests were found 6 km to the south at MossLanding salt works. At leasttwo of the nine renestedthere. Two other birdsdispersed even farther, one turningup 27 km to the north- west at Wilder State Beach and one 75 km northeast at South San Francisco Bay. Midsummermovements of breedingbirds to and from a sitemay vary annually.In 1977 the breedingpopulation increased at Pajaro Dunesfrom early May to early June and then leveled off. In contrastin 1978 numbers were relativelyconstant in May but declinedin June. The aboveexamples il- lustratedthat repeated censusesof particularbreeding sites often produce variable numbers, hence any single censusmay not reflect the maximum capacityof the area to supportplovers that year.

20-

15-

,o_o- ill I ! . . I MAR I APR I MAY I JUN I JUL

Figurelb. Numberof marked,locally non-breeding Snowy Plovers on censusesat Pa- jaro Dunes in 1978.

25 SNOWY PLOVER BREEDING STATUS

DISCUSSION AND SUMMARY

GARY W. PAGE and LYNNE E. STENZEL BreedingSnowy Ploverswere distributedwidely over the state(Figure 2) but, unexpectedly,most were in the interiorrather than on the coast(Table 7). Apparentlyfew observershad exploredthe interiorso that the large number of birdsthere had escapednotice until this survey. On the coast, largerconcentrations of birdswere in the souththan in the north,suggesting the centerof the species'coastal distribution lies closer to the southernthan the northernboundary of the state;therefore, Baja Californiamay alsosup- port substantialnumbers of breedingbirds. Throughoutthe stateopenness of habitatseemed to be a key requirement for nesting.Of 116 nestsobserved on the coastand in the interior,46% were vegetation-freewithin a 10 m radiusand an additional23% lackedvegeta- tion within a 1 m radius. At only 12 nestsdid vegetationcover exceed 10% within10 m and at only 5 did it exceed10% coverwithin 1 m. Ploverswere absentfrom beachesheavily littered with driftwood. Accessto water is probably a breeding requirementalthough birds sometimesnested hundredsof metersaway when no obstacleprevented movementsof chicksbetween the nestand water. Thusplovers nest around shallow alkaline lakes where the waterlinemay retreat severalhundred metersfrom the nest during the month betweenthe laying and hatchingof eggs. We did not find ploversnesting on bluff-backedbeaches on the mainland as we did on San Miguel and San Nicolas islands. Island bluff-backed beacheswith plovershad generousareas of strandwhich were lightly vegetatedor were 50% or more coveredby driftwood,kelp, shellsor small rocks. In contrastthe upper strandon mainlandbluff-backed beaches was generallynarrow, barren and oftenwashed by the highesttides. The amount of availablehabitat at any site may vary seasonallyor from year to year. On the coastwinter stormsregularly erode beachesand fill lagoonswith water, thus reducingpotential breeding habitat. This reduction is followedby a slow increasein habitatduring spring and summerwhen beach width increasesand shrinkingwater levels in the lagoons expose suitablenesting flats. This processis relatedto the severityof winterstorms, which variesconsiderably from year to year. Similarly, intensityof winter rains, in the absence of human induced water diversions, determines whetherinterior breeding areas, such as shallow alkaline sinks, are dry, partly filled or flooded to surroundingvegetation. Thus the number of breeding Snowy Plovers may change annually or even mid-breedingseason, in responseto naturalalterations in habitatavailability. Humans have altered breedinghabitat, at least on the mainland coast. Some coastalareas have been developedto the extentthat they no longer supportplovers; at othersdisturbance probably reduces breeding numbers and lowersbreeding success. At ZmudowskiState Beachin MontereyCoun- ty the Warriners(unpubl. data) found hatchingsuccess to be much lower than on undisturbedsalt pan just 1 km away. At Zmudowskisome eggs were obviouslypicked up by peopleand otherswere probablystepped on. Others apparentlywere lostto high windswhen disturbedbirds were unableto in-

26 SNOWY PLOVER BREEDING STATUS cubateand preventtheir eggsfrom beingscattered and buriedby blowing sand. In some instanceshumans have enhanced habitat for the species throughthe constructionof saltevaporators in coastalbays or floodingof dry interiorareas. However, suchenhancement probably does not compensate for the degradationof other areas. Our conclusionsconcerning the plover'schange in statusover the past centuryare limitedby the paucityof historicaldata, particularlyfor the in- terior. Numbershave definitelydeclined on the coast; the specieswas not foundbreeding in 33 of the 53 locationswith breeding records prior to 1970.

