A guide to Pigeon Guillemot nest sites on South Marble Island, Glacier Bay, Alaska

Zador, S

The pigeon guillemot (Cepphus columba) is a widely distributed seabird in the North Pacific and common in coastal waters of Alaska. Guillemots are abundant seabirds breeding in Glacier Bay, Alaska, but little is known about the status of their population. This guide documents the location of guillemot nest sites on South Marble Island, which is an important seabird colony and Steller sea lion (Eumetopias jubatus) haul-out located in central Glacier Bay. The island has been closed to foot traffic for over 25 years to reduce disturbance to the breeding seabirds and the federally-protected Steller sea lions. During the course of other research on South Marble Island, I photographed and monitored some accessible nest sites. This work was incidental to other research activities, and nest sites were checked as time allowed. To minimize disturbance to the breeding birds, nests were checked at most once per week during incubation and no more than once every two days during the chick-rearing stage. Some nest sites were checked only once. Guillemots typically nest in crevices along rocky coastline. In this guide, a nest site is defined as a protected crevice or recess in which one or more guillemots, guillemot eggs, or guillemot chicks have been observed. It also includes crevices that resemble typical guillemot nest sites, but were not active this year. These sites are subjectively defined as a protected crevice or recess containing a flattened area, sometimes lined with small stones, suitably-sized for a guillemot nest. I have produced this guide to document the status of pigeon guillemot nest sites on South Marble Island and to aid in the relocation of nest sites in future studies. Ultimately, this guide may serve as a template for a more complete guide to guillemot nest sites in Glacier Bay, as a repository of scientific data on this important population, and as a source of information for managing human activities near nest sites. The guide is organized in three sections