SCIENCE expansionof the Elegant Tern's breedingrange might be expected (Garrett and Dunn 1981:192). We report herethe establishmentof a ELEGANTTERNS breedingpopulation in Orange County,California, approximately 73 kilometersnorthwest of theonly BREEDINGINORANGE otherUnited States breeding colony locatedin SanDiego Bay. In the latespring and summer of •986, a flockof 200-250__Elegant COUNTY,CALIFORNIA •ernswas present atthe Bolsa Chica EcologicalReserve, Orange County. The 530-acre reserve is a saltmarsh environment managed by the CaliforniaDepartment of Fishand Game.During June the ternsoften spenttime on the groundin dense aggregationson both North and byCharles T. Collins, South Islands, two sand-fill islands thatwere created in 1978as nesting William A. Schew,and EstherBurkett sitesfor the endangeredCalifornia Least Tern (Sterna antillarum THEELEGANT TERN (STERNA ELEGANS) Pacific coast of Baja California browre).The two islandsare located occurscommonly to abundantlyon (Bancroft 1927), have not been in a part of the reservewhich has a the southern and central California activebreeding sites in recentyears mutedtidal regime. These aggrega- coast, particularly from July to (Wilbur 1987, Schaffner1986). tions closely resemblednesting October,when it rangesnorth as far assemblages,and ground courtship asMonterey Bay, San Francisco Bay, displayswere frequently observed and Point Reyes (Small 1974, throughoutthis period. Although Harrison 1983, A.O.U. 1983, the terns made numerous shallow Shufordet al. 1989). It alsooccurs, scrapesin thesand, we could find no lesscommonly, still farther north in eggsor other .evidenceof actual Oregon(Fix andHeinl 1990), and breeding.InlnI•8•, weobserved simi- rarelyin Washingtonand British lar aggregations,particularly on Columbia (Godfrey 1986). The North Island,and t•hi•y_-one p•trs ElegantTern's winter range extends laid eggsin a singlecluster on the southalong the Pacific coast as far as edgeof, and slightly intermixed with, Ecuador,Peru, and Chile (Harrison a groupof nestingCaspian Terns (S. 1983; A.O.U. 1983). Despite its caspia).Most of theseeggs were extensiverange there have been, in destroyedby two or three non- recentyears, only two known breed- breedingWestern Gulls (Larus occi- ing coloniesof thisspecies: a very dentalis)that frequentedNorth largecolony of about 10,000 pairs on Islandthat summerand preyed on IslaRaza, Gulf of California(Wilbur Caspianand Elegant tern eggs.At 1987, Walker 1965) and, since1959, Adult ElegantTern in breedingplumage with young.Bolsa Chica EcologicalReserve. leastone fledgling Elegant Tern was a smallerone of 600-860pairs on the raised that season. salt pond dikes of southernSan Over the pastdecade there has In 1988,the breeding population DiegoBay, California (Unitt 1984, been an increase in the number of of ElegantTerns increased to 450 Schaffner1985). Previouslyrecord- spring recordsof adults on the pairs,again nesting on NorthIsland ed colonies,particularly on Isla California coast, particularly in in hexagonallypacked aggregations, Cerralvo in the Gulf of California Orange,Los Angeles, Ventura, and typicalterns(Buckley of severaland species Buckley of"crested" 1977). (Banks1963) and at LagunaOjo de Santa Barbara counties in southern Liebreand Isla SanRoque on the California,suggesting that a further There were approximately1200

