Data from: Phenotypic plasticity or evolutionary change? An examination of the phenological response of an arctic seabird to climate change

1. Phenological adjustments are an important aspect of a population’s
response to climate change. Changes in phenology can occur through either
individual plasticity or evolutionary change within populations. Few
studies have investigated both these processes in Arctic environments. 2.
Using 42 years of individual and pedigree data, we evaluated the
contribution of plasticity and evolution to variation in breeding
phenology at a colony of a high Arctic sea-ice obligate seabird, Mandt’s
black guillemot (Cepphus grylle mandtii). Mean clutch initiation (first
egg in a clutch) advanced 7.8 days, and both environmental (snowmelt) and
demographic (years of breeding experience) factors varied among years. 3.
Earlier phenology was associated with earlier snowmelt and experienced
mothers. Females advanced phenology at different rates as they aged but at
similar rates in response to variation in snowmelt. Heritability of clutch
initiation was negligible, and there was no evidence of evolution
contributing to phenological changes. 4. Earlier laying was associated
with increased annual number of fledglings and annual adult survival at
the individual level suggesting that the phenological changes are adaptive
and are driven by phenotypic plasticity, but not genetic responses. 5. We
propose that species with a constrained breeding season (like many Arctic
species) may have a limited ability beyond existing plasticity to respond
to changing environmental conditions.