Data from: Breeding synchrony and extrapair paternity in a species with alternative reproductive strategies

Breeding synchrony may affect the tradeoff between pursuing multiple mates
and avoiding paternity loss, translating into differences in the rate of
extrapair paternity (EPP). However, diverse empirical relationships
between breeding synchrony and EPP remain challenging to explain. We
examined whether the relationship between breeding synchrony and EPP
varied with male morph, age, body size, or breeding density in the
white-throated sparrow Zonotrichia albicollis. In this species, males of
two genetically determined morphs pursue alternative mating strategies.
Breeding synchrony positively correlated with EPP within polygamous white
morph males, which have high rates of EPP and cuckoldry, but was unrelated
to EPP within tan morph males, which prioritize mate guarding and paternal
care. As previously reported, males that gained EPP were primarily white
males. Males gained EPP more often than expected by chance during their
mate’s fertile period and on neighboring territories. Since extrapair
copulation appears primarily male-driven in this species, these results
indicate that white males focus extra-pair mating effort during periods of
high synchrony and during their mates’ fertile periods, even at the
expense of paternity loss within their own nests. Breeding density, male
age, and male size did not modify the relationship between breeding
synchrony and EPP. However, older white males had higher cuckoldry rates,
perhaps reflecting declines in performance associated with senescence.
Results suggest that, even within species, mating strategy may modify how
breeding synchrony affects rates of EPP, with positive relationships
manifest only within subsets of individuals that pursue a strategy of
polygyny at the expense of paternity loss.