Volume 45, Number 3- $95 ingpopulations of BlackSkimmers California (Garrett and Dunn 1981, (Rynchopsniger) and Forster's Terns Shufordetal. 1989).Elegant Terns (S.forstert] as well asCaspian and nowregularly occur at othersites on Royalterns; the smaller Least Terns thesouthern California coast in April haverelocated their nesting activities eachyear, sometimes in groupsof to nearbySouth Island. With contin- severaldozen. Much courtship activ- ued successfulreproduction the ity andeven copulations have been Elegant Tern population could observed, but none remain to nest increasein comingyears. (K.L. Garrett,pers. comm.). Late The establishmentand growth of summerpeak abundances of typical- thebreeding colony of ElegantTerns ly 2000-3000, and rarely 6000 at BolsaChica is unquestionably ElegantTerns have been recorded in related to the dramatic increase in its the PointReyes area (Shuford eta/. overallrange, seasonal occurrence, 1989) and up to 400 - 450 birdsat and abundancealong the Pacific Humboldt Bay (Fix and Heinl coast,particularly since the 1970s. 1990). Theyhave occurred in small Prior to 1950, Elegant Terns numbersof upto a fewdozen in four Denselypacked nests, containing single occurredrarely and irregularly as far of the lastseven years in southern eggs,of ElegantTerns. BolsaChica northas San Francisco Bay (Grinnell EcologdcalReserve 1989. Oregon(Fix and Hein11990). There and Miller 1944). Within the last arefewer than 15 records of Elegant breedingpairs of Elegant .T,,.•ns on threedecades, their post-breeding Terns in Washington(Washington North Islandin .1989,and .1075in dispersalhas taken them north fre- Bird Records Committee 1989). 1990.In thelatter two years, the nests quentlyto the PointReyes area of Since1950, duringthe periodof were divided into three to five dusters MarinCounty (Shuford eta/. 1989), rapidincrease in ElegantTern num- of highly synchronizednests. In occasionallyto Humboldt Bay bersand range, Royal Tern popula- 1988-1990 there was substantial (Morlan and Erickson 1988), and tionshave decreased markedly and breedingsuccess with up to 850late- southernOregon (Fix and Heinl havewithdrawn almost entirely from stagechicks being banded in 1989, 1990).Major northward flights took centralCalifornia (Cogswell 1977; and 430 in 1990. Each chick was substantialnumbers of Elegant Terns Garrett and Dunn 1981). Roberson banded with a United States Fish and to Washington(Washington Bird (1985)cites only six records of Royal Wildlife Service numbered alu- Records Committee 1989) and Ternsduring the pasttwo decades minumband which was also wrapped BritishColumbia (Godfrey 1986) in fromMonterey County. with coloredtape. Substantial num- 1983, and to Washingtonin 1990 In bothcases the changes in the bersof fledglings were seen later in the (Tweit and Fix 1991). There hasalso populationstatus of thesetwo terns summerof eachyear, some of which beena markedincrease in latespring seemsdirectly related to changesin returned to breed. and early summer records in their fish food stocks. The Northern TheElegant Terns usually nested in dghtunispedfic groups but sometimes with a fewCaspian Terns along the outerperiphery. In 1988-1990,from two to ten pairsof RoyalTerns (S. maxima)were also present and nested withinthe clusters of ElegantTerns. The rapidincrease in sizeof the breedingpopulation of Elegant Ternsat BolsaChica closely resem- blesthe patternof colonygrowth thatoccurred in SanDiego Bay fol- lowing the first nestingin 1959 (Unitt1984). The Elegant Tern pop- ulation at Bolsa Chica seems to have stabilized,at leasttemporarily, at about1100 pairs.They nowshare NorthIsland with similarly expand- Nestingaggregation of Elegantand Caspian terns. Boise Chica Ecological Reserve 1990.

