Division of labour during incubation in a woodpeckerColaptes auratuswith reversed sex roles and facultative polyandry

Abstract

The contribution of males to incubation has rarely been studied in altricial birds because the pursuit of extra mating opportunities is believed to conflict with incubation. Woodpeckers show reversed sex roles in parental care with males doing most of the nest construction, incubating and brooding of the young while females may be polyandrous. I investigated incubation by each sex at 71 monogamous and four polyandrous nests of the Northern FlickerColaptes auratus, predicting that males would contribute to incubation according to their energy reserves (body condition) whereas females would contribute based on alternate reproductive opportunities. Nest attendance was 99% with males contributing a mean of 66% of the total incubation including nocturnal incubation. The length of daytime bouts averaged about 2 h and did not differ between the sexes. Consistent with predictions of investment strategies, structurally larger males and those in poorer body condition incubated less than smaller males, perhaps because they required more recess time to forage or to conserve energy. Older females contributed less incubation than young females and polyandrous females contributed less incubation at their secondary nests than monogamous females. Incubation period, nest depredation rate and hatching success were not influenced by bout length, number of bouts or relative contribution of the sexes. Hatching success was 86% at nests of both monogamous and polyandrous females because males compensated for reduced female participation. Because incubation of the sexes is compensatory and not additive, incubation pattern did not influence short‐term reproductive success. I conclude that males invest in incubation according to their energy needs, and females may adjust their contributions based on alternate reproductive tactics.