Surveys for seabirds at sea can reveal much about seabird foraging behavior and about constraints operating on seabirds at particular colonies. For example, surveys in lower Cook Inlet (figures below) reveal that Common Murres from the Barren Islands (in lower left of figures) are found in large numbers on the water immediately adjacent to the colony islands, and also to the north-- both offshore and inshore. In general, these are also good areas for forage fish. Why?  Productivity appears to be enhanced around the colonies and near the mainland shore by local currents and tide rips, and by the abundance of shallow benthic substrates suitable for use by Pacific sand lance. Offshore, upwelling of waters at the entrance to Cook Inlet enhances overall production of everything from phytoplankton to seabirds. These patterns in lower Cook Inlet are persistent features of the local ecosystem that murres must deal with every year. For example, many murres from the Barren Islands must range considerable distances to obtain food-- about 2-3 times further than murres in Kachemak Bay. But since food appears to be predictable and abundant to the north, it is well worth the effort.

Distribution of Common Murres in lower Cook Inlet, 1997-1998.