The Occurrence of Seabirds in the Coastal Region of California

WESTERN BIRDS

Volume 7, Number 2, 1976

THE OCCURRENCE OF SEABIRDS IN THE COASTAL REGION OF CALIFORNIA

DAVID G. AINLEY, Point Reyes Bird Observatory,P.O. Box 321, Bolinas,Cali- fornia 94924

Abundanceand speciescomposition of marine birds are specificto different oceanographicregions; these in turn are definedby character- istic physicaland biologicalconditions. This has been discussedmost graphicallyby Murphy (1936, 1967), Kuroda (1955), Sanger(1970, 1972), and Shuntoy(1972). Ideally, biologistsshould be familiar with the physicaland biologicalenvironmental factors affecting the occurrence of marine birds, since the diversity of environmentalconditions that often occurover equal areas on land is not present. Yet our under- standingof how oceanfactors affect seabirdabundance and distribution is incompletebecause of the relative inconvenienceand expenseof studyingpelagic life, and the fact that marinebiologists as a general rule ignorebirds (Ashmole1971, Sanger1972). The distributionof marine birds in the North Atlantic (see Wynne-Edwards1951, Murphy 1967) and Central Pacific oceans(see King 1970, 1974) is relatively well known, but little work has been done elsewhereexcept in restricted areas(e.g. Sanger1970). One of the oceanographicallybest known areasin the world is the CaliforniaCurrent region off Californiaand Baja California. Informa- tion has been amassedthrough efforts of componentagencies in the California CooperativeOceanic Fisheries Investigations (see Cal-COFI Reportsand Atlases).However, knowledge of birdsin this areahas nev- er been intensivelyanalyzed except locally, e.g. Monterey Bay (Loomis 1895-96, Beck 1910, Baldridgeunpubl.), or for a few selectedspecies, e.g. Black-lootedAlbatross (Miller 1940, McHugh 1950, Thompson 1951, Sanger1974a). WesternBirds 7:33-68, 1976 33 SEABIRD OCCURRENCE

In California,boats have frequently been charteredto observemarine birds in the nearshoreregion of the CaliforniaCurrent 15 to 80 km offshore. This paper discussesseabird abundance and distributionin this coastalarea basedon analysisof observationspublished from 1955 to 1973 in American Birds (formerly Audubon Field Notes). Where possible, an attempt is made to correlateseabird occurrence to oceanographic conditions. Bird observationswere lessfrequent prior to 1960 than subsequently,but extremelyinteresting oceanographic conditions occurredfrom 1955 to 1960. I thereforeincluded that early periodin the analysis.

ß..:-ß ,,,,•.O_REGON

".. "•.•,""-' • SCALE:30KM '•,•A•.,.•/"• ",•'FIODEGA BAY • "• •d o • F ARALL'QN':,, •hSAN FRANCISCO •_ ":. '•GEO N POINT / • ..'.. -._,'

• {':.•g.... • ::"•/•.• :.." ',.,•MORR ",,•:•w•0

.. • ' , :• ',••,• •,•' .: :.. '. _--•• ',•::'.s•, ß.: '. •"•--•'•7 ',,[

'"'.. - C• I• •'., '

Figure 1. California coastalgeographic areas and placesmentioned in the text. 34 SEABIRD OCCURRENCE

Table 1. A summary of oceanographicand cruisecharacteristics for each of the study areas.

MEAN REGION OCEAN DISTANCE WATER TEMP. øC SALINITY AREA COVERED AREA TO SHORE MEAN(X) RANGE RANGE %o

1 Cape West of 30-60 km X=10.7 30.7-34.5 Mendocino Cape 8.3-14.9 2 Bodegato Farallon Is. 30-40 km X--12.1 28.9-34.5 PigeonPt. and shoals 9.2-16.1 3 Monterey Monterey 15-25 km X--13.1 31.6-34.5 Bay Canyon and 10. 4-16.4 Pt. Pinos 4 Morro Bay N. Channel 30-60 km Avila* 30.5-34.5 to Los Islands 10.5-18.0 Angeles S. Barbara* 12.0-20.1 Los Angeles San Clemente 15-80 km X=16.7 33.0-34.0 to San Is., Los 12.2-22.1 Diego Coronados Is.

*Mean temperatures not available; observationstoo infrequent.

METHODS AND STUDY AREA

Censusareas. The coastwas divided into five census areas according to the distributionof portsfrom whichboat trips departedand the oceanareas covered (Figure 1). Theseareas, with generalocean conditions,are reviewedin Table1. Trip coverageof the five areasduring the 19-yearstudy periodis summarizedin Table 2. Analysisof bird data. Bird recordswere taken from the regional reportspublished four times eachyear from 1955 to 1973 in American Birdsand its predecessorAudubon Field Notes. A regionaleditor sum- marizessightings for the seasonfrom informationon numbers,species, dateand route,sent in by bird observers.Almost all boat trips are "led" by at leastone observer having extensive knowledge and experi- encein the identificationof pelagicspecies. The two AmericanBirds regionscovered here are the SouthernPacific Coast Region (San Diego north to PointConception) and the MiddlePacific Coast Region (Point Conceptionto the Oregon-Californialine). Certaincharacteristics of the data haveaffected the analysis.First, speciesthat breedin Californiaand are commonlyseen were rarely in- cludedin the reportsso that, with a few exceptions(e.g., the storm- petrelsand Xantus'Murrelets), sufficient data for analysiswere avail- ableonly for speciesbreeding outside California. Also, most species of Larusgulls were excluded from reports.I did not analyzereports of jaegersor phalaropesbecause of the preponderanceof observations 35 SEABIRD OCCURRENCE

Table 2. A summary of coveragefor eachyear and for areasnorth (N) and south (S) of Point Conception. The number of trips (dates) in each of the regionsis shown. Shore observationswere included if gatheredas in a "sea watch" but miscellaneousreports, e.g., "two Marbled Murrelets were seen from shore at PigeonPoint" were not included.

YEAR AREA MONTH J F M A M J J A S O N D TOTAL

1955 N 2 2 i i 4 3 2 2 17 S 1 2 2 1 1 7 1956 N 1 2 1 2 3 4 4 3 4 24 S 1 1 2 3 7 1957 N 1 2 2 1 2 1 i 4 2 15 S 1 3 2 2 8 1958 N 2 1 3 2 3 1 1 13 S 2 1 1 1 2 4 4 2 17 1959 N 1 1 1 2 i 1 4 3 2 1 17 s 1 2 2 1 3 1 10 1960 N 2 i i 3 3 10 S i i 1 3 3 2 11 1961 N 1 I 2 S i 2 2 i 2 i i i 11 1962 N i i 2 i i I 2 9 S i i i I 4 1963 N I I i 2 1 2 2 10 S i i I i 4 1964 N 1 1 I 1 1 1 I 2 I 12 S i I 2 1 i 1 7 1965 N I i i I 2 I I 8 S 1 1 1 1 1 5 1966 N 2 1 1 2 2 3 1 1 13 S 1 1 1 1 4 1967 N 1 1 1 2 1 1 1 2 10 S 1 1 1 1 1 1 6 1968 N 1 2 1 3 1 2 2 3 2 1 1 19 S 1 i 2 1 1 i i 1 9 1969 N i i i 2 1 2 3 i i 5 2 i 21 S i 1 i 1 4 1970 N i i I 2 i 2 3 i 1 5 2 i 21 S i i i I i 2 i 8 1971 N I i i 2 4 i 3 3 2 4 2 I 25 S i i I I i i 1 1 8 1972 N 1 i 4 i 3 3 2 4 I 2 22 S i 2 i i 3 i 9 1973 N 2 2 i 2 1 4 3 2 i 18 S 2 i 2 i i I 8

TOTAL N 15 12 12 26 25 13 26 27 3O 48 32 19 S 12 4 8 9 16 10 7 16 28 10 19 8

made from shore, and I did not analyze Brown Pelican(Pelecanus oc- cidentalis)reports since analysisof their occurrencepatterns are pre- sented elsewhere (Anderson and Anderson 1976). Second, the detail of quantitativeremarks in the Audubonreports usually decreased as the abundanceof the speciesincreased. For example,every Flesh- footed Shearwaterwas countedand reported,since usually no more 36 SEABIRD OCCURRENCE

Table 3. A summaryof data usefulin assessingthe relativeabundance of,species in each study area and to a lesserextent the relative abundanceof one speciescompared to another. For each speciesin each study area are given the mean number of birds reported per year in years when reported followed by the number of years reported in parentheses;below those two numbersis the range of numbersreported all yearsconsidered. The rarest speciesare not included.

SPECIES STUDY AREAS 1 2 3 4 5 Black-footed Albatross 109 (6) .13 (15) 40 (17) 8 (4) 17 (14) 2-200 2-100 1-225 1-20 1-48 Laysan Albatross 2 (1) 2 (1) 1 (3) 1 (1) o Northern Fulmar 46 (4) 101 (9) 400 (15) 89 (7) 70 (9) 1-150 1-500 1-2000 1-200 1-200 Flesh-footed Shearwater 2 (3) 2 (4) 2 (8) 1 (1) 2 (7) 1-3 1-3 1-4 - 1-9 Pink-footed Shearwater 72 (3) 28 (14) 55O (10) 155 (4) 448 (13) 1-200 1-102 19-2000 1-950 2-2200 Sooty Shearwater - 3x10S(12) 3x10S(11) 2x10•(8) 9x104(11) 150-106 4000.106 4000-10 • 11-10 • Short-tailed Shearwater 2 (4) 2 (7) - 3 (5) 1-2 1-8 1-4 Manx Shearwater 62 (5) 62 (10) 105 (8) 605 (13) 1-300 1-500 1-300 9-5000 Buller's Shearwater 105 (6) 81 (7) 77 (17) 59 (3) 4 (4) 1-400 5-401 1-500 1-175 1-9 Fork-tailed Storm-Petrel 1 (3) 2 (5) 27 (15) 10 (3) 1 (1) 1-6 1-250 1-27 Leach's Storm-Petrel 1 (1) 15 (1) 2 (8) 16 (4) 165 (11) 1-8 2-50 1-465 Ashy Storm-Petrel 13 (3) 13 (5) 1820 (16) 23 (4) 19(11) 1-35 1-39 1-7000 10-50 1-70 Black Storm-Petrel 1 (1) 0 375 (17) 18 (4) 211 (14) 1-5000 2-50 8-1000 Least Storm-Petrel 1 (1) 0 3 (3) 500 (1) 420 (9) 2-3 1-3600 Wilson's Storm-Petrel 0 0 1 (6) 1 (1) 1 (1) 1-2 Blue-footed Booby 0 0 4 (1) 7 (1) 4 (3) 1-11 Magnificent Frigatebird 0 1 (3) 3 (2) 3 (8) 6 (13) 1-5 1-14 1-32 Red-billed Tropicbird 0 0 1 (1) 1 (3) 4 (8) 1-2 1-12 Skua 1 (2) 2 (7) 4 (13) 2 (3) 2 (3) 1-8 1-16 1-2 1-4 Sabine's Gull - 46 (7) 47 (8) 23 (7) 63 (13) 1-98 15-100 5-100 2-200

