Wintering Ecology of Buff-Breasted Sandpipers (Tryngites subruficollis) in Southern Brazil
AuthorDe Almeida, Juliana B.
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Buff-breasted Sandpipers (<italic>Tryngites subruficollis</italic>) are a medium-sized sandpiper that suffered a steep population decline during the last century. Current estimates of population size are at least one order of magnitude smaller than historical estimates. The continued decline in population size has resulted in Buff-breasted Sandpipers being recognized world-wide as a species of critical conservation concern. Yet, little is known about their ecology at wintering sites and about their population dynamics. In this dissertation, I present results on within- and among-year density trends, life-history strategy, molt, body condition and population dynamics of Buff-breasted Sandpipers wintering in southern Brazil. Additionally, I provide a discriminant function to accurately sex Buff-breasted Sandpipers using morphometric measures.I estimated density trends of Buff-breasted Sandpipers at three wintering sites, Lagoa do Peixe National Park (LPNP), Ilha da Torotama (IT) and Taim Ecological Station (TES). Density was highest at IT, but was closely followed by LPNP. Buff-breasted Sandpipers were absent from TES during most of the study. Because of the consistency of use, and high densities at LPNP and IT, I suggest that these sites be included in any management action directed toward conservation of the species.Results in molt schedule, as well as arrival and departure patterns at LPNP indicated that males and females have different life-history strategies. Males molted wing and tail feathers faster than females, finishing molt approximately one month before females. This difference mirrored the difference in departure from the wintering grounds: males depart one month earlier than females. Moreover, sex ratio at LPNP was female biased and males were more prone to leave the site in any given month. The between-sex difference in life-history strategy and female bias at the north end of the wintering range suggest that sexual segregation in Buff-breasted Sandpipers is opposite to what would be predicted by sexual segregation theory: male Buff-breasted Sandpipers winter further south instead of further north as would be predicted.Apparent annual survival of Buff-breasted Sandpipers is equivalent to or higher than survival rates reported for other shorebirds. Additionally, males had lower apparent annual survival and a higher temporary emigration rate than females. Differences in apparent annual survival between sexes may result from the short-term nature of this study and/or higher emigration rate of male Buff-breasted Sandpipers. Therefore, future long-term studies utilizing mark-recapture techniques are critical for understanding variation in Buff-breasted Sandpipers annual survival. This study demonstrated that wintering sites provide the best location for estimating annual survival.