Palacios, E. and L. Alfaro. 1992. First breeding coastal California environments. Colon. record of the Caspian Tern in Baja Waterbirds 17: 153-159. California (Norte), Mexico. West. Birds Small, A. 1994. California birds: Their status and 23:143-144. distribution. Ibis Publ. Co., Vista, CA. Roby, D. D., D. P. Craig, K. Collins, and S. L. Suryan, R. M., D. P. Craig, D. D. Roby, N. D. Alamany. 1998. Avian predation on Chelgren, K. Collis, W. D. Shuford and D. juvenile salmonids in the lower Columbia E. Lyons. 2004. Redistribution and growth River. 1997. Annual report submitted to of the Caspian Tern population in the the Bonneville Power Administration and Pacific Coast region of North America, U. S. Army Corps of Engineers. 1981-2000. Condor 106:777-790. Russell, S. M. and G. Monson. 1998. The birds Unit!, P. 1984. The birds of San Diego County. of Sonora. University of Arizona Press, San Diego Soc. Nat. Hist. Mem. 13: 1- Tucson, AZ. 276. Schew, W. A., C. T. Collins and T. E. Harvey. Wires, L. R. and F. J. Cuthbert. 2000. Trends in 1994. Growth and breeding biology of Caspian Tern numbers and distribution Caspian Terns (Sterna caspia) in two in North America: a review. Waterbirds 23:388-404,
Banding Studies of Elegant Terns in Southern California
Charles T. Collins Department of Biological Sciences California State University Long Beach, CA 90840 [email protected] In El Nino (warm water) years, post-breeding ABSTRACT movements extend northward to Washington and British Columbia, Canada (Campbell et al. 1990, Elegant Terns (Sterna e/egans) breed in three Burness et al. 1999). Breeding sites are limited to colonies in coastal southern California. In winter, three colonies in the United States, all in southern banded terns have been recovered from Mexico to California, and two to three sites in Mexico, with Chile, but mostly in coastal Central America. There the largest colony being located on Isla Rasa in is some fidelity to nesting areas and exchange the Gulf of California (Burness et al. 1999). among the California colonies. Thus far, there is Movements and colony locations of Elegant Terns no evidence of exchange with colonies in Mexico. are strongly related to the availability of their principal diet, schooling fish species, especially the INTRODUCTION northern anchovy ( Engraulis mordax) (Schaffner 1986, Horn et al. 1996), in California. In summer, Elegant Terns ( Sterna elegans) are commonly encountered on the Pacific coast of In southern California, Elegant Terns were first North America from Baja California, Mexico, to found breeding in south San Diego Bay in 1959 northern California and southern Oregon {Shuford (Gallop and Bailey 1960, Schaffner, 1986, Unitt et al. 1989, A.O.U. 1998, Small 1994, Burness et 1984). In 1987, a second colony was established al. 1999). at the Balsa Chica Ecological Reserve in Orange
Page 17 North American Bird Bander Vol. 31 No. 1 County (Collins el al. 1991 ); and in 1998, they to read bands (size 3) on Elegant Terns on these colonized a site at Los Angeles Harbor (K. Keane, occasions. This is unlike the similar studies of pers. com.) In recent years the breeding population Caspian Terns (Collins 2006) and Royal Terns of Elegant Terns in southern California has in (Collins and Doherty 2006) where substantial creased and the bulk of the nesting has shifted information was obtained from band (sizes 4 and among these three colony sites from year to year 5) read with a telescope both in and away from the (Collins, unpub.). A banding study was initiated at breeding colonies. Nearly all of the re-encounter Bolsa Chica in 1989 with additional banding done data presented here are from reports of Elegant in San Diego and at the Port of Los Angeles. The Terns submitted to the USGS Bird Banding outcome of this banding and subsequent re Laboratory (BBL). A few individuals were captured encounters is summarized here. alive in the breeding colonies entangled in monofilament fishing line and were cut loose and STUDY SITES released.
