The status and trends of Maine's island-nesting Herring Gull (Larus argentatus) and Great Blackbacked Gull (L. marinus) populations have changed dramatically over the last century. Aerial photographs were used to count nesting Herring and Great Black-backed gulls at all colonies along the coast of Maine, USA, in 2008 and 2013. Population trends were assessed by comparing current survey data to a previous coastwide survey in 1977. The breeding population of Herring Gulls in Maine was estimated at 24,302 pairs nesting on 180 islands during 2008 and 21,488 pairs nesting on 180 islands during 2013. This represents an annual decline of 2.3% in the number of nests in Maine from 2008 to 2013. The breeding population of Great Blackbacked Gulls in Maine was estimated at 10,094 pairs nesting on 197 islands during 2008 and 6,934 pairs nesting on 191 islands during 2013. This represents an annual decline of 6.3% in the number of nests in Maine from 2008 to 2013. Nesting populations for both species appeared to peak in the 1990s. Between 1977 and 2013, the number of Herring Gull nests in Maine declined by 17%, and the number of nesting islands declined by 19%. Great Black-backed Gull populations also declined between 1977 and 2013, with a 30% decline in the number of nests and a 14% decline in the number of islands supporting nesting. The reason for the decline is unknown, but we speculate that these declines may be related to changing food availability around colonies and increased predation rates by Bald Eagles (Haliaeetus leucocephalus) and mammals.
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Vol. 39 • No. sp1