NOTES

WHERE DO PIGEON GUliI_FMOTS FROM GO FOR THE WINTER?

TERENCER. WAHL, 3041 Eldridge,Bellingham, 98225 BILL TWEIT, P.O. Box 1271, Olympia,Washington 98507

The PigeonGuillemot ( columba) nests at numeroussmall colonies and scatteredindividual sites from the Channel Islands,California, north to (Ewins et al. 1993). Duringthe nonbreedingseason are virtually absent from California, ,and the outercoast of Washington(e.g., Briggs et al. 1987), andthe winter distributionof PigeonGuillemots breeding along the westcoast of NorthAmerica is at bestincompletely known. The species'postbreeding movements have been thought to be to the northfrom Californiaand Oregon,though systematically collected data are minimal.There is evidencethat at leastsome move north to relativelyprotected watersof the Straitof Juande Fuca,, and adjacent areas ("inland marine waters")of Washingtonand BritishColumbia (e.g., Ainley et al. 1990, Ewins1993, Ewinset al. 1993), wheresome census records indicate that numbers increase during thewinter (e.g., Campbell et al. 1990). Herewe contributeto theunderstanding ofthe winteringareas of PigeonGuillemots along the Pacificcoast by summarizingrecords from one-dayboat trips off southwesternWashington over 28 years. BetweenSeptember 1971 and October1999 we systematicallycensused during316 one-daybird-watching cruises aboard chartered sportfishing vessels off GraysHarbor, Washington (see Wahl and Tweit 2000). Effortwas greatest in January and from April throughmid-October (Table 1). Numbersof birdswere countedor estimatedfor censusperiods of about30 minutes(within "depth habitats"; Table 2). A total of 6306 individualcensus periods covered 43,758 km. Guillemotswere recordedonly from Marchinto October,and our analysisis for thosemonths only (Tables2 and 3). In additionto these cruises,Wahl spent four weeks total in September,January, and April on a Universityof Washingtonresearch vessel off CopalisBeach, Washington, about 20 km northof GraysHarbor, censusing birds and mammalsto 126 ø 30'W (data not usedin Tables 1-3). Though censuseffort was much greater offshore,almost 90% of recordedwere in the GraysHarbor entrance channel and immediately offshore within

Table ! PigeonGuillemot Censuses from Grays Harbor out to 2000-m Depth, September1971-October 1999

Month Total birds Censuseffort (kin) Birds/krn

Jan 0 1,232 0 Feb 0 262 0 Mar 62 461 0.13 Apr 173 2,481 0.07 May 809 4,783 0.17 Jun 252 869 0.29 Jul 749 5,798 0.13 Aug 1507 11,262 0.13 Sep 136 11,592 0.01 Oct 40 4697 0.01 Nov 0 197 0 Dec 0 124 0

Western Birds 31:203-206, 2000 203 NOTES

'Fal•le 2 PigeonGuillemot Numbers by Depth, March-October

Depth Totalbirds Censuseffort (km) Birds/km

GraysHarbor channel 2909 2938 0.99 <20 m 400 3,016 0.13 20-50 m 227 4,253 0.05 50-100 m 67 9,261 0.01 100-200 m 75 13,684 0.01 200-1000 m 45 7,360 0.01 1000-2000 m 5 867 0.01 >2000 m 0 565 0.00 Total 3728 41,944 0.09

the 20-m-depthcontour, and another6% were justoutside of that (Table2). Highest numbers--fromMay to July(Table 3)--reflected at leastin part the nestingactivity of some 10-20 pairs(Speich and Wahl 1989, unpubl.obs.). In August,and to a lesser extent in September,we noted adults in postbreedingplumage, usuallyin small groups,flying north, with a few birdsrecorded to the edgeof the continentalshelf over depthsof 1000 to 2000 m (Table3), as far west as 125 ø 07' W. These birdswere flyinga routethat wouldbe essentiallya straightline from northernCalifornia and Oregon to the entranceto the Strait of Juan de Fuca. In September,birds per kilometerdropped by over90% from May-Augustnumbers, with onlya few notedfar offshore.On surveysadditional to the trips summarizedhere, two guillemotswere seen30-40 km offshore,one eachin September1968 and 1976 (Wahlunpubl.). By Octoberno birdswere seenoffshore. None at all were seenon November-February trips (Table 1), on researchcruises west to 126 ø 30'W, or on two late January-early Februarytrips south along 125ø W off Washingtonand Oregon (Wahl unpubl.), stronglysuggesting that Pigeon Guillemotsdo not winter offshore.Our spring (March-May)survey sample size is small,but the eightbirds seen offshore then may indicate a southbound offshore movement.