The principal study area has been the Bolsa Chica METHODS Ecological Reserve (Bolsa Chica, herein) in northern Orange County (Figure 1). Elegant Terns Between 1987 and 2005, a total of 16,564 pre-flying first bred here in 1987 (Collins et al. 1991) on one Elegant Tern chicks (HY/L) were banded with of two 1.7 ha (4 ac) sand islands established in standard, size 3, numbered aluminum bands issued 1978 as a nesting place for the endangered by the BBL. Most of the banding was done at Bolsa California Least Tern (Sterna antillarum brown,). Chica; chicks were also banded at the Salt Works This site has also been utilized by other species in one year, 1987, and at Pier 400 in four years beginning with Caspian Terns ( Sterna caspia) in between 1998 and 2003. Elegant Tern chicks 1986 (Cuthbert and Wires 1999, Collins 2006) congregate in a large creche within a few days after followed by Royal Terns (Sterna maxima), Forster's hatching (Burness et al. 1999). Banding of large Terns (Sterna forsteri) and Black Skimmers numbers of chicks was accomplished by herding (Rynchops niger). Throughout July and August the creche into a temporary 1 m high wire fence 2005, up to 1,000 Elegant Terns frequented the corral where they could be captured quickly, banded colony site used by Black Skimmers and Forster's and released by a team of "grabbers," "holders" Terns in the Upper Newport Bay Ecological Reserve and banders. In this manner, up to as many as (Figure 1). This may be a prelude to their colonizing this site in the near future. 3000 chicks were caught, banded and released in less than two hours. The creche quickly reformed In San Diego County, about 148 km south of Bolsa and no apparent impacts, other than the temporary Chica, Elegant Terns have nested on the dikes of disruption during banding operations, were noted. the salt evaporation ponds located in southern San RESULTS Diego Bay (Salt Works, herein). These ponds and dikes are now part of the South San Diego Bay A total of 84 Elegant Terns were re-encountered Unit of the San Diego National Wildlife Refuge. from one to nearly 12 years after initial banding. Since 1998, Elegant Terns have nested in associ Of these, 40 were reported as found dead, 26 were ation with California Least Terns and Caspian Terns reported to the BBL as found tangled in fishing line, at a newly established sand-fill area of the Port of and ten were reported as injured or caught by hand. Los Angeles (Pier 400, herein), 18 km west of Bolsa These categories may not be mutually exclusive, Chica in Los Angeles County (Figure 1). The initial 40 ha (100-ac) dredge fill area is now nearly as some birds found dead tangled in fishing line completely developed. The nesting terns are were simply reported as "found dead" and birds restricted to part of a 6 ha (15-ac) site set aside reported as injured or caught by hand also may for them immediately adjacent to what is currently have been partially tangled in fishing line. Two one of the busiest container cargo terminals on the individuals were reported as having been shot (in west coast. coastal western Mexico). Two additional birds were reported to the BBL by rehabilitation centers (it was Although they are encountered frequently, often in not known ii they survived and were released) and noisy roosting groups, little attempt has been made
Jan. - Mar. 2006 North American Bird Bander Page 18 WSANGELESCOUNTY / ' \ Bolsa Chica / \ Ecological Reserve \ / RIVERSIDE COUNTY ORANGE COUNTY I ··-. ·,. ,,=-~ Upper Newport Bay \ Ecological Reserve / / / ( ..r ..- .._ ..t _,-.. / ...... I ··-··-..- .. -.
SAN DIEGO COUNTY
San
South Bay Salt Works +J
Figure 1. Location of the three current breeding colonies of Elegant Terns in southern California. A possible future colony site (Upper Newport Bay Ecological Reserve) is also indicated.
Page 19 North American Bird Bander Vol. 31 No. 1 Table 1. lntercolony movements of Elegant Terns None of the 823 Elegant Terns banded at the Salt among southern California colonies Works between 1980 and 1982 (BBL) was encountered in this study. Similarly, no Elegant Banding Recovery S~e S~e Terns banded at any of the colonies in Mexico were Salt Works Bolsa Chica Pier 400 recovered in southern California. Conversely, no Salt Works 0 0 0 Elegant Terns banded in this study have been recovered, to date, in any of the Mexican colonies. Bolsa Chica 13 27 9 Pier 400 0 2 0 DISCUSSION four were caught in the breeding colonies, during this study, tangled in fish line and released Elegant Terns showed moderate fidelity to their unharmed. Sixty-three of the terns recovered (75%) natal colonies as indicated by the number of were re-encountered in southern California individuals banded at Balsa Chica and recovered between late March and early September, of which there in subsequent breeding seasons. However, 49 (58%) were in breeding colonies. Only 25% of when large-scale movements of the breeding the terns were encountered outside southern population were made among the three southern California in the non-breeding or migration periods California colonies, this appeared to override colony at locations ranging from coastal western Mexico fidelity. Many banded birds, most of which were to northern Chile. Although the bands on some of presumably banded at Balsa Chica, were observed the older terns are noticeably worn (pers. obs.), regularly in the nesting aggregations at Pier 400 they had not reached the point where band loss and the Salt Works in various years. was likely to have been significant. The lack of recoveries in southern California of any A total of 27 individuals