The social and genetic mating system in flickers linked to partially reversed sex roles

Abstract

The type of social and genetic mating system observed in birds is influenced by the need of both sexes to provide parental care. In woodpeckers, unlike most birds, females are partially emancipated as males provide most of the care including nocturnal incubation. We analyzed the mating system of northern flickers Colaptes auratus and used microsatellite markers to assess parentage of 326 nestlings from 46 monogamous broods and 41 nestlings from 7 polyandrous broods. No cases of extrapair paternity were found in monogamous broods, but there was one such case in the brood of a secondary male of a polyandrous female. Intraspecific parasitism lead to 17% of broods containing at least one parasitic egg. The identity of the parasitic female was determined in 5 cases to be a close neighbor with a mate and clutch of her own. Between 0% and 5% of females annually were polyandrous with the timing of the 2 nests slightly staggered. Polyandrous females were older than average females in the population, and their primary males were older than secondary males. Polyandrous females raised nearly twice as many (10.8) nestlings compared with monogamous females (5.5). Although most female flickers are strictly socially and genetically monogamous, some can benefit from engaging in the alternate reproductive tactics of polyandry and brood parasitism. Therefore, at least in flickers, such tactics of laying eggs in multiple nests are not the result of poor-quality females "making the best of a bad situation" but are a way to increase reproductive success.