'Fal•le 3 PigeonGuillemots per Kilometeroff GraysHarbor by Ocean Depth and Month, 1971-1999

Mar Apr May Jun Jul Aug Sep Oct

GraysHarbor channel 1.41 1.31 1.53 2.23 1.51 0.12 0.11 <20 m -- 0.15 0.39 0.01 0.16 0.17 0.02 0.02 20-50 m 0.02 -- 0.14 0.94 +a 0.02 0.01 0.00 50--100 m -- + + -- + 0.02 0.01 -- 100-200 m 0.01 + + -- -- 0.02 + -- 200-1000 m ------0.01 -- 0.02 + -- 1000-2000 m ncb -- -- nc -- 0.02 -- -- >2000 m nc -- -- nc nc nc -- -- All depths 0.13 0.07 0.17 0.29 0.13 0.13 0.01 0.01 apresent,<0.01. bnc,no census.

204 NOTES

Briggset al. (1987) statedthat guillemots"almost leave" California from August throughFebruary. Ainley et al. (1990) reporteda northwardseasonal shift of recoveriesof fledglingsbanded on the FarallonIslands to at leastas far as British Columbiaand that afterOctober one-third of recoverieswere fromWashington north. Christmasbird count(CBC) data indicatesmall numbers of birdsalong the Oregon coastin winter.In BritishColumbia, Vermeer and Morgan(1997) statedthat few guillemotsremain in the QueenCharlotte Islands after early September. Campbell et al. (1990) describedmovement of birdsfrom the BritishColumbia coast into Queen CharlotteSound and protected waters of the straitsof Georgiaand Juan de Fuca;thus it islikely that birds breeding north of Washingtonalso winter in inlandmarine waters. Systematic,year-round census data coveringall of Washington'sinland marine watersare lacking,though there have been a numberof surveyscovering parts of the region.Comparisons between seasons are complicatedby varyingcensus methods, seasonalvariations in observationconditions, and differencesin the detectabilityand identificationof PigeonGuillemots. Dispersing and foragingbirds from a few large coloniesfurther complicate analysis of existingdata. Numbers from CBCsin Washing- ton suggestthat guillemotsshift into inlandmarine waters in winter.At GraysHarbor guillemotswere found on 11 of 24 CBCsfrom 1972 to 1997, witha maximumof five birds. In contrast,counts in inland marine waters were relativelyhigh, (e.g., a maximumof 1221 on 22 December1989 at Sequim-Dungeness).Other surveysin the San Juan Islands,Georgia Strait, and PugetSound south to Olympiaproduced winternumbers far abovesummer breeding numbers. One consistenteffort in 1978- 79 (Wahlet al. 1981), in whichbirds were censusedmonthly from a ferrythrough the San JuanIslands, showed that November-Marchnumbers of PigeonGuillemots were aboutfive timesthose in Juneand July(Wahl unpubl.). Comparison of 14 CBCs in inlandmarine waters with data from othercensuses covering the sameareas (Wahl et al. 1981; unpubl.) suggestwinter numbersmay be twice as large as summer populationsand are too largeto consistof summerresidents only. Data from our surveysoff Grays Harbor supportthe conceptof a postbreeding migrationof PigeonGuillemots north from California, Oregon, and the outercoast of Washingtonto inlandmarine waters. Such a seasonalnorthward migration for the winter correspondswith that of many Brandt's Cormorants (?halacrocorax penicillatus;Boekelheide et al. 1990) andCommon Murres ( aalge;Briggs et al. 1992) and with patternsof postbreedingdispersal of Brown Pelicans(Pelecanus occidentalis)and Heermann'sGulls (Larus heermanni; Boekelheideet al. 1990). Guillemots'occurring generally near shoremakes them vulnerableto oil spills (Ewinset al. 1993). From our data, it appearsthat a largeproportion of the southern populationof PigeonGuillemots concentrates in a relativelylimited area of Washing- ton and BritishColumbia in winter.This area alsosupports heavy ship traffic, four oil refineries,and many other industries.A major winter oil spill here could pose a significantrisk to the entiresouthern population. For thisrisk to be assessed,detailed informationon the size,distribution, and geographic origins of the winteringpopula- tion in the watersof Washingtonand BritishColumbia is needed. Thanksare dueD. R. Paulson,B. LaBar,P. Anderson,a numberof otherassisting observers,and, especially,participants who financedtrips. D. G. Ainley and J. Hoddermade very helpful comments for correctionsof a sloppymanuscript.