37 SEABIRD OCCURRENCE

Table 3 (cont.) SPECIES STUDY AREAS 1 2 3 4 5 Black-leggedKittiwake 1 (1) 56 (6) 1311 (8) 131 (4) 91 (9) 5-200 2-5000 10-500 1-500 Horned Puffin 1 (1) 1 (3) 1 (4) 2 (2) 1 (1) Marbled Murrelet 21 (2) 11 (5) 9 (8) 12 (4) 4 (3) 3-39 1-32 2-11 1-45 1-8 Ancient Murrelet 10 (3) 22 (8) 31 (8) 11 (7) 14 (4) 5-20 1-86 1-80 1-33 3-50 Xantus' Murrelet 1 (1) 2 (3) 7 (10) 21 (7) 53 (10) 1-6 1-19 7-57 2-354 Craveri's Murrelet 0 0 2 (2) 2 (2) 2 (5)

NOTE: The lack of information on the occurrenceof a speciesin a region is treated in two ways. If it is likely that the specieswas just not reported (e.g.Sooty Shearwaterin area1) thena dashis inserted;if it is probablethat the speciesdid not occurin a region (e.g. Blue-footedBooby in area 2) then a zero is inserted.

than a few were seen each season;but Sooty Shearwatersoften were reported with qualitative descriptions,such as abundant, scarce,etc., the meaningsof which differ with region, observer,editor, and reader. Thus an analysisis restricted for abundant species. Third, on some trips few numbersor only common local specieswere seen,and thus reports were not published. Finally, bird trips in the Cape Mendocino area have been few, so analysisfor this regionis evenmore preliminary. In spite of theseshortcomings, the Audubonreports constitute an important bank of information,as shouldbecome evident in the following pages. Relativeabundance of eachspecies among the five areasis compared in Table 3. Only the most generalcomparisons are possible,but I thought that some sort of analysisof relative abundanceshould be at- tempted. The meannumber reported in yearswhen reported, the range in numbersfor all yearsconsidered, and the numberof yearsreported duringthe 19-yearperiod are all givenfor eachspecies within eachstudy area. Absolute,precise statements on bird density cannot be madeon the basisof thesedata, and only grosstrends in relativeabundance of speciesamong censusareas can be assessed;for example,fulmars are much more abundant in areas 3-5 than in 1-2, and not fulmars are four times more abundantin area 3 than in area 2. To compareabun- danceof onespecies relative to another,one has to be evenmore care- ful. The meannumber, the rangein valuesand the numberof yearsin which eachspecies was reported all haveto be considered.Only where the mean numbersfor one speciesdiffer by one to two or more orders of magnitude from the mean of another would I considerthat one speciesmight be more abundant; even then the difference will be tem- 38 SEABIRD OCCURRENCE

Table 4. A summary of hydrographicdata coverage.

TEMPERA- SALIN- AREA LOCATION YEAR7S TURE ITY AGENCY

1 Blunt's Reef, 1956-1972 X X U.S. Coast Guard Mendocino Co. 2 Farallon Is., 1956-1971 X X U.S. Coast Guard San Francisco Co. 1971-1973 X X Pt. Reyes Bird Obs. 3 Pacific Grove, 1956-1972 X X Hopkins Marine Sta. Monterey Co. 4 Avila, 1956-1972 X X U.S. Coast & San Luis Obispo Co. Geodetic Survey Santa Barbara, 1956-1972 X S.B. Harbor Dept. Santa Barbara Co. 5 La Jolla, 1956-1972 X X ScrippsInstitution San Diego Co. of Oceanography 1-5 Cape Mendocino 1963-1973 X U.S. Coast Guard to La Jolla Airborne Radiation Thermometer Program

pered by consideringthe other two types of valuesin the table. Take for example Manx and Buller's shearwatersin area 3. An averageof 62 Manx have been reported for the 10 years when reported, and an averageof 77 Buller's have been reported for the 17 years they were reported. The samerange in valueshave been reported for both species. They thus seemto occur in about equal abundancein area 3, but the Buller's Shearwater seems to occur more often. As one moves south into areas 4 and 5, Manx Shearwatersobviously become much more abundantthan Buller'sand are seenmuch more frequently. In the case of Sooty Shearwaters,estimates for bird numbersbased on qualitative descriptions were treated as follows: "millions" and "abundant"=1 million birds; "common" and "thousands"--500 thousand; "hundreds"= one to 100 thousand; "scarce"=less than one thousand. These defini- tions were basedon comparisonwith my own censusesmade twice per month for four years in the Farallon Island area. Seasonalabundance was calculated in two ways; one summarizesall data from all five areas (Figure 2), and the other comparesseasonal abundancebetween areas north and south of Pt. Conception,a natural oceanographicboundary area (Hubbs 1963; Figure 3). In the first, the number of birds reported in the 19 years was totalled by speciesfor eachmonth. Percentagesof the totals were then figured for eachmonth, and the results were compared to the nesting cycle of each species based on publishedinformation. In the other analysis,monthly per- centageswere figured for areas 1, 2 and 3 combined and were com- paredwith combinedpercentages for areas4 and 5. Yearly abundanceof each species(Figure 4) wascalculated with the 39 SEABIRD OCCURRENCE formula: (X x Y)/Z, where X is the total number of birds per species reported that year, Y is the numberof areasreporting that species,and Z is the numberof dates(trips) on which the specieswas reported. The resultswere then graphedfor each species. The year havinghighest "abundance"was give n a scoreof 10 with valuesfor otheryears being scoredproportional to that one. Thusscores are comparableonly within species,although one can comparespecies to seewhether year-to-year trends are similar or different. Analysisof oceanographicdata. Data Reportsof the ScrippsInsti- tution of Oceanography,published annually for the years1956 through

75' Black-footedAIbatross 25 ÷ rwate•Man•xShae 75' NorthernFulmar

z w 75' Flesh-footedShearwater Fork-tailed Storm Petrel n• n• • 25

75' Pink-footedShearwater Leach's Storm-Petrel

I-- ' Z

75' SootyShearwater Ashy Storm-Petrel

25'

75 Short-tailedShearwater Black Storm-Petrel

? 25 •_

JFM S OND

Figure2. The occurrenceof pelagicspecies off Californiaeach month compared to their nestingcycles at respectivebreeding sites. The latter informationis taken 40 SEABIRD OCCURRENCE

1972, report surfacewater temperaturestaken daily at shorestations from PugetSound to La Jolla. Somestations also collected daily salinity samples,as reviewedin Table 4. Data Reports, for temperatureand salinity,give the meanand its standarddeviation, the range,and the samplesize for eachmonth, and alsothe meanand the maximumand minimumfor the year. In someyears for somestations an insufficient number of observations were made for derivation of a valid mean, but maxima and minima were often reported. Thesedata were analyzedin two ways. First, the annualtemperature and salinity cyclesat eachstation were determinedby examiningmeans

Sabine's Gull 25 ?•

Wilson's Storm-Petrel Black-legge••

Blue-footed Booby

MarbledMI urrel[•l•I • I I I I

I-- 75' MagnificentFrigatebird Ancient Murrelet Z L•

Red-billed Tropicbird

Xantus'I Murrele••i IllI I I I 7525]•d$kua FM•• M• __ Aukl• d__Rhinoe•r•sFM A Md dA SO N D from Ainley et al. 1974; Bent 1919, 1921, 1922; DeLong MS; Drent and Guiguet 1961; Murphy 1936; Palmer 1962; Richardson 1961; Sealy 1974; and Serventy et al. 1971. 41 SEABIRD OCCURRENCE and rangesfor the 17 years(Figures 5 and6). Exceptfor temperature records from the Farallones, data are unavailable for 1973. There were no 1955 data, but hydrographicallyit wassimilar to 1956 (Reid et al. 1958, Bolinand Abbott 1963). This analysisgives a generalcomparison of hydrographicconditions among areas and seasons.Second, for each of the stations,the yearly means,maxima and minima were plotted (Figure 7). Data for Avila were too incompleteto include. The de- greesto which yearly meansand yearly mean maxima and minima dif- fered from the 17-year meanswere summarizedin Figure 8. These analysesallow comparisonof yearly variationsin hydrographicconditions. The relationshipbetween the water temperaturesrecorded at these shorestations to those farther offshorewas determined by comparison with isothermmaps preparedmonthly by the U.S. CoastGuard, Radia- tion Thermometer Program. General comparisonsof these data are presentedbelow for eachof the five censusareas.

Black-footed Albatross Sooty Shearwater N N

z uJ r•' I LaysanAlbatross

o iLirt-tailed Shearwater1 i i I I I I I I I I I I

Northern Fulmar N

z•-S

I i i i I I I i I I i I o n- IaJ I Pink-footedShearwater • Buller'sShearw•

] I I [ I I I I I I I I J ' F'M'A'M'J '•' A'S'O'N'D' J FMAMJ JASOND

42 SEABIRD OCCURRENCE

Bolin and Abbott (1963) and Abbott and Albee (1967) compare yearly differencesin phytoplanktonvolumes for MontereyBay, in central California. These authors felt that conditions in Monterey Bay gavean index to generalconditions in coastalwaters the lengthof Cali- fornia. As shownbelow, thesedata helpedexplain yearly differences in bird numbers. While marine birds do not feed directly on phytoplankton, the latter are at the baseof the birds' food web. Higher in the web are the zooplankton and some marine birds do eat some of them. Smith (1971) mapped zooplankton volumesin the California Current off Californiafor the years 1951 to 1966. His analysisis summarizedin Figure 9. Thesedata alsohelp explainyearly differencesin bird occurrence. The hydrographiccycle. The seasonalchanges in oceanographicconditions in coastalCalifornia presentedin fine detail by Bolin and Abbott (1963) are summarizedbriefly here. The seasonsin the area of their study, Monterey Bay, are indicative for the entire California coastal

NI Black-leggedI Kittiwakeß sl uJ z uJ Black Storm-Petrel n'N 1

o I I I I I I I I I I I • • NILeast Storm-Petrel N•l• ncient Murrelet zS

I I I I I I [ I i I I I

Xantus' Murrelet nNIzJ ISabine's Gull1 -- I J' F•M'A•MI J'J 'A 'S •O•N 'D • J•F•M•A'MIj•j 'A•S•O•N'D '

Figure 3. A comparisonof speciesoccurrence each month for areasnorth (N) and south (S) of Point Conception. 43 SEABIRD OCCURRENCE area,and are repeatedannually, but with differencesin the timing,in- tensity, and duration (Bakun 1973). There are also differences in de- gree and timing of the seasonsamong the censusareas. Thesedif- ferenceshave important bearing on the occurrencesof seabirds,as noted further in this paper. Threedistinct seasons are apparent in the annualhydrographic cycle of coastalCalifornia: the DavidsonCurrent period, the upwellingperiod, and the oceanicperiod. Thesethree result from the directionand strengthof prevailingwinds and resultant pattern of waterflow. During springand summerwhen northwest winds occur frequently, surface wa-

Black-footed Albatross Sooty Shearwater

LU Laysan Albatross Short-tailed Shearwater

<• Northern Fulmar Manx Shearwater

, . ,,,,, ß ß ß ....., i ! i ! ,i I.,. I.. Flesh-footed Shearwater Buller's Shearwater

• Pink-footed Shearwater Fork-tailed Storm-Petrel

, , , i i , i i , , I . 55 60 65 70 55 60 65 70 SEABIRD OCCURRENCE ter flowssouth and offshore to be replacedby nutrient-richwater from below(a processcalled upwelling). Temperatures reach the annuallow while salinitiesreach the annualhigh and then beginto slowlydecline.

