The bottom line for seabirds is how their populations change over time. We have found that different colonies can have markedly different patterns of population change-- even colonies that are relatively close to one another. For example, in lower Cook Inlet, populations of Common Murres and Black-legged Kittiwakes have declined by more than 80-90% at Chisik Island during the past 20 years; while just across the inlet at Gull Island, the same species' populations have increased by more than 90% over the same time period. The differences in population dynamics appear to be related to persistent differences in availability of food around these colonies (poor food supplies at Chisik, good supplies at Gull Island).