LITERATURE CITED

Ainley, D. G., Boekelheide,R. J., Morrell, S. H., and Strong, C. S. 1990. Pigeon ,in Seabirdsof the FarallonIslands (D. G. Ainleyand R. J. Boekelheide, eds.),pp. 276-305. StanfordUniv. Press.Stanford, CA. Boekelheide,R. J., Ainley, D. G., Morrell, S. H., and Lewis, T. J. 1990. Brandt's Cormorant, in Seabirdsof the (D. G. Ainley and R. J. Boekelheide,eds.), pp. 163-194. StanfordUniv. Press.Stanford, CA.

2O5 NOTES

Briggs,K. T., Tyler,W. B., Lewis,D. B., and Carlson,D. R. 1987. communities at sea off California: 1975-1983. Studies Avian Biol. 11. Briggs,K. T., Varoujean,D. H., Williams,W. W., Ford, R. G., Bonnell,M. L., and Casey,J. L. 1992. Seabirdsof the Oregonand WashingtonOCS, 1989-1990, in Oregonand Washington marine mammal and seabirdsurveys. Final report (J. J. Brueggeman,ed.), pp. 3-1-3-156. OCS StudyMMS 91-0093. U.S. Dept. Interior,Minerals Mgmt. Service,Pacific OCS Office, 1340 W. Sixth St., Los Angeles,CA 90017. Campbell,R. W., Dawe, N. K., McTaggert-Cowan,I., Cooper, J. M., Kaiser,G. W., and McNall, M. C. E. 1990. The Birdsof BritishColumbia, vol. 2. Royal Br. Columbia Mus., Victoria. Ewins,P. J. 1993. Pigeon Guillemot(Ceppt•us coluraba), in the Birdsof (A. Poole and F. Gill, eds.),no. 49. Acad. Nat. Sci., Philadelphia. Ewins, P. J., Carter, H. R., and Shibaev,Y. V. 1993. The status,distribution, and ecologyof inshorefish-feeding alcids (Ceppt•us guillemots and Bract•yrarnpt•us murrelets)in the North Pacific,in The status,ecology and conservation of marine birdsof the North Pacific(K. Vermeer,K. T. Briggs,K. H. Morgan,and D. Siegel- Causey,eds.), pp. 164-175. Can. WildlifeServ. Spec. Publ., Ottawa. Morgan,K. H. 1997. The distributionand seasonalityof marinebirds of the Queen Charlotte Islands,in The ecology,status and conservationof marine and shorelinebirds of the Queen CharlotteIslands (K. Vermeer and K. H. Morgan, eds.),pp. 78-91. Can. WildlifeServ. Occas.Paper 93. Speich,S. M., andWahl, T. R. 1989. Catalogof Washingtonseabird colonies. U.S. Fish& WildlifeServ. Biol. Rep. 88 (6). MMS 89-0054. Wahl, T. R., Speich,S. M., Manuwal,D. A., Hirsch,K. V., and Miller, C. 1981. Marine bird populationsof the Strait of Juan de Fuca, Strait of Georgia and adjacentwaters in 1978 and 1979. U.S. EnvironmentalProtection Agency, DOC/EPA InteragencyEnergy/Environment Res. & Dev. ProgramRep. EPA/ 600/f-81/156. Natl. Oceanic& AtmosphericAdmin., 7600 Sand Point Way NE, Seattle, WA 98115. Wahl, T. R., and Speich,S. M. 1984. Surveyof marinebirds in PugetSound, Hood Canaland waters east of WhidbeyIsland, Washington, in summer1982. W. Birds 15:1-14. Wahl,T. R. andB. Tweit. 2000. Seabirdabundances off Washington,1972-1998. W. Birds 31:69-88.

Accepted 9 May 2000

206