The Influence of Body Condition on Local Apparent Survival of Spring Migrant Sanderlings in Coastal North Carolina

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[edit] Author(s)

  • Dinsmore, S. J.
  • Collazo, J. A.

[edit] Journal

Condor 105.3 (2003): 465-73

[edit] Keywords

body condition calidris alba north carolina sanderling shorebird survival plasma-lipid metabolites western sandpipers semipalmated sandpipers stopover ecology marked animals shorebirds migration alba mass

[edit] 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 (time-selection 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 mark-resight 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 (phi(i) > 0.80) through late May, after which they dropped rapidly as birds left the area. The period-specific 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.

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