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1 April 2009 Sex and Age-Specific Annual Survival in a Neotropical Migratory Songbird, the Purple Martin (Progne subis)
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We estimated apparent annual survival probability of adult Purple Martins (Progne subis) using a 14-year data set from a population in northwestern Pennsylvania. We modeled age, sex, and year effects on adult survival using known-age birds (585 males and 392 females) first banded or resighted as one-year-olds in two core breeding colonies. We resighted banded birds at (1) the two core breeding colonies, (2) other breeding colonies within 50 km of the core colonies, and (3) a large premigratory roost that attracts adult Purple Martins from colonies ≤200 km away. Apparent annual survival probability for one-year-olds increased by 0.08 when we included encounters outside the core colonies. Survival probability for older males and females was largely unaffected, a result of their high breeding-site fidelity. The model with age-specific survival (1 year old, 2–4 years old, ≥5 years old) and an age*sex interaction had the strongest support when all encounters were included. Apparent annual survival of one-year-old females (0.48 ± 0.03 [SE]) was lower than that of one-year-old males (0.59 ± 0.02), but we detected no sex differences in survival among older birds (2–4 years old: females, 0.64 ± 0.02; males, 0.62 ± 0.02). We found evidence of senescence, because birds at least five years old had lower apparent survival (females: 0.51 ± 0.06; males: 0.52 ± 0.05). Fully time-dependent models had low support, including those evaluating the relationship between annual variation in prevalence of West Nile virus and the El Niño Southern Oscillation Index, a key climate variable.

© 2009 by The American Ornithologists' Union. All rights reserved. Please direct all requests for permission to photocopy or reproduce article content through the University of California Press's Rights and Permissions website,
Bridget J. M. Stutchbury, James R. Hill, Patrick M. Kramer, Scott A. Rush, and Scott A. Tarof "Sex and Age-Specific Annual Survival in a Neotropical Migratory Songbird, the Purple Martin (Progne subis)," The Auk 126(2), 278-287, (1 April 2009).
Received: 29 February 2008; Accepted: 1 October 2008; Published: 1 April 2009

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