Leach's Storm-Petrel Magnificent Frigatebird

0. ,;.;•!,!!;...!;,. Black Storm-Petrel Red-billed Tropicbird

i i i i i i i ....i i I i ,,,111i I i i ß ß i i i i i i i i i i i ! i • i i Least Storm-Petrel Skua I.I t1=,I,11,,,,11,, Wi Ison's Storm-Petrel Black-leggedKittiwake

i i i I i i i I i I i I ß I i i i i $

Brown Booby Ancient Murrelet

!11 ..... ,-,:' ...,•,!. Blue-footed Booby Xantus' Murrelet ...... I.... I..... !.,,,..,,!,!!II, 55 60 65 70 55 60 65 70

Figure4. Annualfluctuations in the abundanceof seabirdsin the coastalregion of California, 1955-1973. 45 SEABIRD OCCURRENCE

There is muchmixing of waterfrom differentdepths, and plankton productionis at its maximumrate. Duringthe following oceanic period, winds cease and southward water flow slackens to allow inshore and northwardflow of warmsub-tropical waters, normally displaced west- wardby the upwelledcold water. Temperaturesare at the annualhigh, salinityremains high, and phytoplanktonproduction is at the lowest levelfor the year. In the winter,with the strongsoutherly winds that ac.company storms, the Davidson Countercurrent moves northward close

14 C.MENDOClNO AVILA

20 I0 12• 2218

14 z S. BARBARA tu FARALLONES 20' • 16 .. 181

::) 16 I-"' 14.12 • 14. ,,, I0

! ! !

LA JOLLA 22: ,OVE

14 12 14;

JFMAM J JASOND

Figure5. The seasonalpattern of changein watertemperature for the different study areas. Shownfor a locationwithin eacharea are the monthly means,mean maxima and mean minima calculated from data collected 1956-1972 (Scripps Institution of Oceanography). 46 SEABIRD OCCURRENCE

C.MENDOCINO PACIFIC GROVE

34 34

z ! ! ! ! ! ß I ! ß ! ß

34 b.I

FARALLONES • 34

•1• I•1• I•1•J • • • • I• [• JFMAMJJASOND

Figure6. Theseasonal pattern of changein watersalinity for the different study areas. Shownfor a locationwithin eacharea are the monthlymeans, mean maximaand mean minima calculated from data collected 1956-1972 (Scripps Institutionof Oceanography). 47 SEABIRD OCCURRENCE to the coast. Plankton productionis low, surfacesalinities reach the annuallow point becauseof runoff from winter storms,and temperaturesbegin to decline. A comparisonof the areasin Figure5 (alsosee Bakun 1973) reveals the hydrographiccycle .occurring later in the yearwith increasinglatitude. For instance,highest temperature (oceanic period) at La Jolla on the averageoccurs in August,but not until Septemberor October farthernorth. Thereis lessvariation in the salinitycycles latitudinally

FARALLONES

PACIFIC GROVE

------

SANTA BARBARA

25 LAJOLLA

,oJ: , , "- - ---

Figure7. Yearlyvariations of watertemperature around the mean,mean maximumand mean minimum in the studyareas, 1956-1973. 48 , SEABIRD OCCURRENCE

(Figure6). The lowestsalinities (Davidson Current period) are reached duringJanuary in areasI and 2, and in February-Marchin areas3-5. This latter phenomenonmay be connectedwith the more frequent and intense winter storms and the resultant river runoff in the northern areas. Warm ocean temperaturesprevailed during 1957, 1958, 1959, 1972, and to a lesserextent in 1963 and early 1973 (Figures7 and 8). Tem- peraturesduring these years were abovethe meanand the meanmaxima and minimafor the study period (Figure8). Valuesabove the mean minimaare someindication for poorupwelling, which is suggestedalso by the low phytoplanktonvolumes recorded in 1958, 1959 and pro- posedfor 1972 and 1973 (Figure9). The warmwater of 1957 wasac- companiedby substantialphytoplankton volumes, but the cold waters of the precedingmonths may have been related to this. Low zooplankton volumes (from Smith 1971) were recorded off California in 1958, 1961, and 1965 (Figure 9). The years1956, 1961, and 1962 standout

I-,• mean -- w :• min. la.I

LI.I• max. -- z mean

• + .• min.

Figure8. A summaryof temperatureand salinity anomalies off California,1956- 1972. Verticallines give a relativeindication of the numberof studyareas having conditionsabove or belowaverage. Rectangles indicate that conditionsare average. 49 SEABIRD OCCURRENCE as being particularlycold. The years1963, 1967, 1970 and 1971 are interestingin that they includedtemperature extremes at both endsof the scale. In particular,1971 had temperaturesreaching the highest and almostthe lowestextremes for the entirestudy period. In general, phytoplanktonvolumes were high duringyears having cold tempera- turesand low in yearswhen cold temperatures were not recorded.High- er zooplanktonvolumes also occurred in yearshaving cold temperatures, but the relationshipbetween phyto o and zooplankton volumes is not al- waysa clearlydefined one. The trendsin salinitydid not closelymatch those of temperatures (Figure 8). Anomaliesin mean salinitiesmatched those in mean mini- mumsalinities, indicating that the amountof rainfallwas probably an importantfactor. The years1958, 1965, and 1967 hadvery low salinities. Thesewere yearsof high or slightlyabove average temperature anomalies,too, but high salinitiesoccurred in 1962-64 which included both coldand warmyears. Salinityanomalies tended toward the high end of the scaleduring the middleof the studyperiod, while prior to this, anomalieswent to both sidesof the scalewith a highincidence of averageconditions. During the period 1968-70, salinitieswere at the highand 10w extremes, interestingly, when temperatures were also chang- ing toward extremevalues. Duringthe last two warm years,salinities were "normal". The patternof salinityanomalies had no relationship to changesin phytoplanktonvolumes. Lowest zooplanktonvolumes occurredduring 1958 and 1965, alsoyears of lowestsalinities.

ß ß ß ß ß ß ß

PHYTOPLANKTON VOLUMES

ZOOPLANKTON VOLUMES

Figure 9. Relative phytoplankton(Monterey Bay only) and zooplankton(all California) volumesfor the years 1955-1966. Data were summarizedfrom Bolin and Abbott (1963), Abbott and Albee(1967) and Smith(1971). Phytoplankton volumesfor 1971 and 1972 are proposedon the basisof observationsmade at the Farallones(florimetric analysis; PRBO unpubl.). The Montereyand Farallon data are not preciselycomparable but both serveas general indices for the central coastregion, and possiblyfor a muchgreater region (Bolin and Abbott 1963). 50 SEABIRD OCCURRENCE

SPECIES ACCOUNTS

BLACK-FOOTED ALBATROSS (Diomedea nigripes). Black-footed Alba- trosseswere observedin all months of the year, but were most abundantJune throughAugust, the upwellingperiod (Figure 2). Numbersincreased during late May coincidentwith departureof adultsand fledglingsfrom their nestingislands in the HawaiianChain (Rice and Kenyon 1962). Individualsrecorded during the winter were presumablyprebreeding juveniles (Sanger 1970). Maximumabun- danceoccurred later in the year as latitude decreased:May-July in areas2 and 3 vs August in area 5 (Figure 3). This same trend in the entire easternPacific was alsoobserved by Sanger(1974a). South of centralCalifornia, numbers decreased (Table 3). High countsreached 220 birds off northern areasand 48 during one day's observationsoff southern California. Low abundanceat the Farallones (area 2) comparedto areas north and south probably resultedfrom a rarity of observationsbeyond the continental shelf. For instance, in April 1972, a few days after a trip reported 3-4 Black-footsnear the islands,I observed150 five km west of there, or about I km beyond the edgeof the shelf. The speciesseems to prefer deep waters,as noted alsoby Miller (1940). Kuroda (1955) recorded D. nigripeswhere water temperaturesranged 8 ø to 160C. This is roughlywithin the annualtemperature range found in northern and central California waters where in the present study they were most abundant. Large numbersof albatrossesoccurred during yearswhen temperaturesreached low levelsearlier in the year before most albatrossesarrived (Figures 4, 7 and 8). The low temperature,as an indication of intenseupwelling, suggests the likeli- hood for abundant food later on. Peak seasonalabundance (June-August) coincidedwith the non-breedingseason, the time of highestplankton volumes(Figures 2 and 9), and the period of risingbut not highesttemperatures. Interestingly, off WashingtonD. nigripeswas more abundantthan off Californiaduring August when temperaturesreached 16-18øC (Sanger 1970), temperatureshigher than those usually recordedin northern California (Figure 5). Sangerconcluded that, other factors being equal, higher temperatures were conducive to greater abundance of Black-foots. This seems true for California, too, but food abundance seemsa rather important "other factor" (Thompson1951). Excellentsummaries on the distribution and occurrenceof this speciesin the entire PacificOcean are givenby Robbinsand Rice (1974) and by Sanger(1974a). LAYSAN ALBATROSS (D. immutabilis). LaysanAlbatrosses were rarely seen in the study area, and were not recordedsouth of area 4 (Table 3). Recordsoc- curred February to April and August to October (Figure 3), the two periods describedby Sanger(1970, 1974b) and Fisher and Fisher(1972) for presenceof this speciesin the easternNorth Pacific. Comparisonof recordsduring this study with the speciesbreeding cycle in the LeewardHawaiian Islands, where adults are tied by nestingduties from Novemberto July, suggeststhat Laysansobserved off California in the springmust be mostly non-breeders(see also Sanger1970). Late summervisitors probably includesome adults as well (Fisher and Fisher1972). Kuroda (1955) remarkedthat Laysansavoid water above13øC in the western Pacific, and Sanger(1970) noted a similar tendency to avoid high temperatures. This may help explain the dearth of recordsfor southernareas where temperaturesare usuallyabove 13 *C, and the abundanceof recordsoff Washingtonwhere waters are usually colder. However,the years since 1955 during which D. im- rnutabiliswas recordedin this study were all of abnormallywarm water: 1958, 1967, 1971 (fall), and 1973 (summer)! Five of thesesightings occurred during the springwhen temperatureswere closeto 13øC (warm for Californiawaters at that time of year), but the three fall sightingsoccurred at or above160C (Figures 3 and 4). 51 SEABIRD OCCURRENCE

