Data from: Early diving behaviour in juvenile penguins: improvement or selection processes

The early life stage of long-lived species is critical to the viability of
population, but is poorly understood. Longitudinal studies are needed to
test whether juveniles are less efficient foragers than adults as has been
hypothesized. We measured changes in the diving behaviour of 17
one-year-old king penguins Aptenodytes patagonicus at Crozet Islands
(subantartic archipelago) during their first months at sea, using
miniaturized tags that transmitted diving activity in real time. We also
equipped five non-breeder adults with the same tags for comparison. The
data on foraging performance revealed two groups of juveniles. The first
group made shallower and shorter dives that may be indicative of early
mortality while the second group progressively increased their diving
depths and durations, and survived the first months at sea. This surviving
group of juveniles required the same recovery durations as adults, but
typically performed shallower and shorter dives. There is thereby a
relationship between improved diving behaviour and survival in young
penguins. This long period of improving diving performance in the juvenile
life stage is potentially a critical period for the survival of deep avian
divers and may have implications for their ability to adapt to
environmental change.