Populations, productivity, and feeding habits of seabirds on St. Lawrence Island, Alaska: Final report

Abstract

A field camp was established at Kongkok Bay near the southwest cape of St. Lawrence Island and occupied continuously from 24 May to 2 September 1987. Permanent study plots were selected for both cliff and crevice-nesting species, and regular observations were made throughout the breeding season to document attendance patterns, breeding phenology, and success. Periodic collections of adults offshore and of chick meals in the colonies were used to determine the food habits of study species. Additional plots for population monitoring of murres and kittiwakes were established in colonies near Savoonga on the north side of the island, and counts were made there between 23 July and 1 August. Shore based work was supplemented with offshore studies of seabird foraging distribution from the USFWS vessel TIGLAX between 18 August and 3 September 1987. Populations of all study species in the Kongkok Bay area increased since the last study of seabirds there (murres 20, kittiwakes 87, Least Auklets 8, Crested Auklets 442). Pelagic Cormorants, Common Murres, and Thick-billed Murres exhibited average, or above average, breeding success at Kongkok in 1987. Black-legged Kittiwakes exhibited near-total reproductive failure. Crested and Least Auklets had high levels of breeding success after the effects of observer disturbance were taken into account. Predation by microtine rodents and foxes was a significant source of chick mortality on auklets. Feeding concentrations were found primarily north of Gambell in the Anadyr Strait or western Chirikof Basin. Kittiwakes were dispersed widely over the study area. Diets of all species studied were normal and, with the exception of kittiwakes, there was no evidence of problems in obtaining food. Current methods for assessing population changes in cliff-nesting species are considered adequate, but better techniques are needed for crevice-nesting auklets. Time-lapse photography offers the greatest potential for monitoring auklet numbers. A protocol is suggested for monitoring populations of murres, kittiwakes, and auklets at colonies in the Bering and Chukchi Seas. It calls for annual visits to selected colonies during two stages of the nesting cycle to assess numbers and breeding productivity. The breeding failure of Black-legged Kittiwakes on St. Lawrence Island in 1987 was part of a pervasive syndrome of failure in this species observed throughout the Bering Sea and Gulf of Alaska in recent years. The causes of recurrent, widespread breeding failure need to be identified if kittiwakes are to have a role in area-wide population monitoring during the period of Alaskan development by the oil and gas industry.