Divorce and extrapair mating in female black-capped chickadees (Parus atricapillus): separate strategies with a common target |
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Authors: | S M Ramsay K A Otter D J Mennill L M Ratcliffe P T Boag |
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Institution: | (1) Department of Biology, Queen’s University, Kingston, Ontario, K7L 3N6, Canada, CA;(2) Biology Programme, University of Northern British Columbia, 3333 University Way, Prince George, BC, V2N 4Z9, Canada, CA |
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Abstract: | Patterns of divorce and extrapair mating can provide insights into the targets of female choice in free-living birds. In resident,
site-faithful species with continuous partnerships, the better options and the incompatibility hypotheses provide the most
likely explanations for divorce. Extrapair mating can be explained by a number of hypotheses often making similar predictions.
For example, the good genes and future partnerships hypo- theses predict similar patterns if males with good genes also make
the best future partners. By considering both divorce and extrapair mating, it may be possible to distinguish between these
comparable hypotheses. We examined natural patterns of divorce and extrapair mating in a long-term study of black-capped chickadees
(Parus atricapillus). Out of 144 partnerships over 8 years, we observed 11 divorces and 38 faithful pairs between seasons. Females usually divorced
between their first and second breeding seasons for males of higher social rank than their previous partners, had similar
reproductive success prior to divorce as females who retained their previous partners, and did not divorce on the basis of
previous reproductive success. These results confirm earlier experimental evidence that females divorce for better options.
Females who divorced were significantly more likely to have had mixed-paternity broods prior to divorce than females who stayed
with their previous partners. There was no evidence that females divorced in favour of previous extrapair partners. These
results support the good genes hypothesis for extrapair mating, suggesting that female chickadees use divorce and multiple
mating as separate strategies sharing a common target.
Received: 4 February 2000 / Revised: 20 July 2000 / Accepted: 4 September 2000 |
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Keywords: | Divorce Extrapair mating Better options Good genes Black-capped chickadees |
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