Sanger(1970) noted this speciesavoided water of relativelylow salinity (below 32%0),and Fisherand Fisher(1972) notedpreference for watersof relatively high salinity. Off California, the specieshas been seen most often during th4 early springwhen salinitiesare lowest(but still higherthan off Washington;see Sanger1970), and the four yearsin which it occurredhere had salinitiesat average or below. Sanger'sfurther. observation that oceanicwaters far from land are preferred by this speciesmay be more pertinenthere..In the four yearsof record, temperatureswere abnormallyhigh, probably a resultof alteredcirculation in the North Pacific (see Sette and Isaacs1960). Altered circulationpatterns, including the inshoremovement of oceanicwaters, may play a part in bringingLaysans into the study area (seealso Holmes1964). NORTHERN FULMAR (Fulmarusglacialis). Fulmarsbreed on the Aleutians and on islandsand coastsof the BeringSea (AOU 1957). They were reported throughoutthe Californiastudy area, but south of Point Conceptiontheir abun- dancedropped sharply (Table 3). Scatteredindividuals were seen during some summers,but usuallyfulmars were not seenconsistently or in any numbersuntil November. By then all birdshad left breedingsites. Peaknumbers off California were reachedlater in the winter as latitude decreased(Figure 2). In the Farallon area they were seen within 8 km of the coast, but were even more abundant westwardof the islands. April, the month of arrivalat the breedinggrounds (Bent 1922), wasthe first month of their generalabsence from California waters. Kuroda (1955) found fulmars commonestin cold waters (3-8øC), temperatures rarely reached off the California coast. Here, they seemedto be low in number during warm yearsand duringthe warmestpart of the summer;and most abundantduring winters of colderwaters, 1961 to 1971 (e.g. temperaturesaverag- ing near 9øC (Figures 2 and 4). They also were abundantduring years of high maximumsalinity anomalies, which might suggestan associationwith more oceanic waters during winter. Relativeto temperature,fulmars should have been abundant duringthe cold year of 1956, but this wasapparently not so. Interestingly, salinitieswere very low that year (Figure 8). Thus fulmarsperhaps prefer cold water of high salinity. FLESH-FOOTED SHEARWATER (Puffinus carneipes). Flesh-lootedShear- waters breed on islands near Australia and are uncommon off California; in fact, they seemto be nowherecommon at sea(Murphy 1936). They occurredoff the Californiacoast from May, just after the fledgingperiod, to early November,the period of arrival and prebreedingactivities at the nestingislands (Figure 2; see Serventyet al. 1971). The birds seenSeptember to Novemberare probably on their way southward. Kuroda (1955) consideredthis a "warm water species". His sightingsin the western Pacific occurred where water temperatureswere 110 to 16'C. Flesh- looted Shearwaterpresence off Californiaseems to agreewith Kuroda'sobserva- tions, as the speciesis more often seenin the southernregions (warmer waters) than northern ones (Table 3). If a water temperaturerange of 11-16'C is preferred,California waters should be ideal,for that is the normaltemperature range from May to November. Flesh-lootedShearwaters were not seenduring years of extremely cold temperature anomalies(1956, 1962, 1967), with the exceptionof 1971, when warm watersalso occurred later in the year (Figures4, 7 and 8). PINK-FOOTED SHEARWATER (P. creatopus). Pink-looted Shearwatersnest on islandsin warmer watersoff Chile and spendthe interim periodsin the eastern North and South Pacific (Murphy 1936). They were commonin all partsof the study area from April to November, although sightingswere more frequent from August to early October (Figure 2). This is essentiallythe non-breedingseason. They have occurredas far north as Alaskain someyears (Murphy 1936), but during this study they were much more abundant in southern regions (Table 3). 52 SEABIRD OCCURRENCE

There was a direct correlationof yearly abundanceto meanmaximum temperatures at La Jolla (P<0.05, r=0.62, z=2.48; SpearmanRank Correlation).Thus off Californiathey seemto preferwaters in the upperrange of temperatures. Yearly differencesin abundanceoff California may alsobe connectedto ocean conditions off Peru and Chile, where Pink-foots are known to occur in all seasons (Murphy 1936). The trends in Pink-foot populationsoff California (Figure 4) are the reverseof seabirdpopulation trends, including shearwaters, off Peru(Idyll 1973; Jordan 1967). These Peruvianpopulations were low during the period 1957-59, were high 1960-64, and have been low ever since. The first depression resultedfrom a disappearanceof anchoviesdue to oceanographicconditions ("El Nifio"; see Murphy 1936), and the secondby a disappearanceof anchoviesap- parently causedby human over-fishing. During periodsof low anchovypopula- tions, Peruvianseabirds die or dispersefarther than usual(Murphy 1925, 1936). During those lean years, P. creatopusmay move in greaternumbers to the Cali- fornia Currentregion. This may, of course,be speculative. SOOTY SHEARWATER (P. griseus). Sooty Shearwatersat peak abundance were by far the most numerousbird in the study area, and probablynumbered more than all other speciescombined. Those occurring in Californiawaters prob- ablyoriginate from sub-Antarcticislands off both CapeHorn and New Zealandfor the followingreasons. First, P. griseushas been noted from BajaCalifornia south to the PeruCurrent (Loomis 1918; EASTROPACPrelim. Repts., T. J. Lewispers. comm.; observationsby T. J. Lewis pers. comm.; Jehl 1974). In that areabe- tween Peru and California,Sooties were equal in abundanceto Short-tailedand Buller'sshearwaters, species known to breedonly in the New Zealand-Australia area,but cruisetracks perhaps have not intersectedthe main north-southSooty Shearwatermigratory route. Second,King (1970) recordedSooties as abundant duringmigration in the areaimmediately east of the main HawaiianIslands. These were presumablybirds on their way betweenNew Zealandand the easternNorth Pacific. Third, Sooty Shearwatersbanded in the New Zealandarea have been re- coveredin Californiawaters (Richdale 1957, Warham1964). Theseclues suggest that Sooty Shearwatersoff California nest in both the New Zealand-Australia and the southernSouth America regions. Loomis (1918), Beck (1910) and Mur- phy (1936) suggestedthat most, if not all, Sootiesseen off California were from South America. They were not aware, however, of the vast numbers of this speciesnesting in sub-AntarcticNew Zealand (see Richdale 1963). SootyShearwaters were most abundant off Californiafrom mid-Maythrough September(Figure 2). Highestnumbers were presentin July and August,the periodof maximumproductivity in thesewaters as well asthe birds'non-breeding season. Sootieswere abundantoff southernCalifornia only in May (Figure 3). They prefer colder waters (Murphy 1936; Kuroda 1955), and might avoidthat area when temperaturesbegin to rise in followingmonths. Their abundanceas earlyas May, so soonafter the nestingseason, suggests that manyfly directlyto Californiarather than, as Phillips(1963) and othershave proposed, by circum- navigatingthe North Pacific. King (1970) noted they migrateon a broadfront acrossthe tropical centralPacific, a fact that supportsdirect flight to California by at leastpart of the New Zealandpopulation. Yearly differencesin abundancein this regionwere not clearlydefined, per- hapsdue to the nature of the data. Most evidentwas their scarcityduring the warm water yearsof 1957, 1958, 1966-67, and 1972-73 (Figure 4). SHORT-TAILED SHEARWATER (P. tenuirostris). Short-tailed Shearwaters breed on islandsin the Australianregion and duringthe non-breedingseason in- habit watersof the far northernPacific (Kuroda 1955, Marshalland Serventy 1956) and BeringSea (Bartonekand Gibson_1972).They were observedin very smallnumbers off Californiamostly during the late fall (peak in mid-November)

53 SEABIRD OCCURRENCE

and winter (Figure 2), but not in all years. Comparisonof their pattern hereto their nestingcycle suggeststhat individualsreported off Californiawere mostly non-breeders.After a month or more of pre-breedingactivities, they lay eggs over only a three-weekperiod beginningin late November(Serventy et al. 1971). Short-tailsseen off California after early Novembermay includethose pre-breeding juvenilesthat visitthe nestinggrounds during or after egglaying. Kuroda (1955) found little correlationto water temperaturein the occurrence of P. tenuirostris off Japan or in the North Pacific. He noted them in waters 3.5 ø to 12.5 øC, the cold end of the scale in California. Greater numbers occurred here when water temperatureswere cold during the fall and winter or when up- wellingseemed strong earlier in the year, indicatinga greaterlikelihood for abundant food (Figures 4, 7 and 9). A changein occurrencewith latitude off Cali- fornia was not apparent(Table 3). MANX SHEARWATER (P. puffinus). Manx Shearwatersbreed on islandsoff the west coast of central Baja California, and many seemto remain in that area the year round (AOU 1957, T. J. Lewis pers. comm.). They became common in the study area during December,which is the midst of the DavidsonCurrent period and the end of their non-breedingseason (Figure 2). They occurredabun- dantly off San Diego and lessso as far north as Monterey, but sightingsdropped sharply north of there (Table 3). They have been reported rarely as far north as Vancouver (AOU 1957). Greatest yeafly abundance and extensive northward movementoccurred during years when water temperatureswere aboveaverage off San Diego, years when temperatureswere high farther north as well (Figures4 and 7). In fact, abundancecorrelated directly to mean maximum temperatures at La Jolla (P<0.01, r=.71, z=2.84; SpearmanRank Correlation). Such conditions of high winter temperaturesindicate strongnortherly flow of Davidson Current waters. Manx Shearwatersthus seemto prefer waters 14øC and above the year round. BULLER'S (NEW ZEALAND) SHEARWATER (P. bulleri). Buller's Shear- waters breed on the temperateNorth Island of New Zealand. They are most numerous off California from eariy Septemberto early October, the time when adults begin to arrive at nestingareas (Figure 2; Serventyet al. 1971). During their period of greatestnumbers off California,birds were often seenin rapid flight,suggesting they werein the midstof migratorymovement. Their abundance decreasedrapidly south of Monterey (Table 3), and few havebeen reportedin the easternPacific south of Baja California (EASTROPAC Prelim. Repts., T. J. Lewis pers. comm.). Birdsoccurring off Californiaprobably turn towardsNew Zealand at about the latitude of central California. Kuroda (1955) found them most abundant in the western North Pacific at the boundaries between warm and cold currents. Ocean temperatures were 14.5- 16øC, the normal upper rangein temperaturesfor northernCalifornia. P. bulleri was most abundant off California during three fall periods:1956, the year pre- cedingan intensivewarm water periodand a year of strongupwelling and abundant plankton; 1966 and 1967, years of aboveaverage fall oceantemperatures, of aboveaverage upwelling, and highplankton volumes; and 1970 and 1971, years precedinganother warm periodand yearsof aboveaverage upwelling and plankton volumes. During the birds' presence,isotherms were closelyspaced and close to and parallelto the Californiacoast, indicating that the boundaryof cold inshore waters and warm waters was close to the coast also. Occurrence in the study area under these conditions was thus in agreementwith Kuroda'sobser- vations. Buller's Shearwatersoccurring in high numbersoff California seemto foretell a periodof warm water to follow. FORK-TAILED STORM-PETREL (Oceanodrornafurcata). Fork-tailed Storm- Petrels breed on islands from the Aleutians south to northern California (AOU

