CORRELATES OF THE DISTRIBUTION AND ABUNDANCE OF WINTERING GULLS IN MAINE

Gull aggregation sites in Maine were survived by volunteers 22 Feb.-19 Mar. 1985-1987 to study differences in foraging site preferences betw een Herring Gulls (Larus argentatus) and Great Black-backed Gulls (L. marinus). Proportionately more Great Black-backed Gulls occurred at hu man-made versus natural food sources and at sites with small total gul l populations. The proportion of Great Black-backed Gulls at sites dec reased as distance from coast increased. Numbers of Herring Gulls were positively correlated with an index of the size of the human-made foo d supply at foraging sites but numbers of Great Black-backed Gulls wer e not. These results suggest that Herring Gull populations may have in creased more rapidly than Great Black-backed Gull populations in the e astern U.S. over the last 60 yr because Herring Gulls have exploited h uman-produced food sources more readily than Great Black-backed Gulls. Results corroborate other evidence showing that Great Black-backed Gu lls are more strongly restricted to a coastal distribution than are He rring Gulls, though the reasons why this might be so are unknown.