Exploring the mechanisms of coordinated chick provisioning in the Manx shearwater (Puffinus puffinus)

Many species that provide care for their offspring in tandem with a
partner coordinate their activities to maximise the efficiency of their
investment. However, it is not well known exactly how this coordination is
achieved. Manx shearwaters Puffinus puffinus are Procellariiform seabirds
that exhibit a dual foraging strategy during chick provisioning in which
long foraging trips to maintain condition are alternated with short,
frequent trips to feed the offspring. This strategy is employed in a
coordinated manner between the parents, with one making short trips while
the other takes a single long trip. Previous work revealed that a
complementary switch in foraging trip type is initiated by the parents
following a synchronous visit to the nest. We used a combination of
observational data and an experimental manipulation to examine the
mechanisms that may underlie this behaviour. Specifically, we investigated
the evidence that physical reunion is necessary to induce a switch in trip
type, whether parents change their behaviour to maximise the probability
of partner encounter, and whether indirect cues gained from the chick
could inform a switch in behaviour. In our experimental approach, we
manipulated the information adults had available to them by
supplementarily feeding chicks to alter their begging behaviour. We found
no support for the role of physical reunion or indirect cues in the
coordination of care in this species. We discuss the possibility that the
patterns of alternated provisioning observed during chick rearing in Manx
shearwaters may emerge through entrainment during the well-coordinated
incubation period preceding chick provisioning.