Phenological changes in response to climate change have been recorded in many organisms around the world. It’s important to understand what factors cue and/or constrain the timing of breeding for these organisms, as this period may need to be temporally coupled to seasonal availability of food resources for successful breeding. A number of environmental factors, from temperature to photoperiod, are often cited as principal drivers of breeding phenology in birds, however these hypotheses have largely gone untested in the highly variable Antarctic system.
We assembled the largest database of both wild and captive Adélie penguin breeding phenology to date, in an attempt to understand what drives breeding phenology in this Antarctic seabird. We further explore what implications this might have for potential phenological mismatch in the face of rapid climate change across the Antarctic continent. Two independent hierarchical Bayesian models were used to model breeding phenology of both wild and captive penguin populations. Effects for year, individual, and age were addressed as a part of this analysis. Distributions of breeding phenology were analyzed for potential skew, which might indicate constraints on breeding phenology within a given season.
Results/Conclusions
Our results show that neither photoperiod nor environmental variables explain the variability in breeding phenology among years or among breeding sites. Even in captivity, under controlled conditions, Adélie penguins exhibit highly variable breeding phenology from year to year. We attribute the stochastic nature of breeding phenology to the increased importance of breeding synchrony among individuals, which may facilitate predator avoidance in this highly colonial species. This is supported by a right-skewed distribution of breeding phenology in the captive environment. We suggest that the importance of this colonial breeding strategy may outweigh the importance of a ‘temporal match’ with the environment – a factor that has been largely unaddressed in phenological research. This has important implications for understanding how phenology might change through time, particularly in light of rapid climate change in many regions of the world and concerns regarding temporal mismatches with resource availability.