Arctic seabirds show individual variation in foraging responses to glacial conditions without consequences for reproductive output

Behavioural plasticity is predicted to be the primary mechanism by which
long-lived species continue to access resources under rapid climate
change. Plasticity will be particularly important at highly dynamic,
prey-rich foraging areas such as upwelling fronts of marine-terminating
glacier in the high Arctic, where profitability varies significantly
across space and time. Understanding individual variation in plasticity is
crucial to understand populations adaptability to future climate
scenarios. By analysing GPS data from 186 black-legged kittiwakes (Rissa
tridactyla) breeding in the high Arctic over six years, we quantified
individual variation in behavioural plasticity in use of glacial fronts
and its relationship with the number of chicks produced. Variation in the
relationship between glacial use and levels of discharged meltwater was
primarily explained by differences in food availability between years.
Whereas individuals spent more time at glaciers with increasing discharge
when zooplankton biomass was low in the fjord, the probability of glacial
front use decreased in years when food was more abundant despite high
discharge and likely good conditions at the front. Interestingly, neither
glacial use nor plasticity in foraging during the breeding season
correlated with the number of surviving chicks, suggesting that all
individuals still obtained enough food for reproduction. With increasing
rate of glacier retreat and shifts in food availability, less plastic
individuals or those reliant on glacial fronts may face pressure in
finding food and may thereby experience long-term declines in reproductive
success. Understanding and quantifying the complex nature of individual
variation in plasticity will provide more detailed insights into how
species will survive in rapidly changing environments.