•Im• BIG LAGOON GOOSEL' (I• !1UPPER ALKALlL '• ' ß MIDDLEALKALI L

••HUMBOLDT ....BAY AREAOiILOWERtONEY LALKALI L

_•,PTREYESB •.

\I s SA,.,,':RANCISCO BA• '-•

WILDERCRB •'--"•PAJAROR MOUTH ß '[11•EMA•'MARES

'k .

NUMBEROF ADULT i•SANTAMARIA R AREA ßHARPERL. • SNOWYPLOVERS i•FURISI•A-STA YNEZAR.OROSAMON D L '•

I7•6 -322 :ß II•SANNiCOL•AS• IS '•ik BALTON SEA ,-2 ß •, I•N BANDIE(SO CO •

Figure2. Distributionof breedingSnowy Plovers in Californiafrom 1977-80surveys. 27 SNOWY PLOVER BREEDING STATUS

Table 7. Number of adult Snowy Ploversfound during 1977-80 surveysin California.

Estimated Pairs Total Adults

Channel Islands 130 261 Mainland coast 498 954 San FranciscoBay 351 Interior 1843

TOTAL 3409

Of the 33 areas28 are not likelyto have regularbreeding populations again becausethe habitathas been destroyedor human useof the area is too great. The greatestlosses have occurredin southernCalifornia where breeding plovershave vanishedfrom parts of San Diego, Ventura and Santa Barbara counties,most of Orange County and all of Los AngelesCounty. In all these areas the plover's absencecan be correlatedwith industrialor residential developmentand/or heavy recreationaluse of former beachnesting areas. To the north, such human factorscome into play lessfrequently, although they may still have causeddeclines in placesaround Monterey Bay, at San Francisco,at Bodega Bay and the north spit of Humboldt Bay. Current emphasison coastaldevelopment for recreationby the State of Californiaprobably means a further lossof habitatfor the plover. If no ex- changeoccurs between interior and coastalbreeding populations, a subject currentlyunder investigation,then the statusof coastaland interiorpopula- tions mustbe consideredseparately. There may be a greatersurvival problem on the coastif there is no recruitmentfrom the lessdisturbed interior breeding areas. This surveylocated the importantCalifornia breeding sites and developed an index of the SnowyPlover's abundance against which future surveys can be compared. We encourageinterested persons to keep track of breeding numbersin areasnear them, especiallywhen habitatalterations are occur- ring, and to promote the protectionof importantbreeding sites.

ACKNOWLEDGMENTS This projectwas supportedby the membersof PRBO; contractsfrom the California Department of Fish and Game under Federal Aid in Wildlife RestorationProject W54R, NongameWildlife Investigations; and donations from the Union Oil Company Foundation of California. Rita Halbeisen, DouglasJudell, Lynda Orman, David Shuford, Chris Swarth and Ralph Widrig helped with the north coastsurvey; Mark Annis, Jonathan Atwood, Anthony Bledsoe, Gilberto Cabrera, Richard Erickson, Alice Fries, Jan Larsen, Peter Metropulos,Dennis Parker, Evelyn Peaslee, Michael Silber- nagle, Philip Unitt and the Warrinerswith the southcoast survey; and Bud Antonelis, Michael Hill and Robert Jackman with Channel Island surveys.

