First explorations: ontogeny of central-place-foraging directions in two tropical seabirds

A widespread hypothesis for the ontogeny of behaviour and decision-making
is the early-exploration-later-canalization hypothesis. It postulates that
juveniles are more exploratory and adults more consistent in their
behavior. In addition, it is often assumed that naïve juveniles could
overcome the costs of individual experience building by copying more the
decisions of others than adults (early-conformism-later-self-defining
hypothesis). Here we compare the central-place-foraging movements of
adults and post-fledging juveniles in their first flights around the
colony before dispersal and migration, in two sympatric species of
tropical seabirds: red-footed boobies and great frigatebirds. Using GPS
records of individual movements, we analyzed the foraging directions of
seabirds from the colony across successive trips. Juveniles of both
species showed significant within-individual consistency in foraging
direction but at lower levels than adults. Juveniles leaving the colony
within the same time-window showed significant but low between-individual
resemblance in foraging direction, at levels similar to adults. In both
species, homing efficiency was lower in juveniles than in adults. Juvenile
foraging directions were initially influenced by wind conditions,
particularly in low-wing-loading frigatebirds. Wind conditions
progressively lost influence on juvenile foraging directions during their
first weeks of flights. In contrast within-individual consistency,
between-individual resemblance and homing efficiency did not show signs of
progression in juveniles. Our results support the
early-exploration-later-canalization hypothesis but not the
early-conformism-later-self-defining hypothesis. Relaxed constraints on
self-feeding efficiency could favour high variability in post-fledging
tropical seabirds. Our simple approach could be applied to further test
these hypotheses by comparing strategies across a wide range of
central-place foragers.