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.