Food abundance, kittiwake life histories, and colony dynamics in the Northeastern Pacific:implications of climate change and regime shifts

Black-legged kittiwakes Rissa tridactyla in the Northeastern Pacific will increasingly experience climate-induced changes in the variability of forage fish, which will influence both the quantity and quality of food and may thus alter the population dynamics of kittiwake colonies. However, the relative roles of individual- and population-level traits in determining colony dynamics and risk of extinction are still unclear. We combined models of components of the Pacific kittiwake life history with empirical data linking physiological stress and food abundance to provide a unified treatment of kittiwake colony dynamics. We simulated the dynamics of colonies with high, medium and low responsiveness of productivity to variation in nutritional stress in breeding birds, using data from Alaskan colonies. We found that the risk of quasi-extinction strongly decreased with a moderate increase in the potential number of yearly immigrants. Pre-breeding mortality as a function of growth during development had only a marginal role in determining median number of breeding pairs over simulation time. We predict that temporal auto - correlation of colony-wide average productivity and high nutritional stress, particularly if consistent over time, will increase quasi-extinction risk. Our work shows that colonies with low productivity have little chance of persistence even when survival of pre-breeding and breeding birds is high, and that the nature of the temporal auto-correlation of food conditions and productivity is crucial to understand the effect of environmental fluctuations, regime shifts, and climate change on population dynamics of kittiwakes. We use the model to highlight the most valuable future empirical studies.