The influence of body condition on local apparent survival of spring migrant Sanderlings in coastal North Carolina.
Abstract. Many shorebirds are long-distance migrants, and they depend upon widely spaced stopover sites for refueling during their annual migrations. Two competing hypotheses attempt to explain stopover duration: one predicts departure based on time minimization (timeselection hypothesis) and the ot...
| Main Authors: | , , |
|---|---|
| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
2003
|
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1089.274 http://obpa-nc.org/DOI-AdminRecord/0054794-0054802.pdf |
| Summary: | Abstract. Many shorebirds are long-distance migrants, and they depend upon widely spaced stopover sites for refueling during their annual migrations. Two competing hypotheses attempt to explain stopover duration: one predicts departure based on time minimization (timeselection hypothesis) and the other predicts departure on the basis of maximum energy gain (energy-selection hypothesis). During spring 1993, we tested these hypotheses during a markresight study of migrant Sanderlings (Calidris alba) at Portsmouth Island, North Carolina. We individually color-banded 204 Sanderlings and used capture-recapture methods to estimate local apparent survival during 10 five-day intervals from late April to mid-June. We found that survival rates were best modeled as a decreasing quadratic time trend; a linear time trend and period-specific survival rates received little support. We found no evidence that either body mass or a simple body condition index better explained survival rates. Our estimates of the 5-day local survival rates of Sanderlings at Portsmouth Island remained relatively high ((O; > 0.80) through late May, after which they dropped rapidly as birds left the area. The periodspecific conditional resighting probability was 0.39 (SE = 0.03). Our results do not provide strong support for either the time-or energy-selection hypotheses and hint that studies of migratory behavior need to be conducted even more intensively and across much larger regions in order to better understand the underlying factors. Key words: body condition, Calidris alba, North Carolina, Sanderling, shorebird, survival. Influencia de la Condici6n Fisica sobre las Tasas de Residencia de Calidris alba durante la Migraci6n de Primavera en la Costa de Carolina del Norte Resumen. Muchos playeros migran largas distancias y dependen de areas ampliamente esparcidas para hacer escalas durante sus migraciones anuales. En estas areas, los playeros reabastecen ripidamente sus reservas energ6ticas antes de partir hacia la pr6xima parada. Existen dos ... |
|---|