54 SEABIRD OCCURRENCE

1957). They were uncommon the year round from central California (area 3) north with no seasonalchange in abundance(Figure 2). This may indicatethat the birds in the study area were mostly non-breeders.They were presentin the southernareas only during the springand fall, and in area 5 only one bird was seenduring the study period (Table 3). According to Kuroda (1955) and to Martin and Myres (1969) the speciesin- habits cold waters. Kuroda found them most abundant in waters 3-8øC and saw scatteredindividuals in warmer waters. The fact that only "scatteredindividuals" are seen off California is probably related to waters being warmer than 8øC; and rarity of this speciesin area5 is probablydue to their avoidanceof the very warm waters there. Numbers have varied little in the study area, but they were most abundant during the spring of 1970 and 1971 and the fall of 1973, periodsof unseasonallycold waters(Figure 4). LEACH'S STORM-PETREL (0. leucorboa). Leaoh's Storm-Petrels breed on offshoreislands and headlandsfrom Alaskasouth to centralBaja California (AOU 1957). Only white-rumpedforms were recordednorth of Point Conception,but both these and dark-rumpedindividuals, with the latter predominating,occurred south of there. Much information has been lost by observersand editors not re- porting the two forms separately. Distinguishingdark Leaoh'sfrom other dark storm-petrelsin the easternNorth Pacific on the basisof sizeand color is usually difficult (Crossin1974), but flight characteristicsare distinctbetween most species,and are particularlyevident when mixed speciesflocks are observed(Stallcup pets. comm.). They were very abundant off southernCalifornia in comparisonto areas1-3 (Table 3). The Farallon populationis much smaller(ca. 700 pair; Ainley and Whitt 1973, Ainley and Lewis 1974) than populationsboth north and south, which helps explain the fewer numbersseen in northern study areas. The fall peak in numbers,especially in northern areas,corresponds well with the fledging period at the Farallones(Ainley, Morrell and Lewis1974). Birdscollected during the fall over the years off central and northern Californiaand depositedin the Museumof VertebrateZoology (MVZ) and California Academyof Sciences(CAS), are almost all fledglings,based on characteristicsof molt (Ainley, Lewis and Mor- rell 1976), as were 15 individualsfound dead on area 4 beachesduring fall 1973 (Ainley unpubl.). Martin and Myres(1969), Ainley et al. (1974) and Sanger(pers. comm.) report that from Californianorth to BritishColumbia the speciesprefers warmer oceanic waters, i.e. those westward of the California Current in the Cali- fornia region. This alsohelps explain low numbersin northernstudy areas,where warmer waters occur far offshore, and their greater occurrenceduring the fall when warm oceanic waters move closer to the coast. Fall also is the period for fledglingswhich may stray from the adult norm (Figure2). In the westernNorth Pacific, Kuroda (1955) noted O. leucorboain warmerwaters than those preferred by O. furcata, a phenomenonalso noted by Martin and Myres (1969) and Sanger (pers.comm.) for the easternNorth Pacific. High abundancein the study areasoccurred in some years when waters were warm, in some when upwelling was strongearlier, and in otherswhen salinities were low (Figure 4). This last factor, if a result of stormsand heavy rain runoff, might indicate that the large numbersin thoseyears represent birds concentrated near the coast by the storms. The 1973 peak did result from such conditions. Fewer Leaoh's Storm-Petrelswere seen during years when ocean temperatures were cool. ASHY STORM-PETREL (0. bornocbroa). Ashy Storm-Petrelsbreed from Los Coronadosnorth to the Farallonesand Point Reyes (AOU 1957, Ainley and Osborne 1972). They were observedat all times of the year in waters off central California, and peak numbersoccurred from Septemberto October when they 55 SEABIRD OCCURRENCE concentratedin Monterey Bay (Figure 2). This peak coincidedwith peak fiedg- ing at the Farallones,where the 4000 bird breedingpopulation (Ainley and Lewis 1974) probablyoutnumbers all other of this species'breeding populations combined. Ashysvisit the Farallonesyear round. Fall concentrationsin Monterey Bay probablyincluded Farallon breeders, non-breeders, and fledglingsalong with individualsfrom southernpopulations. This would seemlikely, judgingfrom the high estimatesof birds there (up to 7000). A generalnorthward movement of storm-petrels,including several species, seems to occureach fall in the study area. About half the specimensin MVZ and CAS, collectedover the yearsduring the fall in MontereyBay, are birds-of-the-year.Scattered Ashys in the fall sometime reachas far north as CapeMendocino (Table 3). Ainley et al. (1974) describe them asbeing restricted to the coastalarea of the CaliforniaCurrent from northern BajaCalifornia to CapeMendocino. Yearly differencesin abundancewere not analyzedbecause the fall concentra- tion area in MontereyBay wasdiscovered a few yearsago, and this stronglybiases numbersfor later years. BLACK STORM-PETREL (0. melania). Black Storm-Petrels breed on islands off the east and west coastsof central and northern Baja California (AOU 1957). They were observedoff Californiaduring most months,but with increasinglatitude, they occurredmore frequentlyin the fall (Figures2 and9). North of area 3, O. melania was observedvery rarely, but severalthousand were presentin MontereyBay duringthe fall of certainyears (Table 3). The fall peak,September to October,corresponded to the late fledgingand post-fledgingperiods and to the oceanicperiod, the time of warmestocean temperatures. Greatest numbers occurredduring years of aboveaverage fall oceantemperatures (Figure 4). Yearly abundancecorrelated directly to mean maximumocean temperatures at La Jolla (P<0.05, r=.51, z=2.04; SpearmanRank Correlation). A steadyincrease of fall numbersin Monterey Bay over-•-hepast severalyears relates well to the pattern of risingfall water temperaturesthere (Figure 7). Duringyears of colderwaters, this specieswas mostly absentfrom the study area. Black Storm-Petrelsthus seem restricted to warmer coastal waters (ca. 16' and above) throughout its an- nual cycle.

LEAST STORM-PETREL (Halocyptena microsoma). Least Storm-Petrels breed on many of the same islandsas the previousspecies (AOU 1957). Their presenceoff California was restrictedto Septemberand Octoberexcept in area5 where they also occurred in low numbersduring July and August (Figure 2). They were presentlater in the fall with increasinglatitude (Figure 3). North of Point Conception,they were seenrarely (Table 3). During 10 of 19 years in this study, they were not reportedeven in area 5. Peak seasonalabundance corresponded to the oceanicperiod of maximum temperatures.These petrelswere reportedonly duringyears whentemperatures at La Jolla were at or aboveaverage maximum (23.1'C). Duringthe periodsof their greatestabundance, fall 1970 and 1971, temperatureswere the highestre- corded for the study period, 24-25'C at La Jolla.

WlLSON'S STORM-PETREL (Oceanites oceanicus). Wilson's Storm-Petrels occurring in the eastern Pacific breed in the Cape Horn region (Murphy 1936). They were recordedrarely duringthis study, and all 10 recordsoccurred between mid-Augustand the first day of November(Figure 2). Adults shouldhave begun visits to the breeding islandsby early November, so possiblythese 10 birds were pre-breedingjuveniles. It may be significantthat nine of the recordswere during years of disruption in fish populationsof the Peru Current, where O. oceanicus usuallywinters (Murphy 1936).

