Shorebirds in Marine Environments FRANK A. PITELKA EDITOR MUSEUM OF VERTEBRATE ZOOLOGY UNIVERSITY OF CALIFORNlA BERKELEY CALIFORNIA 94720 Studies in Avian Biology No. 2 A PLJEKICATION OF THE COOPER ORNlTJ3OLOGICAL SOCIETY Cover Photographs: front, Sanderlings (Calidris alba); rear, Western Sandpipers (Calidris mawi); both taken on wintering grounds in central coastal California by Kenneth W. Gardiner. STUDIES IN AVIAN BIOLOGY Edited by RALPH J. RAITT with assistanceof JEAN P. THOMPSON at the Department of Biology New Mexico State University Las Cruces, New Mexico 88003 Studies in Avian Biology, as successorto Pacific Coast Avifauna, is a series of works too long for The Condor, published at irregular intervals by the Cooper Ornithological Society. Manuscripts for consideration should be sub- mitted to the Editor at the above address. Style and format should follow those of this and the previous issue or of The Condor. Price: $8.00 plus $0.90 for postage and handling ($0.50 plus 5% of price); for sales in California, add 6% of price for sales tax ($0.48). All orders cash in ad- vance; make checks payable to Cooper Ornithological Society. Send orders to Cooper Ornithological Society, c/o Department of Biology, University of Cali- fornia, Los Angeles, CA 90024. For information on other publications of the Society, see recent issues of The Condor. Printed by the Allen Press, Inc., Lawrence, Kansas 66044 13 June 1979 ii CONTENTS Preface . v Acknowledgments . vii Introduction: The Pacific Coast Shorebird Scene . 1 By Frank A. Pitelka Part 1: Distribution, Migration, and Conservation . 13 Aspects of the Occurrence of Shorebirds on a Central California Estuary........................................................... 15 By Gary W. Page, Lynne E. Stenzel, and Claire M. Wolfe Habitat Utilization by Wintering and Migrating Shorebirds on Humboldt Bay,California . 33 By R. H. Gerstenberg Banding Studies of Migrant Shorebirds in Northwestern Costa Rica . 41 By Susan M. Smith and F. Gary Stiles Notes on Charadriiformes of the South Coast of Peru . 49 By R. A. Hughes The Autumnal Migration of Baird’s Sandpiper . 55 By Joseph R. Jehl, Jr. Movements and Habitat Use by Wintering Populations of Willets and Marbled Godwits . 69 By Paul R. Kelly and Howard L. Cogswell Semipalmated Sandpiper Migration in North America . 83 By B. A. Harrington and R. I. G. Morrison Seasonal Habitat Use by Arctic Alaskan Shorebirds . 100 By P. G. Connors, J. P. Myers, and F. A. Pitelka A Preliminary Assessmentof Timing and Migration of Shorebirds Along the North Central Alaska Peninsula . 113 By Robert Gill, Jr. and Paul D. Jorgensen Migratory Shorebird Populations on the Copper River Delta and Eastern Prince William Sound, Alaska . 125 By M. E. “Pete” Isleib An Evaluation of the Copper River Delta as a Critical Habitat for Migrating Shorebirds . 131 By Stanley E. Senner Results of the California Shorebird Survey . 147 By Ronald M. Jurek Conservation and Management of Coastal Wetlands in California . 151 By John Speth Shorebird Census Studies in Britain . 157 By A. J. Prater Effect of Habitat Loss on the Numbers of Overwintering Shorebirds . 167 By J. D. Goss-Custard Summarizing Remarks, Part 1 . 179 By Joseph R. Jehl, Jr. 111 Part2: Ecology . 183 Feeding Ecology of Black Oystercatchers on South Farallon Island, California (abstract only) . 185 By Stephen H. Morrell, Harriet R. Huber, T. James Lewis, and David G. Ainley Seasonality of Summer Habitat and Social System of Red Phalaropes (abstract only) . 187 By Douglas Schamel and Diane Tracy Availability and Utilization of Invertebrates as Shorebird Food on a Humboldt Bay Mudflat (abstract only) . 189 By L. F. Carrin, N. D. Holmberg, and S. W. Harris Flocking Behavior in Wintering Dunlin (abstract only) . 191 By S. Shanewise and S. G. Herman Biology of Shorebirds Summering on Enewetak Atoll . 193 By Oscar W. Johnson Winter Ecology of a Black Oystercatcher Population . 207 By E. B. Hartwick and W. Blaylock Feeding Ecology of Three Species of Plovers Wintering on the Bay of Panama, Central America . 217 By Joseph G. Strauch, Jr. and Lawrence G. Abele Territoriality in Non-Breeding Shorebirds . 23 1 By J. P. Myers, P. G. Connors, and F. A. Pitelka The Energetics of Foraging by Redshank, Tringa totanus . 247 By J. D. Goss-Custard Summarizing Remarks, Part 2 . 