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1 May 2012 Within-Year Survival of Nonbreeding Crested Caracaras
James F. Dwyer, James D. Fraser, Joan L. Morrison
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Abstract

Many birds do not breed in the year(s) immediately following independence from parental care. Instead, they spend time as immatures attaining adult plumage and spend time as floaters searching for an opportunity to breed. Floaters are nonbreeding adults. Survival during this period often is poorly understood because immatures and floaters can be secretive and range widely, making them difficult to track. From July 2006 through March 2009, we used radio-tracking data collected by aerial telemetry to estimate survival of 58 nonbreeding Crested Caracaras (Caracara cheriway). Based on an information-theoretic approach, the best-supported models indicated differences in monthly survival, which was lowest (0.953) during the peak of breeding (December–January), slightly higher (0.984) during the remainder of the breeding season (October, November, February, March), and highest (0.995) during the nonbreeding season (April–September). We identified “life stage” as juvenile, immature, or floater on the basis of plumage. We found no effect of sex or life stage on monthly or annual survival, and annual survival was intermediate (0.826) between existing estimates for breeding caracaras (0.876 for males and 0.906 for females) and the dependent juveniles (0.694) of breeding caracaras. None of the birds we tracked nested during our 33-month study. Our findings provide unique insight into reduced survival of nonbreeding individuals during the period when the remainder of the population breeds, and the long-term persistence of individual floaters supports the assertion of previous authors that all breeding habitat is occupied.

© 2012 by The Cooper Ornithological Society. 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, http://www.ucpressjournals.com/reprintInfo.asp.
James F. Dwyer, James D. Fraser, and Joan L. Morrison "Within-Year Survival of Nonbreeding Crested Caracaras," The Condor 114(2), 295-301, (1 May 2012). https://doi.org/10.1525/cond.2012.110065
Received: 6 May 2011; Accepted: 1 October 2011; Published: 1 May 2012
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