1397 LOCAL ANNUAL SURVIVAL AND SEASONAL RESIDENCY RATES OF SEMIPALMATED SANDPIPERS (CALIDRIS PUSILLA) IN PUERTO RICO SѢsan M. Rice, 1,4 Jaime A. Collazo, 2,5 Mathew W. Alldredge, 2 Brian A. Harrington, 3 and Allen R. Lewis 4 1 U.S. Fish and Wildlife Service, Eastern Shore of Virginia National Wildlife Refuge, 5003 HalleĴ Circle, Cape Charles, Virginia 23310, USA; 2 U.S. Geological Survey, North Carolina Cooperative Fish and Wildlife Research Unit, North Carolina State University, Raleigh, North Carolina 27695, USA; 3 Manomet Center for Conservation Sciences, Manomet, MassachuseĴs 02345, USA; and 4 Department of Biology, University of Puerto Rico, Mayagüez Campus, Mayagüez 00681, Puerto Rico Aяstract.—We report seasonal residency and local annual survival rates of migratory Semipalmated Sandpipers (Calidris pusilla) at the Cabo Rojo salt flats, Puerto Rico. Residency rate (daily probability of remaining on the flats) was 0.991 ± 0.001 ( x ± SE), yielding a mean length of stay of 110 days. This finding supports the inclusion of the Caribbean as part of the species’ winter range. Average estimated percentage of fat was low but increased throughout the season, which suggests that birds replenish some spent fat reserves and strive for energetic maintenance. Local annual survival rate was 0.62 ± 0.04, within the range of values reported for breeding populations at Manitoba and Alaska (0.53–0.76). The similarity was not unexpected because estimates were obtained annually but at opposite sites of their annual migra- tory movements. Birds captured at the salt flats appeared to be a mix of birds from various parts of the breeding range, judging from morphology (culmen’ s coefficient of variation = 9.1, n = 106). This suggested that origin (breeding area) of birds and their proportion in the data should be ascertained and accounted for in analyses to glean the full conservation implications of winter-based annual survival estimates. Those data are needed to unravel the possibility that individuals of distinct popula- tions are affected by differential mortality factors across different migratory routes. Mean length of stay strongly suggested that habitat quality at the salt flats was high. Rainfall and tidal flow combine to increase food availability during fall. The salt flats dry up gradually toward late January, at the onset of the dry season. Semipalmated Sandpipers may move west to other Greater Antilles or south to sites such as coastal Surinam until the onset of spring migration. They are not an oversummering species at the salt flats. Conservation efforts in the Caribbean region require understanding the dynamics of this species throughout winter to protect essential habitat. Received 7 December 2005, accepted 30 December 2006. Key words: apparent survival, Calidris pusilla, Caribbean, mark–recapture, migra- tion, Semipalmated Sandpiper, stopover, winter distribution. T asas de Supervivencia Anual Local y de Residencia Estacional de Calidris pusilla en Puerto Rico ResѢmen.—Reportamos la tasa estacional de residencia y de supervivencia anual local para los playeros migratorios Calidris pusilla en las Salinas de Cabo Rojo, Puerto The Auk 124(4):1397–1406, 2007 © The American Ornithologists’ Union, 2007. Printed in USA. 5 Address correspondence to this author. Present address: Department of Zoology, Campus Box 7617, North Carolina State University, Raleigh, North Carolina 27695, USA. E-mail: jaime_collazo@ncsu.edu Downloaded from https://academic.oup.com/auk/article-abstract/124/4/1397/5562825 by guest on 02 June 2020