The Pigeon Guillemot (Cepphus columba)

From the Exxon Valdez Oil Spill Trustee Council (EVOS) Fiscal Year '95 Project Description:

"Guillemots are the most neritic members of the marine bird family Alcidae, which includes murres, puffins, and auks. Guillemots first breed at 2 years of age and adults have high annual survivorship. Young guillemots normally return to the natal area to breed. Nest site fidelity of breeding pairs is high and even in instances when pairs relocate nests, the distances involved are usually small (<30 m). Eggs are laid in a wide variety of natural crevices and holes, but most nest sites in the study area are located in cavities in rock masses. Eggs are usually laid about 50 cm from the entrance of the nest crevice, thus eggs, chicks, and attending adults are frequently accessible for data collection. Guillemots are unusual among alcids in that they normally lay two-egg clutches and raise two chicks per nesting attempt. Guillemots carry whole fish in their bills to the nest-site crevice to feed their young. Thus, individual prey items can be identified, weighed, measured, and, if necessary, collected for contaminant analyses.

As of 1994, results of damage assessment studies indicated that the pigeon guillemot population on Naked Island is continuing to decline. Naked Island is a major guillemot breeding colony site in PWS and has been the site of breeding biology studies since the late 1970s. The diet of guillemot nestlings on Naked Island has changed considerably from the pre-spill period, and growth rates of nestlings have declined. Nestling growth rates are currently lower than those on Jackpot Island, a colony in PWS that was not oiled.

Pigeon guillemots are a well-suited species for monitoring nearshore ecosystem health for several reasons:

• 1) they are a common and widespread seabird species breeding in coastal Alaska, and in PWS specifically;
• 2) they forage within 5 km of the nest site in the subtidal and nearshore zones;
• 3) unlike most seabird species, they do not breed in large, dense colonies;
• 4) they raise their young almost entirely on fish, preying primarily on nearshore demersal fish (e.g., blennies, sculpins) and on nearshore schooling fish (e.g., sandlance); and
• 5) the one- or two-chick broods are fed in the nest until the young reach adult body size."

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