It is good to be average: Ecological correlates of breeding phenology in an Arctic seabird, Alle alle (Dovekie)

Recognising importance of deviation from a population mean in an
animal's behavior is not only necessary to understand the evolution
and stability of the whole system but also to predict the future of a
population in an altering environment. Arctic seabirds are expected to
exhibit high synchronization in timing of breeding at the population
level, due to highly seasonal and harsh environmental conditions.
Nevertheless, even in such a highly synchronized system, there are always
some earlier and later breeders, and what causes this inter-pair variation
remains an intriguing question. Using a set of eight years of data on the
dovekie (Alle alle), a small Arctic seabird, we examined potential drivers
of the observed distribution of breeding phenology. We found that dovekie
pairs were quite repeatable in their phenology, and preserved their
phenological status, with their chicks hatching consistently before,
during, or after the population median date for hatching, despite that
calendar position of the median shifted between years. This would suggest
that the timing of breeding is associated with some pair characteristics,
either via properties of the nest or/and some partners traits. However,
breeding phenology of the pair was not dependent on nest location, neither
pair bond duration nor morphological similarity of the partners.
Importantly, timing of breeding was negatively associated with chick
growth rate, indicating fitness consequences of phenology. Our simulation
further suggests that chance of fledgling survival in the context of
predation may be the highest for the chicks that hatched during the peak
of hatching period. While our results suggest that the timing of the
breeding is important for the reproductive outcome, further research is
required to determine the drivers of the repeatability within the dovekie
pairs.