259 By John A. Wiens iv Studies in Avian Biology No. 2:v-vii, 1979. PREFACE Early in 1976, George J. Divoky, then chairman of the Pacific Seabird Group, reported that the governing committee of the PSG had decided to sponsor a symposium on shorebirds at its next annual meeting, in January 1977. He invited me to organize it. I welcomed the opportunity for several reasons. First, I had attended the PSG’s second annual meeting in December 1975 and found the program and its attendants to be a good mix of interests in research on marine birds. Attendance by representatives from federal and state agencies, both active field workers and administrators, was better than at most ornithological meetings. Moreover, the membership as a whole evinced a sense of mission with regard to environmental welfare of marine birds, reflecting the ongoing and prospective research on their ecology and conservation sponsored by government agencies. All this boded well for a program on shorebirds that would direct attention to matters of habitat critical for shorebirds as well as their basic biology. Second, in the prior 20 years or so, research on basic ecology and behavior of shorebirds had advanced more rapidly on their breeding grounds than on migra- tory and wintering grounds, and some balancing of attention was clearly in order. This need was made all the more conspicuousby the simple fact that shorebirds spend 9-11 months on the latter, only l-3 months on the former. A symposium reflecting current research interests on their nonbreeding areas could help to improve the balance. Third, in view of the expanding front of research on shorebirds on the two sides of the north Atlantic, especially their migration patterns and winter habitat use, the time was clearly opportune for a review of parallel needs along the Pacific Coast. The western European community is well ahead for several reasons-its relatively compact geography, the numbers of active field observers, the magni- tude ot their “ringing” programs, and the tradition of winter-season travel by ornithologists to southern Europe and Africa. By 1970, the surge of interest in shorebirds in Great Britain led to the organization of a Wader Study Group, with its own bulletin (no. 22 issued in August 1978). Along the Pacific Coast, by comparison, informational and manpower resources for research on shorebirds are limited, and to date, both geography (bear in mind distances on our long, linear coast) and politics appear to discourage the sort of international collabo- ration needed to address problems of habitat needs and migration patterns of shorebirds. Still, the Pacific Coast is not without some bright spots of accom- plishments: The California Shorebirds Study, a cooperative program initiated with concern for preservation of wetland habitats and concluded in 1973 with a 275page report, represents the only systematic and intensive use of shorebirds as indicators yet undertaken in the New World (see papers by Jurek and Speth). The Offshore Continental Shelf Environmental AssessmentProgram in Alaska, initiated in 1975 and for which the Bureau of Land Management is primary spon- sor, representsa massive effort to provide baseline data and to assessprospective impact of coastal developments on biota generally, including shorebirds. A vol- canic rush of new information is forthcoming. Questions of focus and follow-up for all this work remain, in California, Alaska, and elsewhere. It seemed clear that a symposium could help to bring all these matters into better perspective for both field workers and government agencies. V Accordingly, I sought papers on various aspects of shorebird biology and hab- itat conservation, which the contents of this volume illustrate well. By late sum- mer, 1976, the developing program for the symposium spilled over the single day initially planned, and an extra half day was added. Time would not have allowed more papers than the contents of this volume. Yet initially, I did hope that more papers would result from my solicitations to Latin American workers and to representatives of government agencies responsible for coastal habitats in Ore- gon, Washington, British Columbia, and Alaska, but my success in these two respects was only modest. With regard to Latin America, survey work of the sort illustrated by papers of Hughes (Peru) and of Smith and Stiles (Costa Rica) badly needs doing in other sectors of the Pacific Coast. Existing distributional information is still relatively rough, and data for a picture of relative abundance in species such as the Sand- erling with immensely broad latitudinal distribution are scant or non-existent. Further, it appears that some discontinuities in coastal occurrence may reflect migratory landfalls or stagingareas after or before long distanceflights. A possible example is the Knot. It is important to try to identify these critical coastal sectors. Still further, more primary work as well as a summary for the occurrence of nonbreeders during the boreal summer are needed for tropical and austral coasts. The paper by Johnson for nonbreeders on a Pacific atoll suggestsproblems of interest beyond mere distribution. A coordinated program for year-round cen- susingof selected sectors spacedalong the Pacific Coast from San Diego to Tierra de1 Fuego would serve as an essential foundation for more sophisticatedwork on shorebird biology as well as on assessmentand conservation of coastal habitats. With regard to the North American coast north of California, the greatest amount of work is of course going on in Alaska, illustrated here by four papers. I had hoped to get a more general paper reviewing problems of coastal habitat classification and preservation as seen in these critical times for that state.