Causes and consequences of divorce in the Tree Swallow.

LLAMBÍAS P.E, WREGE P.H. AND WINKLER

Illinois, USA

Congreso; 121st Stated Meeting of the American Ornithologists’ Union.; 2003

American Ornithologist's Union

If a pair of monogamous birds survives the non-breeding season they can breed againtogether (remate) or they can breed with a different partner (divorce). Here we describe thecauses and consequences of divorce in an aerial insectivore, the Tree Swallow Tachycinetabicolor based on a 14-year study of a nest-box population in Ithaca, New York. We limitedour study to pairs where both sexes were banded and survived to the following breedingseason (n=214). A total of 163 pairs divorced between breading seasons, resulting in anoverall divorce rate of 76%. Pairs that subsequently divorce produce fewer fledglings thanpairs that re-mate, and they were more likely to include younger females than pairs thatremained together the following season. On the other hand, clutch size did not differbetween divorcing and remating pairs. After divorce or remating neither females nor malesincreased their breeding success, suggesting that divorce and mate-retention are notstrategies to increase breeding performance. 81% of the pairs that re-mated and 76% of themales that divorced bred in the same or adjacent boxes, while 74% of the females thatdivorced moved more than 50 m. We suggest that divorce in our population is aconsequence of female breeding dispersal caused by low breeding success.