banded at Balsa Chica were Elegant Terns banded in any of the Mexican also recovered there in subsequent breeding colonies and vice versa suggests that the three seasons. However, individuals banded at Balsa southern California breeding colonies form a Chica were also encountered at the Salt Works distinct metapopulation. Accordingly, the recent and at Pier 400 (Table 1). Two terns banded at population growth of Elegant Terns in southern Pier 400 were recovered at Balsa Chica. Since California seems to be the result of local breeding few Elegant Terns have been banded at the Salt success and recruitment of young into the breeding Works in recent years (none since 1987), ii is not population. The breeding population of Elegant surprising that none was recovered at the northern Terns in the three southern California colonies has colonies later in this study period. The actual increased from a few hundred pairs prior to 1986 number of individuals making inter-colony to over 5800 pairs in 1995 and 9300 pairs in 2005 movements is perhaps misleading. Most of the (Collins, unpub.). current banding was done at Balsa Chica, which would in large part account for the low re-encounter Elegant Terns are largely absent from California in of birds from the Salt Works and Pier 400. Also, winter with only a few stragglers being reported in the bulk of the southern California breeding December and January (Garrett and Dunn 1981 ). population of Elegant Terns has shifted among the Their r:iumbers decrease from September to early three colony sites from year to year. One such shift, November (Small 1994) when they depart on frorn Pier 400 to Balsa Chica in 2005, was related migration to Central and South American wintering to a single early season nocturnal predation event areas. Their winter range extends from coastal (presum-ably by an owl). In this case, 2300 nests Nayarit, Mexico, south to central Chile (Howell and with eggs were abandoned. Other shifts, including Webb 1995, AOU 1998, Burness et al. 1999). one from the northern colonies to the Salt Works Twenty-one of the banded Elegant Terns in this in 2003, may have been related to localized study were recovered from Sinaloa, Mexico (4) to changes in water temperatures and prey availability. Taital, Chile (1) including Guatemala (2), El Such shifts in the breeding population clearly Salvador (7) Nicaragua (1 ), Costa Rica (2), at sea influenced the number and location of band returns off Panama (1 ), and Colombia (3). Two individuals in those years. recovered in western Mexico in July were yearlings, Jan. - Mar. 2006 North American Bird Bander Page 20
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LITERATURE LITERATURE
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Chica Chica 21 21
Mexico, Mexico,
study study
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least least
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has has conduct conduct
approved approved master master
In In
ACKNOWLEDGMENTS ACKNOWLEDGMENTS
remain remain
future future
is is
area area
effects effects The coastal coastal
entrance entrance restoration restoration
Bolsa Bolsa
1992 1992
Terns Terns
collected collected
Colombia, Colombia,
Pacific Pacific individuals individuals
Malpelo Malpelo
Guatemala Guatemala
indicated indicated
distribution distribution
in in
and and
It It
Terns Terns
(Burness (Burness
population, population,
Rasa, Rasa,
be be
coastal coastal
America: America:
recoveries recoveries at at
Terns Terns
January), January), in in
California California obs.). obs.).
other other Burness Burness
characteristics) characteristics)
(Stiles (Stiles
pre-breeders pre-breeders which which Garrett, K. and J. Dunn. 1981. Birds of southern Schaffner, F. C. 1986. Trends in Elegant Tem California: Status and distribution. Los and northern anchovy populations in Angeles Audubon Society, Los Angeles, California. Condor 88:347-354. CA. Shuford, W. D., G. W. Page, J. G. Evens and L. Horn, M. H., P.A. Cole, and W. E. Loeffler. 1996. E. Stenzel. 1989. Seasonal abundance Prey resource base of the tern and skim of waterbirds at Point Reyes: a coastal mer colonies at the Balsa Chica Ecologi California perspective. West. Birds cal Reserve, Orange County, and The 20:137-265. Western Saltworks, south San Diego Bay. Small, A. 1994. California birds: their status and Final Report to U.S. Department of the distribution. Ibis Publ. Co., Vista, CA. Interior, Fish and Wildlife Service, Stiles, F. G. and A. F. Skutch. 1989. A guide to Contract No. 14-16-001-95586, Carlsbad, the birds of Costa Rica. Cornell University CA. Press, Ithaca, NY. Howell, S. N. G. and S. Webb. 1995. A guide to Unitt, P. 1984. The Birds of San Diego County. the birds of Mexico and northern Central San Diego Soc. Nat. Hist. Mem.13:1-276. America. Oxford University Press, New Velarde, E., J-L. E. Carton, H. Drummond, D.W. York, NY. Anderson, E. Palacios, and C. Rodriguez. Naranjo, L. G. and R. Franke. 1997. Confirma 2005. Nesting seabirds of the Gulf of cion de la presencia del gaviotin Sterna California's offshore islands: diversity, e/egans (Aves:Laridae) en Colombia. ecology, and conservation. Pp. 452-470 Boletin lnstituto de lnvestigaciones Mari in Biodiversity, ecosystems and conserva nas y Costeras 26: 109-112. tion in northern Mexico. (J-L. Cartron, G. Ridgely, R. S. and J. A. Gwynne. 1989. A guide Cepallos and R.S. Felger, eds.) Oxford to the birds of Panama, with Costa Rica, Univ. Press, NY. Nicaragua, and Honduras. 2nd Ed. Princeton University Press, Princeton, NJ.
Elegant Tern by George West
Jan. - Mar. 2006 North American Bird Bander Page 22