Extra-pair mate choice in the song sparrow (Melospiza melodia)

Caroline Elizabeth Ames
2009
Extra-pair paternity (EPP) is common in birds yet its adaptive significance remains unclear. Since the strategy of EPP is thought to carry costs, females are predicted to obtain indirect genetic benefits (e.g. 'good genes') or direct material benefits (e.g. fertility insurance) from pursuing extra-pair copulations (EPCs). Breeding synchrony may also influence the costs and benefits of EPP to males and females. I examine 'good genes' benefits of EPP and the effect of breeding synchrony on EPP in
more » ... synchrony on EPP in a socially monogamous population of song sparrows wherein 29% of 751 offspring were sired by extra-pair males. The good genes hypothesis predicts that females mate with extra-pair males that have higher expected fitness than their social mate in order to improve the fitness of extra-pair young (EPY) compared to within-pair maternal half-siblings. Using traits closely linked to lifetime reproductive success, I found no evidence that EPY were fitter than their maternal half-siblings or that extra-pair males were fitter than cuckolded males. However, I found that middle-aged males on average were 3.1 —4.7 times more likely to sire EPY than first-year males and 1.3 —2.0 times more likely to sire EPY than very old males. This is consistent with similar, well-established patterns of age-related variation in annual reproductive success in song sparrows, suggesting that male success in siring EPY is influenced by experience and ability, rather than quality. I found a significant negative relationship between breeding synchrony among neighbors and the proportion of EPY within broods of focal males. This result supports the 'mate Extra-pair paternity (EPP) is common in birds yet its adaptive significance remains unclear. Since the strategy of EPP is thought to carry costs, females are predicted to obtain indirect genetic benefits (e.g. 'good genes') or direct material benefits (e.g. fertility insurance) from pursuing extra-pair copulations (EPCs). Breeding synchrony may also influence the costs and benefits of EPP to males and femal [...]
doi:10.14288/1.0068158 fatcat:kvelc2rp6nhtdipfzpp2dk4mka