28 SNOWY PLOVER BREEDING STATUS

Hal Spear gave major assistancewith field work and the preparationof the manuscripton the Channel Islands;Alan Craig, Ronald Dow, Paul Kelly, Jan Larsen, A1 Vail and Nick Whelan assistedin obtainingaccess to the islands.We thank the many personsin the military,at saltponds, at oil fields, in the stateand nationalpark servicesand with The Nature Conservancy who provided us with accessto many restrictedlands along the coast.Jane Gull Mossand Robert Personiusof the South San FranciscoBay National WildlifeRefuge and JamesWalton of the LeslieSalt Companyalso helped arrange accessfor surveyson restrictedproperties. Volunteers who con- tributedto the studiesat PajaroDunes included Susan Corbus, Dorothy Lilly, Irene Manicci,Randy Morgan and Barry Sauppein 1977; SteveAllison, An- thony Bledsoe, Carolyn Frederiksen,Mark and Natalie Hopkins, David Ramer, Barbara and Chris Swarth in 1978; and Dorothy Hunt, Peter Metropulos,Dennis Parker, RobertRamer and Edna Vollmer in both years. Chris and Barbara Swarth, Ralph Widrig, David Bontrager, Lt. R.W. Cosgriff,Alice Fries, Evelyn Millar, Peter Robinson,Nancy and Hal Spear, A1Tucker and John and RickyWarriner generously extended hospitality to the personsconducting the coastalsurveys. Theunpublished field notes of persons listed in Appendix 3, JonathanAt- wood, Paul Collins,Lee Jones,Paul Roush,J.G. Tyler (suppliedby Robert Hansen),Ruth Wilsonand DavidWinkler greatly added to our knowledgeof the Snowy Plover in Californiaand Oregon. The followingcurators and curatorialassistants from institutionslisted in Appendix 3 provided nest or egg records: Dana Gardner and Lloyd Kiff (WFVZ), Bonnie Farmer (NMNH), Henry Pelzl (AMNH), G.D. Alcorn (UPS), LaurenceBinford and MatthewLeddy (CAS), Janet Hamher (SBMNH), EugeneCardiff (SBCM), David Willard (FMNH), C.G. Sibley (PMY), KennethParkes (CMNH), Ned Johnson (MVZ), Stanley Harris (HSU), Stanlee Miller (CU), David Niles (DMNH), MorrisWilliams (LSU) and RossJames (ROM). Alan Craig and Gordon Gould of the CaliforniaDepartment of Fish and Game helpedin- itiateand guidethis study through to itstermination point. Commentsby Jon Dunn, Jane Church,Gordon Gould, and JosephJehl, Jr. greatlyimproved early draftsof this manuscipt.Jane was particularlyhelpful with her con- tinous support and encouragementthroughout the entire project. To all thesepeople we extendour gratitudefor makingthe surveya rewardingand pleasantadventure. This is Contribution205 of Point Reyes Bird Observatory.

LITERATURE CITED

American Ornithologists'Union. 1957. Check-listof North American birds. 5th ed. Am. Ornithol. Union, Baltimore, MD. (0). Anon. 1971. National shorelinestudy Californiaregional inventory. U.S. Army Engineer Div., San Francisco.(0) Baldridge,A., T. Chandikand D. DeSante.1970. The nestingseason. Middle Pacific coast region. Aud. Field Notes 24:712-715. (1)

