At-sea observations of ivory gulls (Pagophila eburnea) in the eastern Canadian high Arctic in 1993 and 2002 indicate a population decline

摘要

Evidence from colony surveys and local Inuit knowledge strongly suggest that the Canadian population of ivory gulls (Pagophila eburnea) has declined dramatically. The observations of ivory gulls at sea presented here are consistent with this. Ivory gulls were observed during two cruises on the Russian icebreaker Kapitan Khlebnikov in the eastern Canadian high Arctic in August 1993 and 2002. Ivory gulls were seen 3.5 times more often in 1993 (n = 176) than in 2002 (n = 149), and, corrected for observation effort, four times more ivory gulls were seen in 1993 than in 2002. Ivory gulls are scavengers: they were never observed feeding on fish behind the vessel while ice-breaking, although black-legged kittiwakes (Rissa tridactyla) often were seen feeding in this way. Ivory gulls were observed scavenging around polar-bear (Ursus maritimus) kills in 1993 but not in 2002. By far the largest number of ivory gulls was seen near Grise Fiord in 1993. There, opportunities for them to scavenge were likely good at the community landfill as well as at Inuit and polar-bear kills due to complete ice coverage of the surrounding marine area. No ivory gulls were seen there in 2002. Observations of four individuals in 1993 and five individuals in 2002 near the southern end of Eureka Sound and in Norwegian Bay, 150 km from the nearest known breeding colonies, suggest that as yet undiscovered colonies might exist in this area. With three lines of evidence (colony surveys, local Inuit knowledge, at-sea surveys) now indicating population decline, urgent reassessment of the status of ivory gulls in Canada needs to take place.