Ambient temperature and female body condition are related to night incubation behavior in wood ducks Aix sponsa

For many animals, parental care behavior is an important aspect of their life history that affects both parents and offspring. In birds, one of the most important parental care behaviors is incubation, which is costly to the parent but directly influences embryonic development and fitness of offspring. Some birds exhibit the intriguing behavior of partially incubating their eggs prior to clutch completion for only a portion of each day. This partial incubation is characterized by lower incubation temperatures and constancy than during full‐time incubation, which typically begins at clutch completion. Partial incubation may preserve the viability of eggs laid early in the laying sequence, shorten the length of the full incubation period, and/or provide a favorable microclimate to the incubating parent. It might also reduce the probability of nest predation, nest site takeover by another bird, brood parasitism, and/or predation of the adult. Although there is evidence that partial incubation is an adaptive behavior and that time invested in this behavior varies among individuals of the same species, nothing is known about what may drive this inter‐individual variation. To investigate how environmental and parental characteristics may be related to partial incubation behavior, we studied the partial incubation behavior of wood ducks Aix sponsa using artificial egg temperature loggers within nest boxes. Our results suggest that females with greater mass relative to their structural size invest more time in partial incubation. Additionally, the incubation temperature and length of on‐bouts of partial incubation increased over the course of the partial incubation period, and ambient temperature during on‐bouts was positively related to incubation temperature. Ultimately, our study suggests that characteristics of both the environment and parent may influence the partial incubation behavior of wood ducks, and improves our understanding of an important, but understudied, aspect of avian parental care.