29 SNOWY PLOVER BREEDING STATUS

Barbour,M.G., T.M. DeJongand A.F. Johnson.1976. Synecologyof beachvegeta- tion alongthe Pacificcoast of the United Statesof America:a firstapproxima- tion. J. Biogeogr. 3:55-69. (2) Bent, A.C. 1929. Life historiesof North American shorebirds.Order Limicolae (Part 2). U.S. Natl. Mus. Bull. 146. (3) Booth, E.J. 1926. Observationsin the San FranciscoBay region. Condor 28:271. (4) Chandik, T. and A. Baldridge.1967. Nestingseason. Middle Pacificcoast region. Am. Birds 21:600-603. (5) Chandik, T. and A. Baldridge.1968. Nestingseason. Middle Pacificcoast region. Am. Birds 22:642-646. (6) Chandik, T. and A. Baldridge.1969. Nestingseason. Middle Pacificcoast region. Am. Birds 23:688-693. (7) Chase, T., Jr. and T. Chandik. 1966. Nestingseason. Middle Pacificcoast region. Am. Birds 20:595-598. (8) Chase, T., Jr. and R.O. Paxton. 1965. Nestingseason. Middle Pacificcoast region. Am. Birds 19:574-576. (9) Cogswell, H.L. 1947. Nestingseason. region. Aud. Field Notes 1:188-190. (10) Cutler, B.D. and E.A. Pugh. 1959. Nestingseason. Middle Pacificcoast region. Aud. Field Notes 13:450-454. (11) Dawson, W.L. 1923. The birdsof California. South Moulton Co., San Francisco,pp. 1314-1328. (12) DeBenedictis,P. and T. Chase,Jr. 1963. Nestingseason. Middle Pacific region. Aud. Field Notes 17:480-483. (13) DeSante, D. and R. LeValley. 1971. The nestingseason. Middle Pacific coast region: Am. Birds 25:899-904. (14) DeSante, D. and V. Reinsen. 1972. The nestingseason. Middle Pacificcoast region. Am. Birds 26:897-903. (15) Fisher,A.K. 1893. Reporton the ornithologyof the Death Valley expeditionof 1891, comprisingnotes on the birdsobserved in southernCalifornia, southern Nevada, and parts of Arizona and Utah. Pp. 7-158 in No. Am. Fauna 7. (16) Giles, L.W. and B.H. Crabb. 1958. Snowy Plovernesting on Lower KlamathRefuge, SiskiyouCounty, California.Condor 60:192. (17) Gill, R., Jr. 1972. South San FranciscoBay breedingbird survey, 1971. California Dept. Fish and Game Wildl. Manage. BranchAdmin. Rep. 72-6. (18) Grinnell, J. 1915. A distributionallist of the birds of California. Pac. Coast Avif. 11. (19) Grinnell, J., H.C. Bryant and T.I. Storer. 1918. The game birdsof California.Univ. California Mus. Vert. Zool., Berkeley. (20) Grinnell,J and M.W. Wythe. 1927. Directoryto the bird-lifeof the San FranciscoBay region. Pac. Coast Avif. 18. (21) Hill, H.M. 1941. Waterfowl breedingrecords from San Bernardino and Riverside counties, California. Condor 43:71-72. (22) Howell, A.B. 1917. Birds of the islandsoff the coast of southernCalifornia. Pac. Coast Avif. 12. (23) Jurek,R.M. 1974. Californiashorebird survey, 1969-1974. California Dept. Fishand Game Spec.Wildl. Invest.Proj. W-54-R FinalReport. 120 pp. (24) Lamb, C. and A.B. Howell. 1913. Notes from Buena Vista Lake and . Condor 15:115-120. (25) Linton,C.B. 1908. Notesfrom BuenaVista Lake, May 20 to June 16, 1907. Condor 10:196-198. (26)

3O SNOWY PLOVER BREEDING STATUS

McCaskie,G. 1968. Nestingseason. Southern Pacific coast region. Aud. Field Notes 22:647-650. (27) McCaskie, G. 1974. The nestingseason. Southern Pacific coast region. Am. Birds 28:948-951. (28) McCaskie, G. 1975. The nestingseason. Southern Pacificcoast region. Am. Birds 29:1029-1036. (29) McCaskie,R.G. and E.A. Pugh. 1964. Nestingseason. Southern Pacific coast region. Aud. Field Notes 18:534-536. (30) Meadows. D. 1934. Additional notesfrom Santa Catalina Island. Condor 36:40. (31) Page, G.W. and L.E. Stenzel, eds. 1979. The breedingstatus of the Snowy Ploverin California. CaliforniaDept. Fish and Game, Nongame Wildl. Invest. Rep. (32) Page, G.W., D.W. Winkler and C.W. Swarth. 1979. Breeding successof Snowy Plovers at Mono Lake, California. U.S. Fish and Wildl. Ref. and Wildl. Res. Rep. (33) Pickwell, G. 1930. The length and width of the home of the Snowy Plover. Wren-tit 2:1-2. (34) Pray. R.H. 1952. Nesting season. Middle Pacific coast region. Aud. Field Notes 6:297-299. (35) Pyle, R.L. and A. Small. 1951. Nestingseason. Southern Pacific coast region. Aud. Field Notes 5:306-309. (36) Quigley, R., Jr. 1955. Snowy Plover: a photograph. Condor 57:239. (37). Sibley,C.G. 1952. The birdsof the southSan FranciscoBay region. Publ. by author, mimeo. 44 + vii pp. (38) Slobodchikoff,C.N. and J.T. Doyen. 1977. Effectsof Ammophila arenaria on sand dune arthropod communities. Ecol. 58:1171-1175. (39) Stager, K.E. 1949. Nesting season.Southern Pacificcoast region. Aud. Field Notes 3:252. (40) Stallcup, R. and J. Winter. 1975. The nestingseason. Middle Pacificcoast region. Am. Birds 29:1025-1029. (41) Tyler, J.G. 1916. Some birdsof the Fresnodistrict, California. Condor 18:194-198. (42) Unglish,W.E. 1938. Snowy Plover nestingin Merced County, California. Condor 40:40-41. (43) Walker, L.W. 1935. On a southern California beach. Bird-Lore 37:119-121. (44) Wilcox, L.R. 1959. A twenty year banding study of the Piping Plover. Auk 76:129-152. (45) Willett, G. 1912. Birdsof the Pacificslope of southernCalifornia. Pac. CoastAvif. 7. (46) Willett, G. 1933. A revised list of the birds of southwestern California. Pac. Coast Avif. 21. (47) Winkler, D.W., C.P. Weigen, F.B. Engstromand S.E. Burch. 1977. Ornithology. Pp. 88-113 in An ecologicalstudy of Mono Lake, California. Inst. Ecol. Publ. 12, Univ. California, Davis. (48) Winter, J. and D. Erickson.1976. The nestingseason. Middle Pacificcoast region. Am. Birds 30:996-1001. (49) Yocom, C.F. and S.W. Harris. 1975. Birds of northwestern California. Humboldt State Univ., Arcata, CA. 68 pp. (50)

