Temporal change in the contribution of immigration to population growth in a wild seabird experiencing rapid population decline

The source-sink paradigm predicts that populations in poorer-quality habitats (“sinks”) persist due to continued immigration from more-productive areas (“sources”). However, this categorisation of populations assumes that habitat quality is fixed through time. Globally, we are in an era of wide-spread habitat degradation, and consequently, there is a pressing need to examine dispersal dynamics in relation to local population change. We used an integrated population model to quantify immigration dynamics in a long-lived colonial seabird, the black-legged kittiwake Rissa tridactyla, that is classified as globally “Vulnerable”. We then used a transient life table response experiment to evaluate the contribution of temporal variation in vital rates, immigration rates, and population structure to realised population growth. Finally, we used a simulation analysis to examine the importance of immigration to population dynamics. We show that the contribution of immigration changed as the popula...