Effects of site fidelity and breeding performance on mate retention in a short-lived passerine, the tree swallow Thachycineta bicolor

Authors

  • Paulo E. Llambías,

  • Peter Wrege,

  • David W. Winkler


P. E. Llambías (correspondence), Peter Wrege and David W. Winkler, Dept. of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA. Email: pel24@cornell.edu

Abstract

We studied the relationship among re-mating, site fidelity and breeding performance in the tree swallow Tachycineta bicolor using 16 y of data on reproductive biology in a population breeding in nest boxes near Ithaca, New York. Of 217 pairs for which both members survived the non-breeding season, 76% mated with a new partner and 24% reunited with their previous mate. Pairs did not increase their breeding success by breeding together for more than one breeding season. Males produced fewer fledglings after breeding with a new partner, but females neither increased nor decreased their success when breeding with a new mate. Females who bred with a new partner were younger than females that reunited with their previous mates, and they were more likely to move to a different nest box. Males that bred with a new mate were of similar age to males that reunited, and they did not move more often. The probability of breeding with a new partner was better predicted by female age than by previous breeding success, suggesting that re-mating was not strongly affected by past breeding performance. Because younger females change breeding sites more frequently than do older females and females that mated with a new partner were younger than females that reunited with their previous mates, we suggest that the tendency of tree swallows to change partners between years is a by-product of lower site fidelity of younger females rather than a strategy for increasing breeding success.

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