31 SNOWY PLOVER BREEDING STATUS

APPENDIX 1. Surveyresults and historicalrecords of SnowyPlovers breeding in mainland California. Locationsare listedfrom southto north, first along the coast, then at San Francisco Bay,and then inland. Under Survey Status the estimatednumbers of adults(A) or pairs(P) is givenunless habitat was not presentwhen visited due to erosion,flooding or draining(E), the habitathad been destroyed or madeunsuitable by humanactivity or development(D), apparent- ly suitablehabitat was present but ploverswere not seen(H), or the areamentioned was not surveyed(W). UnderRecords, the mostconvincing evidence of breedingis given,with the numberof: adultsreported during May or June(A), pairsreported in Mayor June(P), females reportednesting (F), broods(B), chicks(C), or nests(N). An N withouta numberis given when a sourcemakes a generalreference to SnowyPlovers breeding. Under Source, initials refer to in- dividualsor institutionslisted in Appendix3, numbersto referencesin the literaturecited, and in- itialswith numbersto informationfrom museumegg set or specimenrecords. Max. untferEgg Setsin MuseumEgg Collections is the maximumnumber of eggsets collected during one 5 day period. Survey Egg Setsin Status Records Museum Collections

MAINLAND COAST Numbers Year Source Total Max. Years

San Diego County Tijuana R Mouth P 19 N1 1973 KB N1 1977 PJ Silver Strand Beach P 3 N1, B1 1930s 44 18 3 1918-1940 SilverStrand Bay Shore P 3 N1 1977-78 PJ,DP San Diego Bay P 16 A 1973 KB Salt Works N2 1975 BM N20' 1977 PJ Sweetwater R Mouth P 9 A 1973 KB 3 1 1931-1938 A 1977 PJ A20,B5 1978 DP North Is NAS H N2 1979 EC,DP LindberghField W N1 1979 EC,DP Ocean Beach E,D 5 3 1904-1917 San Diego: site unk. 4 1 1894-1938 MissionBay Beach D 23 4 1915-1930 MissionBay Fill H N1 1972 SL,LOCU N1 1977 PJ Pacific Beach D 4 2 1904-1916 PenasquitosLagoon H N2 1977 PJ A4 1978 DP Del Mar Beach E,D 19 8 1922-1954 San Elijo Lagoon P 12 N1 1976 PJ BatiquitosLagoon P 3 A18,N1 1970 He 3 1 1932-1936 A75,N5 1971 He A39,N,B5 1978 DP Agua Hedionda P 27 A9 1973 KB Lagoon A60 1975 BM N2 1977 PJ Buena Vista Lagoon D B1 ' ' 1951 36 None 1977 PJ

32 SNOWY PLOVER BREEDING STATUS

APPENDIX 1 (Cont.)

