Nest sanitation in response to short- and long-term changes of brood size: males clean more in a sex-role-reversed species

• We examined nest sanitation in a sex-role-reversed species, the northern flicker.
• We altered energy demands by manipulating short- and long-term brood size.
• Males removed more faecal sacs than females.
• Females, but not males, with high corticosterone levels (stress) removed fewer sacs.
• Single males removed fewer faecal sacs than paired males by trading off provisioning.

Nest sanitation is an understudied form of parental care that may improve offspring fitness by reducing microbes and ectoparasites in the nest. Many species clean nests, but it is unknown whether parents respond flexibly to various costs and benefits when deciding how much effort to invest. We experimentally manipulated brood size in the short term and in the long term in a cavity nester, the northern flicker, Colaptes auratus, to test whether parents alter their sanitation effort in response to brood demands. Males generally removed more faecal sacs than females at all treatments and in most cases, faecal removal rates were proportional to feeding rates in control and experimental broods. The rate of sac removal was negatively correlated with feather corticosterone in females but not in males. Males maintained higher faecal removal rates than females to enlarged broods and were more flexible than females in altering their sanitation effort relative to their feeding rate. Single males, but not females, removed fewer faecal sacs than paired males, suggesting that males reduce nest sanitation effort in times of high nestling demands if it helps maximize fledging success. Across taxa, the sex that invests the most in other forms of parental care also seems to perform more nest sanitation, and future studies should test how parents value it differently depending on brood demands and intrinsic factors.