Factors affecting recovery of pigeon guillemot populations in Prince William Sound, Alaska 1995 - 2000 [Unformatted Data]

The objective of this component was to evaluate the breeding and feeding ecology of pigeon guillemots (Cepphus columba) with respect to the abundance and availability of forage fish in the near shore environment. We monitored the reproductive success of 50 guillemot nests at Naked Island, Prince William Sound. Data from numerous sources indicate that there has been a change in the Gulf of Alaska marine ecosystem that began around the late 1970s, which in turn has probably affected marine bird populations. The population of pigeon guillemots in Prince William Sound decreased from about 15,000 in the early 1970s to less than 5,000 in the 1990s. Study colonies at Naked Island and four neighboring islands in Prince William Sound have shown a similar trend since the late 1970s. During this period, the diet of pigeon guillemot chicks on Naked Island also changed. In the late 1970s Pacific sand lance (Ammodytes hexaptenu), a schooling forage fish, dominated the chick diet. In the 1990s chick diet has been dominated by fish that live on or near the bottom, such as gunnels, pricklebacks, sculpins, and cod-like fish. The correlation between percent sand lance in the chick diet and the total guillemot population is strong, and we suggest that there is a link between the change in diet and the population decline.

Previous related projects have been funded by the Trustee Council. Oakley and Kuletz (1996) undertook a study in 1989-1990 to compare various population and reproductive parameters of pigeon guillemots before (Oakley and Kuletz 1979, Kuletz 1981, 1983, Oakley 1981) and after the spill. Also, Project 93034, an extensive survey of pigeon guillemot colonies throughout Prince William Sound, was conducted during the summer of 1993 (Sanger and Cody 1994).