56 SEABIRD OCCURRENCE

MAGNIFICENT FRIGATEBIRD (Fregatamagnificans). Magnificent Frigate- birds breed in the tropics (AOU 1957). They occurredoff California from late June to early November(Figure 2), suggestingthat in comparisonwith a rather ex- tendedperiod of nest attendance,individuals seen were mostly non-breedersbut not fledglingsof that year. In other words,breeding adults should still havebeen attendingyoung when the speciesoccurred in Californiafar from the nearestbreed- ingsite (Magdalena Bay, southern Baja California). Most frigates seen in California are indeedjuveniles (McCaskie 1970); however,immature plumage is retainedfor severalyears (Schreiberpers. comm.). Numbersand frequenciesof recordsde- creasedsharply with increasinglatitude, particularly north of areas4 and 5 (Table 3). This couldbe relatedto increasingdistance from nestingareas, but more probably is connectedwith decliningocean temperatures. Peak seasonalabundance occurred in July and August, coincidingwith the period of maximum water temperaturesin southernareas. Frigatebirdswere presentduring yearswhen temperatureswere near to or abovemaximum and were absent in cold or moderateyears. Except for one record in 1968, they were seennorth of Point Conceptiononly duringyears of unusuallywarm conditions, i.e. temperatures17-18øC or more (Figure 4). The largestnumbers occurred during1972, a year of warmwater and a year followingone in whichbreeding successwas very high in Baja colonies(D. W. Anderson pers. comm.). These facts suggestfrigatebirds move north in sub-tropicalconditions, and occurrence off Californiadepends on the presenceof theseconditions. BROWNBOOBY (Sulaleucogaster). Brown Booby is a sub-tropicaland tropical breeder (AOU 1957) which rarely occurs in California. All records were southof Point Conception(Table 3) and were in February,June-September and December. Seasonally,their occurrencegenerally coincided with warm temperatures, and they occurredin warm years (Figure 4). Three recordswere apparent- ly of the sameindividual that visited San Miguel Islandduring the summersof 1961, 1965 and 1968 (McCaskie 1970). BLUE-FOOTED BOOBY (S. nebouxii). Blue-lootedBooby, anothersubtropi- cal breeder (AOU 1957), was rare in California. Individualsof both booby species occurringin Californiaprobably originate from nestingareas in the Gulf of Cali- fornia or coastalMexico. All occurrencesof Blue-footswere after the fledging periodwhich, along with plumagecharacters (see McCaskie 1970), indicatedyoung birds(Figure 2). All recordswere from Augustto November,the time of highest oceantemperatures. Only in the abnormallywarm fall of 1971 did this species reachas far north asPoint Conception and Monterey(Table 3; Figure4). RED-BILLED TROPICBIRD (Pbaetbon aetbereus). Red-billed Tropicbird, another tropical pelecaniform,probably arrived in Californiawaters from the Revilla GigedoIslands or islandsin the Gulf of California. Sightingsof this bird decreasedrapidly with increasinglatitude (Table 3). They were seenseveral times in area 5, three times in area 4, and once in area 3 (Monterey Bay region). The speciesreportedly breeds year-round in the Gulf of California (Palmer 1962), but it occurredoff southernCalifornia from May through October, with highest numberspresent from August to October (Figure 2). The pattern coincidedwith movementof warmer oceanicwaters into the studyarea. Tropicbirdsusually occurredduring periods of extremeconditions-years having very cold waters(1956, 1962, 1969, 1970 and 1971) and years of warm waters (1957, 1959, 1971 and 1973). Interestingly,like Buller'sShearwaters, they were most abundantin the study area prior to warm water periods (e.g. 1956, 1968-70), but they became lessplentiful duringthe warm years(Figure 4). They occurredin yearsof strong upwelling. Occurrenceof tropicbirdsin Californiawaters may be relatedto move- ments of tuna schoolswith which they are often associated(see Ashmole and Ashmole 1967). Williams(1972) and Fink and Bayliff (1970) describedseasonal 57 SEABIRD OCCURRENCE movementsof SkipjackTuna (Katsuzvonuspelamis) into the easternNorth Pacif- ic. Tuna begin to occurnear the RevillaGigedo Islands in April, moveinshore off BajaCalifornia during May andJune, and reach their northernmost extent off northern Baja and sometimessouthern California in Septemberbefore turning south. There is goodagreement between this patternand that for tropicbirdsin the southernstudy areas. A slightlymore northernmigration of tuna in certain yearswould readilybring tropicbirds to our area. In fact, duringthe elevenyears from 1955 through1965, the greatesttonnage of tuna caughtnorth of 15øN alongthe Baja Coastwas in the four-yearperiod 1956-59 (Josephand Calkins 1969), a periodof many tropicbirdrecords off SanDiego (Figure 4). SOUTH POLAR or CHILEAN SKUA (Catbaracta maccorrnicki or C. cbilensis). Most skuasseen off Japan,according to Kuroda(1955), are South PolarSkuas, and it is generallyfelt that this speciespredominates in Californiawaters, too (DevillersMS). It would not be surprisingif someoff Califomia were Chilean Skuas,since other mobile speciesof the Peru Current also visit here regularly. ChileanSkuas have been reported as far north as northernPeru (Murphy 1936). Skuaswere seenoff California during most months,but the majority of records were in Septemberand October(Figure 2). Both speciesbegin egg laying in November(Murphy 1936, Ainley pers. obs.), the South Polarabout 2-3 weeks later than the Chilean, and both arrive at the nestingarea a month beforehand. Most California records occurred when these birds should have been present at breedingareas, indicating that Californiabirds are non-breeders.South Polar Skuasdo not return to nestingareas until age3 or more (R. C. Woodpers. comm.) but whetheror not thesejuveniles regularly wander the extent of the world's oceans is unknown. Withoutexception, highest numbers occurred during years in which phytoplanktonvolumes were highest (P<0.01, r=.81, z=2.83;Spearman Rank Correla- tion). Skuasdo not eat phytoplankton,thus the exact nature of the relationship is not clear. Low numbersoccurred during years of warmestfall temperatures (Figure4): 1958, 1959, 1966, 1967, 1972 and 1973 (early). Therewas no well- defined trend in abundance relative to latitude (Table 3). SABINE'S GULL (Xema sabini). Sabine'sGull breeds on the Alaskan tundra, becomespelagic during its migrations,and winters off Peru(Murphy 1936). In late April andearly May, Sabine's Gulls passed through the studyarea very quick- ly, asindicated by the well-definedpeak in numbersat thattime (Figures 2 and.3). The fall passageextended from late Augustto earlyOctober, but mostpassed southin mid-September.These periods coincide closely with arrivaland depar- ture at the breedinggrounds (Bent 1921), anotherindication of fastmigration in this species.Yearly differences in abundancecould not be analyzedbecause of insufficientquantitative data. The specieswas reported most often in area 5 (Table 3). BLACK-LEGGED KITTIWAKE (Rissatridactyla). Kittiwakes breed on the rocky cliffs of the AleutianIslands and of islandsand headlands further north (AOU1957). Theyare pelagic during the winterin ourarea, with highest numbers reportedfrom Montereysouth (Table 3). Theywere seen earlier in the fall in northernareas, but did not becomeabundant anywhere in the regionuntil late December,well after the breedingseason (Figures 2 and 3). Both thesefactors indicatea leisurelymovement. Peak numbers were present late February to early March,possibly as birds were massing for northwardmigration, but also possibly becauseof watertemperature (see below). Departurefrom Californiawas about a month beforeexpected arrival at nestingareas. Kuroda (1955) found them most abundantwhere waterswere 5-6øC, temperatures far lower than those in California waters. Greatest abundance here did not occurduring the coldestmonths, but whenwater temperatures were 9-16øC. 58 SEABIRD OCCURRENCE

During years when winter temperatureswere at or below average,kittiwakes were more abundant;and in years of above averagewinter temperatures,they were few in number (Figure 4). THICK-BILLED MURRE (Uria lornvia). These murres breed on the cliffs of islandsand headlandsof the high Arctic (AOU 1957). Nine individualswere seen on six scatteredoccasions in Monterey Bay. No obviousrelationship of their oc- currenceto oceanographicconditions was evident. They could be easily over- lookedin area2 amongthe thousandsof CommonMurres (Uria aalge)there. HORNED PUFFIN (Fratercula corniculata). Thesepuffins breed on British Columbian,Alaskan and BeringSea islands (AOU 1957, Drent and Guiguet1961). Twelvewere recordedduring six yearsof the study,within all five areas. Similar- ly to the juvenileKittlitz's Murrelet(Brachyramphus brevirostris), another Arctic speciesfound at La Jollaon 16August 1969 (Devillers 1972), Horned Puffins oc- curredMay to August,but mostly during the late summer. That is when oceanic waters move closer to the coast. No other correlations to ocean conditions were apparent. Most puffins, and U. lornvia, too, were reported in 1972 and 1973, both years of anomalousconditions. Hamilton (1958) recordedboth speciesas common far south of the Aleutian Islands,and Clapp and Woodward (1968) recorded Horned Puffins in Hawaii! It might well be that these arctic speciesare much more abundant than suspectedin oceanicwaters west of the California Currentduring some years, and that it takesanomalous conditions to bringthem coastward. ANCIENT MURRELET (Synthliboramphusantiquus). Ancient Murrelets breed on coastal islands off British Columbia and southeastern Alaska (AOU 1957). They winter throughoutthe study area, but mostly north of area 3 (Table 3). Greatest abundance occurred from late November to early March, indicating southwardmovement well after nesting(Figure 2). They may wait for ocean temperaturesto cool down here, or for stormy weatherto beginfarther north. Departurefrom Californiaoccurs suddenly just beforearrival at breedingareas. Kuroda (1955) noted this speciestwice off Japan at ocean temperatures4.5- 5.5øC. Off Californiatheir greaterabundance in northern areasand during winters of low water temperatures(near 9øC at the Farallonesand 10uC at Pacific Grove;Figure 4) indicatesa preferencefor colderwaters. MARBLED MURRELET (Brachyramphusmarmoratus). Marbled Murrelets breed along the coast from southeasternAlaska to the northern part of area 3 (AOU 1957). Numbersfell sharply south of Point Conception(Table 3). They were reportedyear-round except during May and June(Figure 2), whenadults are supposedlyon eggsor feedingchicks (Sealy 1974). They may be lessvisible to shoreobservers during that time, but A. Baldridgeand R. Stallcup(pers. comm.) have often observedpairs in breedingplumage during May and June off Pigeon Point (area 3). XANTUS' MURRELET (Endomychurahypoleuca). Xantus' Murrelets breed on islandsin study areas4 and 5, and farther south along the west coastof Baja California (AOU 1957). Occurrencedeclined graduallywith increasinglatitude (Table 3). They were presentyear-round in areas4 and 5, but only during the springand fall farther north (Figure3). With all areascombined• most records were in early March, just before egglaying, and in August,just after the last chicks fledge (Figure 2). Greatest abundancewas in yearswhen late summerand fall ocean temperatureswere above averagemaximum (Figure 4); yearly abundance correlated directly to mean maximum temperaturesat La Jolla (P

MARINE BIRDS AND THE ENVIRONMENT

The relationshipof marine bird distribution and occurrenceoff Cali- fornia wasmost clearlydefined relative to oceantemperature, and less clearly so relative to salinity. One factor involvedhere was that tem- peraturefluctuation was greater and more clearly defined. Murphy (1936) felt that temperaturewas critically important in any explana- tion of seabirddistribution. Sanger (1970), for certainspecies off Wash- ington, noted somecorrelations to salinity, but referredto almosttwo- fold differencesin concentrations,a range not notedin the present study. Water temperaturesrelate to bird occurrencein two major ways. First, they are an index to the strengthof upwellingof cold, nutrient- rich waters, and hence, an index to food abundance at the base of the food web (seeBolin and Abbott 1963). Good phytoplanktonproduction usuallyoccurs in cold, nutrient-richupwelled water. After that the relation to marine birds becomescomplex and not well understood,except that largenumbers of marinebirds also occur in productivewaters (Murphy 1936, Ashmole 1971). Food abundance, however, is not necessarilythe sameas food availability, but it too correlatesto ocean temperature. For example, Northern Anchovies(Engraulis mordax), one of the major food items for California seabirds(PRBO unpubl. data), remainin deep waterswhen temperaturesare warmand thus are not availableto seabirds(Frey 1973). 6O SEABIRD OCCURRENCE

