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1 October 2002 Extreme Between-Year Variation in Productivity of a Bridled Titmouse (Baeolophus wollweberi) Population
Beth J. Christman
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Environmental variability affects life-history decisions such as allocation of resources to reproduction. However, in the case of small passerine birds, pairs that acquire a territory do not usually skip a breeding season. This study presents breeding-success data from two contrasting years for a population of Bridled Titmice (Baeolophus wollweberi). During an El Niño year (1998), 20 pairs attempted to breed, and 85% were successful. Survival of juveniles from 10 banded broods through nutritional independence was 100%, excluding one depredated nest. Breeding success was much lower in the following La Niña drought year. Fifty-seven pairs established territories in the study area. Twenty-seven never progressed to nest building. Thirteen pairs were successful; survival of young from banding to nutritional independence was 41.4%. An average of 0.47 fledglings per breeding pair was produced in 1999, compared to 4.40 the previous El Niño year. This study examines possible adaptive significance of forgoing breeding in a poor year.

Beth J. Christman "Extreme Between-Year Variation in Productivity of a Bridled Titmouse (Baeolophus wollweberi) Population," The Auk 119(4), 1149-1154, (1 October 2002).[1149:EBYVIP]2.0.CO;2
Received: 29 January 2001; Accepted: 17 July 2002; Published: 1 October 2002
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