Survey Egg Sets in Status Records Museum Collections

Numbers Year Source Total Max. Years

Oceanside to Santa P 37 N8 1971 DS,LOCU 12 1917-1928 MargaritaR Mouth N7. 1972 DS, LOCU N1 1973 DS, LOCU N10 1974 AF,LOCU A20,C17 1975 BM N,C 1977 PJ French Creek Mouth P 2 Cl 1979 DP

Orange County Balboa Beach D 3 1907-1917 Newport Beach D 39 1893-1928 D N1 1955 37 21 1917-1940 Bolsa Chica Beach D None 1947 10 12 1905-1907 Bolsa Chica Salt Flats P 10 2 1960-1961 Sunset Beach D 1 1916 Sunset Beach Bay Fill H N1 1970 BM N2 1971 BM C1 1973 KB Anaheim Landing D 1907

Los Angeles County Redondo Beach W 24 1894-1904 Manhattan Beach W N1 1947 10 Playa del Ray D N4 1914 3 1 1914 P. del R. Salt Flats H 1 1923 Ballona Beach D P50 1903 NMNH 46 1894-1904 31481 Santa Monica/Malibu D,W N6 1938 WFVZ 1895-1947 3497 N1 1949 40 NiggerSlough W 2 1895 Los Angeles:site unk. W 14 1883-1905

Ventura County Mugu Lagoon Spits P41 N,C 1973 KB N1 1976 SW P15,N1 1977 BM Ormond Beach P14 C1 1975 SW 22 1896-1937 McGrath Lake Beach P3 Santa Clara R Mouth P13 A30,N6 1975 SW A25 1976 SW Ventura Beach D,H 1915-1948

Santa Barbara County Carpinteria-Sandyland E,D N1 1960 FM 25 1909-1946 Santa Barbara Beach E,D 15 1891-1933

33 SNOWY PLOVER BREEDING STATUS

APPENDIX 1 (Cont.)

Survey Egg Setsin Status Records Museum Collections

Numbers Year Source Total Max. Years

Goleta Beach E,D P24 1927 WFVZ 16 3 1927-1948 31500 A 1970s SW GoletaSlough Flats H 2 1 1934-1936 Santa Ynez R Mouth P5 A 1970s SW Purisima Point Beach P55 South Nipomo Dunes P4 Santa Maria R Mouth P18

.SanLuis Obispo County No. Nipomo Dunes P2 Pismo Beach D N2 1965 LOCU Morro Bay Area P40 N1 1974 EJ 18 4 1926-1934 Spit and Beachto N C 1977 EJ

Monterey County Point Sur Beach P2 Pacific Grove E,D 2 1 1916 Monterey-Seaside E,D 8 3 1875-1899 Marina Beach P12 SalinasR Spit P16 B2 1967 5 24 4 1894-1938 A 1968 6 A5-16,C0 1972 DPi,15 A50+ 1976 SW MossLanding Beach: P6 N5 1930 34 38 8 1895-1948 (SalinasR-Pajaro R) C1-4,N1 1948-53 VA,35 A20,C1 1963 13 A5,N0,C0 1965 9 A10,N0,C0 1966 8 N 1971 14 MossLanding P24 B1 1967 5 Salt Works N1,B2 1954 VA

Santa Cruz County PajaroR Mouth & P17 N7,C14 1972 15 1S 4 1893-1940 Palm Beach N7 1973 JW:LOCU N10 1975 41 Santa Cruz Beach D 5 2 1877-1878 Wood's Lagoon D 1 1 1876 Moore Cr Mouth D 1 1 1887 Wilder Cr Mouth P8 F2 1922 CAS70154, 70155 N 1976 49 Four-Mile Beach 1 1 1929

34 SNOWY PLOVER BREEDING STATUS

APPENDIX 1 (Cont.)

Survey Egg Setsin Status Records Museum Collections

Numbers Year Source Total Max. Years

Laguna Cr Mouth H B1 1979 EV Scott Cr Mouth D 4 2 1878-1946 Waddell Cr Mouth H B2 1979 PM Meader's Beach W 1 1 1878

Son Mateo County Aria Nuevo Beach P5 P 1968 6 C1 1969 7 Franklin Point E 1 1 1905 Pescadero P2 N pre-1927 21 N 1975 PM

Marin County BolinasLagoon Spit P1 N1-2 1970s GP,LS LimantourSpit P4 N1 1967 PL:LOCU N 1970s GP,LS DrakesBeach Spit P1 PointReyes Beach P15 N1 1926 4

Sonoma County BodegaHarbor Spit H C 1960s GB Salmon Creek Beach H N 1978 DFS

Mendocino County MacKerricher Beach P9

Humboldt County So. Humboldt Bay Spit P4 Elk R Spit P1 1 1 1920 No. HumboldtBay Spit P6 A 1910s 12 22 2 1899-1948 LanphereDunes P2 Mad R Spit P10 C2 1976 PK 2 1 1931-1935 Clam Beach P1 Carson'sLanding Penin. H 1 1 1935 Big LagoonBar P8