The secondway in which temperatureaffects the numbersand species of seabirdsrelates to the temperaturepreferences of the species. In the northernNorth Pacificeach water massor oceanographicregion, defined by physicalfactors at certain values(Dodimead et al. 1963), hasa particularmarine bird communityassociated with it (Sanger1972). Murphy(1936) discussedthis for SouthAmerican waters. The phenomenon is well establishedfor other California marine biota (e.g., Bolin and Abbott 1963, Hubbs 1963). Hubbs mentioned marine birds in his review of the phenomenon,but observationsin the presentpaper re- vise his observations. For instance, he discounted the occurrence of boobies off California. In coastal waters south of Point Conception, where temperatures usuallyrange 13' to 16'C at the springlow and 16.5' to 23'C at the late summerhigh, the typical marineavifauna includes breeding species aswell as visitors. Except for BrownPelicans (Schreiber and Risebrough 1972) and Double-crested Cormorants (Pbalacrocorax auritus; Gress et al. 1973), current information on other breedingspecies exists only for relativelysmall breeding communities, e.g. offshorerocks (Osborne and Reynolds 1971) and Santa BarbaraIsland (Hunt and Hunt 1974, PRBO MS). These speciesat present (AOU 1957, Ainley and Lewis 1974) include three storm-petrels(0. leucorboa,melania, and bomocbroa),pelicans,three cormorants(P. auritus,penicillatus, pelagicus), Western Gulls (Larusoccidentalis), and three alcids(CeplVbus columba, Endomycbura bypoleuca,and Ptycborampbusaleuticus). Three of thesedo not breed north of the point, but four northernbreeding species do not presently breed south of the point (0. furcata, Uria aalge,Lunda cirrbata, Cero- rbinca monocerata; see below). The usualvisiting species in coastalwaters south of Point Conception are from springinto the fall: Black-footedAlbatross, Flesh-footed, Pink- footed, and Sooty shearwaters,and Black Storm-Petrel. Under particularly warm conditionsin the fall, MagnificentFrigatebirds, boobies and Least Storm-Petrels occur, and under cool fall conditions, Short-tailed Shearwatersmay occur. The typical winter visitors are Manx Shear- water and Black-leggedKittiwake, but when cooler conditionsprevail then fulmars,murres and Ancient Murreletsvisit in larger numbers. In coastalwaters north of PointConception, where temperaturesnor- mally range9* to 14'C at the springlow and 10.5' to 16'C at the fall high, the typical marine avifauna includes the breedingspecies (see aboveparagraph, Ainley and Whitt 1973, and Marbled Murrelet account above) as well as severalvisitors. In spring,summer and early fall these are: Black-footed Albatross, Flesh-footed, Pink-footed, and Sooty shearwaters, and Fork-tailed Storm-Petrel. Buller's Shearwateroccurs only in the fall. If upwellinghas been poor duringearly spring,these species do not occur in usual numbers. In late fall and winter the visitors are.-

61 SEABIRD OCCURRENCE

Northern Fulmar, Common Murre (U. a. inornata from northern breeding areas;Storer 1952, Smailet al. 1972), AncientMurrelet, Rhinoceros Auklet (a rare breederin thisarea, too), and Black-leggedKittiwake. If winter temperaturesare warmerthan normal,these species are usually scarce. If fall temperaturesare unseasonallycold, Short-tailedShear- waters occur also. When conditionsare unduly warm, speciestypical of waterssouth of PointConception move north. Theseinclude, usually, Manx Shearwater,Black Storm-Petrel, frigatebird and Xantus'Murrelet. Under extremelywarm conditionsboobies and LeastStorm-Petrels also move north. Extensiveoverlap thus occurs in visitingmarine avifaunas of northern and southernCalifornia during the upwellingperiod. The upwelling and southwardmovement of cold water affects the overlapby unify- ingmarine conditions. When the oceanicperiod approaches in southern Californiathe extent of overlapdecreases and subtropicalmarine birds occur there. However,if oceanicperiod temperatures are abnormally warm in northern areasthen many of these speciesmove north of Point Conceptionto againproduce extensive overlap. Species composi- tion seemsless variable from year to year duringthe DavidsonCurrent period. If coldertemperatures occur during winter, indicating possibly a weak countercurrent(Bolin and Abbott 1963), then northern species move south of Point Conceptionin greaternumbers. A strongcounter- currentseems to bringthe subtropicalManx Shearwaternorth.

SEASONAL CHANGES IN NUMBERS AND SPECIES DIVERSITY

The number of marine bird speciesvisiting California'snearshore watersis lowest during March and April, increasesto a peak in Septem- ber, and then declinesthrough the winter (Figure 10). Numbersof individualsfollow a similar pattern (Figure 2). Numbersand species diversitybegin to increaseduring the upwellingperiod, reach their peak just before and duringthe oceanicperiod, and then declineduring the DavidsonCurrent period. Thesechanges are a functionof the breeding seasonsof respectivespecies, along with factorssuch as food availability and climate. That is, when the speciesfrom South Pacificnesting areas are passingthrough in migration (e.g. Buller'sand Flesh-lootedshearwaters) or are lingeringon while food is still apparentlyavailable (e.g. Sooty and Pink-looted shearwaters),species from subtropicaleastern North Pacificnesting areas are finishingtheir breedingand watersoff California are becomingwarm enoughto suit them. Thus, demand placed on the resourcesof coastalCalifornia by visitingmarine birds 62 SEABIRD OCCURRENCE increasesduring the upwelling period and reachesits peak in the early oceanicperiod. Demandon the resourcesof coastalCalifornia by residentbreeding speciesincreases and declinesin a patterntimed similarly to the visitors' (Figure 10). An intensivestudy on this phenomenonis now under way for the central California area (PRBO), and the following points are readilyevident. Duringthe upwellingperiod, breeding adults are raising young as well as feedingthemselves; and during the oceanicperiod or just before it, fledglingsgo forth on their first month or two of inde- pendence,supposedly the most critical in their future chancesof sur- vival (see reviewsin Lack 1968, 1972). Adults are still presentin coastal Californiathen, too. Thesecoinciding patterns of food demandby visitingand residentspecies are interestingin light of recentstatements about the role of interspecificcompetition in the evolution of feeding adaptationsand patterns of food resourceexploitation (e.g. Ashmole and Ashmole 1967, Pearson1968, Scott 1973, Cody 1973). Competi- tion for resourcesof the oceanamong all membersof marinebird communities has rarely been considered. If interspecificcompetition for food amongresident species can be so importantin shapingthe organi- zation of breedingseabird communities,what is the effect on this or- ganizationof competitionfrom visitingspecies? It is potentially of greatmagnitude (Ainley 1976).

I RESIDENTS FLEDGING YOUNG I•] VISITORS

J F M A M J J A S O N D

Figure10. Fledgingperiods in Californiabreeding seabirds compared to the abundanceof visitingspecies. Visitorswere tabulatedfor monthsin whichtheir relativeabundance exceeded 15 percentof the yeaflytotal (seeFigure 2). 63 SEABIRD OCCURRENCE

SUMMARY

The occurrenceand distributionof 28 marinebird speciesthat visit the coastalwaters of Californiawas describedfrom data providedin Audubon Field Notes/American Birds for the years 1955 to 1973. Where possible,yearly differencesin occurrencewere related to ocean temperatures,salinities and productivity. Best correlationswere de- rived from water temperatures,especially for such"southern" species as Black Storm-Petrel and Xantus' Murrelet. Marine bird communities north and south of Point Conception,an oceanographicboundary region, were compared,including breeding and visitingspecies, based on temperatureconditions of the two regions.The upwellingof cold water in areasoccurring the length of the state effected extensiveoverlap in breedingavifaunas and in visitingspecies during the upwellingperiod. During the oceanicand DavidsonCurrent periods(e.g. fall and winter) there was lessoverlap in visitingspecies of the two regions,although abnormallywarm conditionsin the fall and winter or abnormallycold conditionsin the winter causedgreater overlap. Peaknumbers and spe- ciesdiversity of visitingseabirds occurred during late summerand fall, a periodwhen food resourcesare supposedlycritical for residentspecies off California.

ACKNOWLEDGMENTS

This paper was made possibleby the conscientiousefforts of many observersand the work of regionaleditors for Audubon Field Notes/ American Birds. All of these personsare listed in the 1955 through 1973 issuesof that journal. Bill Tweit helpedme to extract data from thosereports. MargaretK. Robinsonand EdytheM. Drollingerprovid- ed me with ScrippsInstitution of OceanographyData Reports;the U.S. Coast Guard Radiation ThermometerProgram provided back and current issuesof their isotherm charts. Malvern Gilmartin, Hopkins Ma- rine Station, gave helpful counselon the oceanographyof the region and directedme initially toward sourcesof informationon the subject. The paperwas improved through the criticalcomments on initial manu- scripts given by Daniel W. Anderson,Alan Baldridge,Alan M. Craig, David Gaines,Joseph R. Jehl, R. Guy McCaskie,Gerald R. Sangerand Richard W. Stallcup. Alan Baldridge'sand Jerry Sanger'sknowledge on both the seabirdsand oceanographyof the easternNorth Pacificwas particularlyhelpful. This is Contribution 102 of Point ReyesBird Ob- servatory.

64 SEABIRD OCCURRENCE

LITERATURE CITED

Abbott, D. P. and R. Albee. 1967. Summary of thermal conditionsand phytoplankton volumesmeasured in Monterey Bay, California 1961-1966. Calif. Coop. Ocean. Fish. Invest. Rep. 11..155-156. Ainley, D. G. MS. Feedingmethods in seabirds:a comparisonof polar and tropical communities. In G. A. Llano, ed. Adaptationsin Antarctic ecosystems, Third Syrup.Antarctic Ecol., Washington,D.C.: in press. Ainley, D. G. and T. J. Lewis. 1974. The history of Farallon Island marinebird populations1854-1972. Condor 76:432-446. Ainley, D. G., T. J. Lewis and S. Morrell. 1976. Molt in Leach'sand Ashy Storm- Petrels. Wilson Bull. 87:76-95. Ainley, D. G., S. Morrell and T. J. Lewis. 1974. Patternsin the life historiesof storm-petrelson the Farallon Islands. Living Bird 13 .'295-312. Ainley, D. G. and T. Osborne. 1972. A Marin County, California,breeding site for Ashy Petrels. Calif. Birds 3 ..71. Ainley, D. G. and M. C. Whitt. 1973. Numbersof marinebirds breeding in northern California. West. Birds 4:65-70. AmericanOrnithologists' Union. 1957. Check-listof North Americanbirds. Fifth ed. Am. Ornithol. Union, Baltimore, Md. Anderson, D. W. and I. T. Anderson. 1976. Distribution and status of Brown Pelicans in the California Current. Am. Birds 30:3-12. Ashmole, N.P. 1971. Sea bird ecology and the marine environment. Pages 223-286 in D. S. Farner and J. R. King, eds.Avian biology,vol. 1. Academic Press, New York. Ashmole, N. P. and M. J. Ashmole. 1967. Comparativefeeding ecology of seabirds of a tropical oceanicisland. PeabodyMus. Nat. Hist., Yale Univ., Bull. 24:1-131. Bakun, A. 1973. Coastalupwelling indices,west coastof North America, 1946- 71. U.S. Dept. Comm., NOAA Tech. Rep. NMFS SSRF-671, Seattle. Beck, R. H. 1910. Water birds of the vicinity of Point Pitios, California. Proc. Calif. Acad. Sci., 4th Ser., 3:57-72. Bent, A. C. 1919. Life historiesof North American diving birds. U.S. Natl. Mus. Bull. 107.-132-140. Bent, A.C. 1921. Life historiesof North Americangulls and terns. U.S. Natl. Mus. Bull. 113. Bent, A. C. 1922. Life historiesof North American petrels and pelicansand their allies. U.S. Natl. Mus. Bull. 121..38-46. Bolin, R. L. and D. P. Abbott. 1963. Studies on the marine climate and phytoplankton of the central coastalarea of California, 1954-1960. Calif. Coop. Ocean. Fish. Invest. Rep. 9:23-45. Clapp, R. B. and P. W. Woodward. 1968. New recordsof birdsfrom the Hawaii- an Leeward Islands. Proc. U.S. Natl. Mus. 124(3640). Cody, M. L. 1973. Coexistence,coevolution and convergentevolution in seabird communities. Ecol. 54:31-44. Crossin,R.S. 1974. The storm petrels(Hydrobatidae). Pages165-176in W. B. King, ed. Pelagicstudies of seabirdsin the central and easternPacific Ocean. Smithsonian Contrib. Zool. 158. Devillers,P. 1972. The juvenal plumageof Kittlitz's Murrelet. Calif. Birds 3: 33-38. Dodimead, A. J., F. Favorite and T. Hirano. 1963. Review of oceanographyof the subarcticPacific region. Int. N. Pac. Fish. Comm. Bull. 13:1-195. Drent, R. H. and C. J. Guiguet. 1961. A catalogueof BritishColumbia sea-bird colonies. Brit. Col. Prov. Mus. Occ. PaperNo. 12. 65 SEABIRD OCCURRENCE

