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1 February 2012 Demography and Breeding Ecology of the Critically Endangered Montserrat Oriole
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The Montserrat Oriole (Icterus oberi) is a critically endangered species, confined to a small range in the hill forests of the volcanic island of Montserrat in the eastern Caribbean. From 1998 to 2005 we studied its breeding biology and survival of adults, finding that the Montserrat Oriole has a smaller clutch, more extended parental care, and higher adult survival than do orioles nesting in the North Temperate Zone. Adults' probabilities of survival varied by year from 0.60 to 0.76 but were similar for both sexes. Average clutch size was 2.6 eggs (± 0.04 SE), and post-fledging parental care was 40 ± 5 days. We found nest success of 29% (n = 275 nests), and 87% of nest failures were due to predation by either introduced rats (Rattus sp.) or the native Pearly-eyed Thrasher (Margarops fuscatus). Most pairs initiated several nesting attempts after both failed and successful first broods, leading to an overall annual productivity of 1.2 fledged chicks per pair. Despite being able to raise up to three broods per season, the Montserrat Oriole's annual productivity was lower than that of its temperate-zone congeners, and we recommend that conservation management focus on enhancing nesting success via rat control.

© 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,
Richard I. Allcorn, Geoff M. Hilton, Calvin Fenton, Phil W. Atkinson, Christopher G. R. Bowden, Gerard A. L. Gray, Mark Hulme, Joah Madden, Elizabeth K. Mackley, and Steffen Oppel "Demography and Breeding Ecology of the Critically Endangered Montserrat Oriole," The Condor 114(1), 227-235, (1 February 2012).
Received: 22 February 2011; Accepted: 1 August 2011; Published: 1 February 2012

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