Del Norte County Lake Talawa Beach P3 P1 1974 50 Smith R Spit P4

SAN FRANCISCO BAY

Santa Clara County So. San FranciscoBay A14 N15 1971 18 Alviso C 1950 38 N3 1959 11

35 SNOWY PLOVER BREEDING STATUS

APPENDIX 1 (Cont.) Survey Egg Sets in Status Records Museum Collections

Numbers Year Source Total Max. Years Son Mateo County So. San FranciscoBay A19 Belmont A2 1972 24 N 1975-76 41,49 Bair Island A2 1977 TM Redwood City 1919

Alameda County So. San FranciscoBay A318 P many 1910s 20 DumbartonBridge N 1971 14 N1 1975 JA:LOCU Hayward N 1965 9 West of CoyoteHills N1 1972 HP Bay Farm Island A1,C1 1974 ER A8 1977 TM AS 1979 LF Alameda So. Shore A2-8 1971-77 ER A1 1978 ER

Napa County Little Is. Evaporator N3 1975 RG

INTERIOR OF STATE

Imperial County Salton Sea A226 N 1933 47 1 1929-1950 N 1968 27 A0-10 1971-74 24

RiversideCounty Salton Sea A10 Lake Elsinore E N1 1939 22 2 1 1948 C1 1940 22 C3 1974 28

Son Bernardino Count• Harper Lake A61 A68,N1,B3 1977 PH Seaties Lake A16

Kern County Rosamond Lake A6 Koehn Lake A26 Goose Lake A2 Buena Vista Lake D N1 1907 26 P 1912 25 Kings County Corcoran Reservoir A1 Tulare Lake D A 1912 12

36 SNOWY PLOVER BREEDING STATUS

APPENDIX 1 (Cont.)

Survey Egg Setsin Status Records Museum Collections

Numbers Year Source Total Max. Years

Madera County East of Firebaugh W P1 1915 42

Merced County Los Banos H A 1912 12 4 1 1937-1939 A 1914 12 N5-6 1937 43

Yolo County Davis SewagePonds W C 1963 13 Woodland Sewage W B1 1970 1 Ponds lnyo County Tecopa Marsh A7 Al-12 1974-77 JT Owens Lake A499 A"many" 1893 16 A130,C 1975 29 Salt Lake A1 A2 1977 PH Tinemaha Reservoir A2 Deep SpringsLake A13 N2 1964 30 A30 1971 RL

Mono County Mono Lake A384 N3,B6 1976 48 A90,N8 1977 GP,SP

Butte County Near Reigo W 1 1 1913

Lassen County Honey Lake A208 P2 1977 DG EagleLake H A3 1948 fide DA

Modoc County Lower Alkali Lake A92 Middle Alkali Lake A36 Upper Alkali Lake A230 Goose Lake A33 A 1912 12

$iskiyou County Lower KlamathRefuge H N 1957 17 A 1971-73 24

' Observerfound total of 20 nestsduring nesting season; some may have been renests.

"This record is questionableas observerfound a four-chickbrood, which is a very unusualbrood-size for Snowy Plovers.

37 SNOWY PLOVER BREEDING STATUS

APPENDIX 2. Sites not listed in Appendix 1 where apparently suitablehabitat was surveyedfor breeding Snowy Plovers are listed below by county.