Fink, B. D. andW. H. Baylift. 1970. Migrationsof yellowfinand skipjack tuna in the easternPacific Ocean as determined by taggingexperiments, 1952-1964. Inter-Am. Trop. Tuna Comm. Bull. 15:1-227. Fisher,H. I. and J. R. Fisher. 1972. The oceanicdistribution of the LaysanAl- batross, Diornedea imrnutabilis. Wilson Bull. 84:7-27. Frey, H. W. 1971. California'sliving marine resourcesand their utilization. Calif. Dept. Fish and Game, Sacramento. Gress,F., R. W. Risebrough,D. W. Anderson,L. F. Kiff and J. R. Jehl, Jr. 1973. Reproductive failures of Double-crestedCormorants in southern California. Wilson Bull. 85:197-208. Hamilton,W. J., III. 1958. Pelagicbirds observed on a North Pacificcrossing. Condor 60:159-164. Holmes,R. T. 1964. Noteson occurrenceof the LaysanAlbatross near the Cali- fornia coast. Condor 66: 302-303. Hubbs,C. L. 1963. The marinevertebrates of the outer coast. Syst. Zool. 9:134-147. Hunt, G. L., Jr. and M. W. Hunt. 1974. Trophic levelsand turnover rates: the avifauna of Santa Barbara Island. Condor 76: 363-369. Idyll, C. P. 1973. The anchovycrisis. Sci.Am. 228(6):22-29. Jehl, J. R., Jr. 1974. The near-shore avifauna of the middle American west coast. Auk 91:681-699. Jordan, R. 1967. The predationof guanobirds on the PeruvianAnchovy (En- graulisringens Jenyns). Calif. Coop.Ocean. Fish. Invest. Rep. 11:105-109. Joseph,J. and R. P. Calkins. 1969. Populationdynamics of the skipjacktuna (Katsuwonuspelamis) of the easternPacific Ocean. Inter-Am. Trop. Tuna Comm. Bull. 13(1):7-273. King, W. B. 1970. The trade wind zone oceanographypilot study, part VII: seabirdobservations March 1964 to June 1965. U.S. Fish Wildl. Serv.Spec. Sci. Rep. Fish. 586. Kuroda, N. 1955. Observationsof pelagicbirds of the northwest Pacific. Con- dor 57:290-300. Lack, D. 1966. Populationstudies of birds. ClarendonPress, Oxford. Lack, D. 1968. Ecologicaladaptations for breeding in birds. Methuen and Co., London. Loomis, L.M. 1895. California water birds. No. I--Monterey and vicinity from the middle of June to the end of August. Proc. Calif. Acad. Sci., 2nd Ser., 5:177-224. Loomis, L. M. 1896. California water birds No. II-Vicinity of Monterey in mid- winter. Proc. Calif. Acad. Sci., 2nd Ser., 6:1-30. Loomis, L. M. 1918. A review of the albatrosses,petrels, and diving petrels. Proc. Calif. Acad. Sci., 4th Ser., 2:1-187. McCaskie, G. 1970. The occurrencesof four speciesof pelecaniformesin the southwestern United States. Calif. Birds 1:117-142. McHugh, J. L. 1950. Increasingabundance of albatrossesoff the coast of Cali- fornia. Condor 52:153-156. Marshall,A. J. and D. L. Serventy. 1956. The breedingcycle of the Short-tailed Shearwater,Puffinus tenuirostris(Temminck), in relation to trans-equatorial migration and its environment. Proc. Zool.'Soc. London 127(4):489-510. Martin, P. W. and M. T. Myres. 1969. Observationson the distributionand migration of some seabirdsoff the outer coastsof British Columbiaand Washing- ton state, 1946-49. Syesis2:241-256. Miller, L. 1940. Observations on the Black-footed Albatross. Condor 42:229- 238. Murphy, R. C. 1925. Bird islandsof Peru. G.P. Putnam and Sons, New York.

66 SEABIRD OCCURRENCE

Murphy, R. C. 1936. Oceanicbirds of South America. MacMillan, New York. Murphy, R. C. 1967. Distributionof North Atlantic pelagicbirds. Serialatlas of the marine environment,Folio 14. Am. Geogr.Soc., New York. Osborne,,T. and J. Reynolds. 1971. California seabirdbreeding ground survey. Wildl. Manage.Branch Admin. Rep. No. 71-3, Calif. Dept. Fish and Game, Sacramento. Palmer, R.S. 1962. Handbook of North American birds, vol. 1. Yale Univ. Press, New Haven. Pearson,T. H. 1968. The feeding biology of sea-birdspecies breeding on the Farne Islands, Northumberland. J. Anim. Ecol. 37:521-552. Phillips,J. H. 1963. The pelagicdistribution of the Sooty Shearwater,Procellaria grisea. Ibis 105:340-353. Reid, J. L., Jr., G.I. Rodenand J. G. Wyllie. 1958. Studiesof the CaliforniaCur- rent system. Calif. Coop. Ocean. Fish. Invest. Prog. Rep. ! July 1956-1 Janu- ary 1958. Rice, D. W. and K. W. Kenyon. 1962. Breedingcycles and behavior of Laysan and Black-footed albatrosses. Auk 79:517-567. Richardson,F. 1961. Breedingbiology of the RhinocerosAuklet on Protection Island,Washington. Condor 63:456-473. Richdale,L. E. 1957. Recoveryof a Sooty Shearwaterin northernhemisphere. Ibis. 99:116. Richdale, L. E. 1963. Biology of the Sooty ShearwaterPuffinus griseus. Proc. Zool. Soc. London 141:1-117. Robbins,C. S. and D. W. Rice. 1974. Recoveriesof banded LaysanAlbatrosses (Diomedea immutabilis) and Black-looted Albatrosses(D. nigripes). Pages 232-271 in W. B. King,ed. Pelagicstudies of seabirdsin the centraland eastern Pacific Ocean. Smithsonian Contrib. Zool. 158. Sanger,G.A. 1970. The seasonaldistribution of someseabirds off Washington and Oregonwith noteson their ecologyand behavior. Condor72:339-357. Sanger,G.A. 1972. Preliminarystanding stock and biomass estimates of seabirds in the subarcticPacific region. Pages589-611 in A. Y. Takenouti et al., eds. Biologicaloceanography of the northernNorth PacificOcean. IdemitsuSho- ten, Tokyo. Sanger,G.A. 1973. New northernrecord for Xantus'Murrelet. Condor75:253. Sanger,G.A. 1974a. Black-looted Albatross (Diomedea nigripes). Pages96- 128 in W. B. King, ed. Pelagicstudies of seabirdsin the central and eastern Pacific Ocean. Smithsonian Contrib. Zool. 158. Sanger,G.A. 1974b. LaysanAlbatross (Diomedea immutabilis). Pages129-153 in W. B. King, ed. Pelagicstudies of seabirdsin the centraland easternPacific Ocean. Smithsonian Contrib. Zool. 158. Schreiber,R. W. and R. W. Risebrough. 1972. Studiesof the Brown Pelican. Wilson Bull. 84:119-135. Scott, J. M. 1973. Resourceallocation in four syntopicspecies of marine diving birds. Ph.D. Thesis. Oregon State Univ., Corvallis. Scott, J. M., J. Butler, W. G. Pearcy and G. A. Bertrand. 1971. Occurrenceof the Xantus' Murrelet off the Oregoncoast. Condor 73:254. Scott, J. M., W. Hoffman, D. G. Ainley and C. F. Zeillemaker. 1974. Rangeex- pansionand activity patternsin RhinocerosAuklets. West.Birds 5:13-20. Scripps Institution of Oceanography. 1956-72. Data Reports: surface water temperaturesat shorestations. La Jolla. Sealy, S. G. 1974. Breedingphenology and clutch sizein the Marbled Murrelet. Auk 91:10-23. Serventy,D. L., V. Serventyand J. Warham. 1971. The handbookof Australian sea-birds. A. H. and A. W. Reed, Sydney.

67 SEABIRD OCCURRENCE

Sette,O. E. and J. D. Isaacs,eds. 1960. The changingPacific Ocean in 1957 and 1958. Calif. Coop. Ocean. Fish. Invest. Rep. 7:13-217. Shuntoy,V. P. 1972. Seabirds and the biologicalstructure of the ocean. (Transl. from Russian)Bur. Sport Fish.Wild. and Natl. Sci. Found.,Washington, D.C. Smail, J., D. G. Ainley and H. Strong. 1972. Notes on birds killed in the 1971 San Franciscooil spill. Calif. Birds 3:25-32. Smith, P. E. 1971. Distributionalatlas of zooplanktonvolumes in the California Current region, 1951 through 1966. Calif. Coop. Ocean. Fish. Invest. Atlas No. 13. Storer, R. W. 1952. A comparisonof variation, behavior, and evolution in the sea-birdgenera Uria and Ceppbus.Univ. Calif. Publ. Zool. 52:121-222. Thompson,D. Q. 1951. Noteson distributionof North Pacificalbatrosses. Auk 68:227-235. Warham,J. 1964. Marked Sooty ShearwatersPuffinus griseus in the northern hemisphere. Ibis 106: 390-391. Williams,F. 1972. Considerationof three proposedmodels of the migrationof young skipjack tuna (Katsu•vonuspelarnis) into the eastern Pacific Ocean. U.S. Natl. Mar. Fish. Serv., Fish. Bull. 70(3):741-762. Wynne-Edwards,V. C. 1951. On the habits and distribution of birds on the North Atlantic. Proc. Boston Soc. Nat. Hist. 40(4):233-346.