394 - AmericanBirds, Fall 1991 Anchovy(Engraulis mordax), a prin- madehelpful comments oft, an earlier. 1988.Supplement to theB•rds of cipalfood item of theElegant Tern, draftof this paper. Northern California in: hasgreatly increased in abundance McCaskie, G., DeBenedictis, P., andrange, particularly in northern Literature Cited EricksonR., andMorlan, J. 1979. Californiain thelate summer (Smith AMERICAN ORNITHOLOGISTS' Birds of Northern California: An andEpley 1982). The Pacific Sardine UNION. 1983. Check-list of annotated Field List. 2nd Edition. (Sardinopssagax), a principal food North American Birds, 6th ed. GoldenGate Audubon Society, itemof theRoyal Tern, has decreased AmericanOrnithologists' Union, Berkeley. to near-extinction levels since 1950 Washington,D.C. ROBERSON,D. 1985. Monterey (MacCall 1979, 1984). There is BANCROFT,G. 1927.Breeding Birds. Monterey Peninsula some indication of an increase in birds of ScammonsLagoon, AudubonSociety. 266 pgs. their numbersin recentyears. The Lower California. Condor 29: SCHAFFNER,F.C. 1985.RoyalTern probablycausal relationship between 29-57. V nestingattempts in California: thechange in rangeand abundance BANKS, R.C. 1963. Birds of isolatedor significantincidents? of thesetwo coastalforaging terns CerralvoIsland, Baja California. P(•sternBirds 15:71-80. andtheir principal fish prey items has Condor65:300-312. __! 986.Trends in ElegantTern and beenpreviously pointed out by BUCKLEY, P.A., and F.G. northernanchovy populations in Schaffner( 1985, 1986). Schaffner BUCKLEY. 1977. Hexagonal California. Condor88:347-354. (1985) also noted that the prior packingof RoyalTern nests. Auk SHUFORD, W.D., G.W. PAGE, establishmentof nesting colonies of 94:36-43. J.G. EVENSand L.E. STENZEL. themore aggressive, predator mob- COGSWELL, H.L. 1977. 1989. Seasonal abundance of bing, CaspianTerns, with which Waterbirds of California. Univ. waterbirdsat PointReyes; acoastal theseterns appear to selectivelynest, California,Los Angeles. Californiaperspective. Western mayhave been a precondition for the FIX, D. andS. HEINL. 1990. Birds20:137-265. establishmentof newElegant and Fieldnotes:western Oregon, fall SMALL, A. 1974. The Birds of Royaltern colonies in coastalsouth- 1989.Oregon Birds 15: 180-198. California.Winchester Press, 'New ern California.It is probablynot GARRETT, K. and J. DUNN. York. coincidental that the establishment 1981. Birds of Southern SMITH, P.E. and R.W. EPLEY. of a nestingcolony of ElegantTerns California.Los Angeles Audubon 1982.Primary production and the at Bolsa Chica coincided with that of Society,Los Angeles. anchovypopulation in thesouth- CaspianTerns which first bred at GODFREY, E. 1986. The Birds of ernCalifornia bight: comparison Bolsa Chica in 1986. Canada. (Revised Edition). andtime series. Limnol. Oceanogr. Numerousdeserted Elegant Tern National Museums of Canada, 27:1-17. eggsfrom the BolsaChica colony Toronto.595 pgs. TWEIT, B. and D. FIx. 1991. have been depositedwith the GRINNELL, J. andA.H. MILLER. Oregon/WashingtonRegion. Am. Western Foundation of Vertebrate 1944. The distribution of birds of Birds45:311. Zoology.Specimens of adultsand California.Pac. Coast Avifauna UNITT, P. 1984. The Birds of San chicks which were found dead are 27: 1-608. Diego County.San Diego Soc. housedin theornithological collec- HARRISON, P. 1983. Seabirds,An Nat. Hist. Memoir 13. tionsof CaliforniaState University, IdentificationGuide. Houghton WALKER,W.L. 1965.Baja's island LongBeach. Photographic docu- Mifflin Co., Boston. ofbirds. Pac. Discovery 18: 42-47. mentationof thebreeding aggrega- MACCALL,A.D. 1979.Population WASHINGTON BIRD RECORDS tions and nestshas been contributed estimatesfor thewaning years of COMMITTEE. 1989. Checklist of to VIREO. thePacific Sardine fishery. Calif. WashingtonBirds. Washington Coop.Fish. Invest. Rept. 20:72-82. Birds l : l- 5 . Acknowledgments __1984. Seabird-fisherytrophic WILBUR,S.R. 1987.Birds of Baja Weare indebted to themany people interactions in the eastern Pacific California. Univ. Calif. Press, whohave braved attacks by belligerent boundarycurrents: California and Berkeley. CaspianTerns to assist us with the nest Peru. Pp. 131-148 in: D.N. countand chick banding programs at Nettleship,G.A. Sangerand P.E Bolsa Chica. K.L. Garrett called our Springer, eds. Eighth Ann. •Department of Biology,Californ& State attentionto severalreferences dealing MeetingPacific Seabird Group. Universit3 Long Beach, CA 90840 (Collins and Schew)and Calia•brnia Department ofFish and withthe status of ElegantTerns else- Spec.Publ. Canadian Wildlij• Serv. Game,11862 MacGill, Garden Grove, CA92641 where on the California coast and MORLAN, J. and R. ERICKSON. (Burkett)

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