ALAMEDA: Alameda Naval Air Station. DEL NORTE: Klamath River mouth, Crescent Beach, Pebble Beach, Pelican Beach. HUMBOLDT: Mattole River mouth, McNutt Beach, Eel River spits,Little River spit, Agate Beach, Dry Lagoon bar, Stone Lagoon bar, FreshwaterLagoon bar, Gold BluffsBeach, CarruthersBeach. KERN: Rogers Lake, Pazuza Land and Water Company, Kern . KINGS: Hanford Sewage Ponds. LASSEN: Eagle Lake, Horse Lake. MADERA: Madera Lake. MARIN: Cronkhite Beach, Dillon Beach. MENDOCINO: Manchester Beach, Navarro River mouth. MERCED: Volta Wildlife Area, Santa Fe Grade (road from Gustineto Los Banos), Merced National Wildlife Refuge. MODOC: Clear Lake. MONTEREY: Little Sur River mouth, Carmel River mouth, Carmel Beach, Moss Beach, Spanish Beach, south shore. NAPA: North San Francisco Bay marshesand saltevaporators. ORANGE: San Juan Creek mouth (), Aliso Beach, Corona del Mar State Beach. RIVERSIDE: San Jacinto Reser- voir, Ford Lake, Palen Lake. SAN BERNARDINO: Dale Lake, Danby Lake, Cadiz Lake, Bristol Lake, West Cronese Lake, East Cronese Lake, Soda Lake, Silver Lake. SAN DIEGO: Naval Training Center, San Diego Flood Control Channel, San DieguitoCreek mouth, CockleburrCanyon mouth, San Onofre Creek mouth, San Mateo Creek mouth. SAN LUIS OBISPO: CayucosCreek mouth, Villa Creek mouth, Santa Rosa Creek mouth, San Simeon Creek mouth, Pico Creek mouth, San Simeon Beach, Soda Lake. SAN MATEO: Half Moon Bay, Linda Mar Beach (San Pedro Creek mouth). SANTA BARBARA: Devereaux Beach, Devereaux Slough, Bell to Tecolote Creek mouths, El Capitan Beach, Refugio beach, Gaviota Beach, Canada de Santa Anita mouth, Arroyo El Bulito mouth, Jalama Beach. SANTA CRUZ: , Moran Lake, Cocoran Lagoon, Schwans Lagoon, County Dump Gulch, Major's Creek mouth, San Vicente Creek mouth, Davenport Landing Beach. SOLANO: North San Francisco Bay marshes and salt evaporators. SONOMA: RussianRiver mouth, Gualala River mouth. TULARE: Pixley National WildlifeRefuge. VENTURA: CalleguasCreek (creekbars from Highway 101 to Lewis andLas Posas Roads), Silver Strand, Hollywood Beach, Santa Clara River bars (Har- bor Blvd. north 8.4 km).

APPENDIX 3. Unpublished sources of Snowy Plover nest or egg records and breedingpopulation estimates for variouslocations, with abbreviationsused in Appen- dix 1 or the text.

Daniel Airola DA, J. Anderson •IA, Vivian Anderson VA, Kristen Bender KB, Gordon BolanderGB, ElizabethCopper EC, Leora Feeney LF, Alice FriesAF, David Gaines DG, Robert Gill RG, John and Dorothy Helmer He, Philip Henderson PH, Eric JohnsonE•J, Paul JorgensenP•J, Paul Kelly PK, Philip Lenna PL, Ronald LeValley RL, S. ListonSL, Flora MacliseFM, TimothyManoils TM, BarbaraMassey BM, Peter MetropulosPM, Gary Page, GP, Dennis Parker DP, Susan PeasleeSP, Henry Pelzl HP, Donald Pine DPi, ElsieRoeruer ER, David F. ShufordDFS, Lynne StenzelLS, Dean SwickardDS, •lan Tarhie •JT, •lohn G. Tyler (unpub. field notes)•JGT, Edna Volliner EV, Jane (Ricky) Warriner •JW, Sanford Wilbur SW.

AmericanMuseum of Natural HistoryAMNH, CaliforniaAcademy of SciencesCAS, Carnegie Museum of Natural History CMNH, Clemson University CU, Delaware 38 SNOWY PLOVER BREEDING STATUS

Museumof NaturalHistory DMNH, FieldMuseum of NaturalHistory FMNH, Hum- boldtState University HSU, Laboratoryof Ornithology,Cornell University LOCU, Museumof Zoology, Louisiana State University LSU, Museum of VertebrateZoology, Universityof CaliforniaMVZ, NationalMuseum of NaturalHistory NMNH, Peabody Museum,Yale UniversityPMY, Museumof NaturalHistory, University of Puget SoundUPS, RoyalOntario Museum ROM, SanBernardino County Museum SBCM, Santa BarbaraMuseum of NaturalHistory SBMNH, and WesternFoundation of VertebrateZoology WFVZ.

Accepted24 January 1981

Publicationof this paper was made possibleby substantialcontributions by Point ReyesBird Observatoryand the CaliforniaDepartment of Fish and Game. -- Editor

Snowy Plover, Mono Lake. California, June 1980. Photo by lan C. Tait

39 t .