Machias Seal Island is located in the Gulf of Maine, 25 km southwest of Grand Manan Island. It is an isolated islet of shattered and wave-washed rock, with a small area of grass and forbs overlaying gravelly soils. The tidal range is about 3 to 4m. A lighthouse, two houses and several sheds are the sole buildings on the island. The climate is cool and frequently windy and foggy.
Machias Seal Island is considered to be the most important seabird colony in the Bay of Fundy. The site supports the only regularly occurring colonies of Arctic Terns, and Atlantic Puffin in New Brunswick, and supports the largest colonies of these species in the Maritimes. Indeed, the Arctic Tern colony may be the largest in North America. Recent surveys (1996 and 1998) recorded an average of 1,964 pairs of Arctic Tern (an estimate for the entire North American population is unavailable). Large numbers of Common Terns are also present with the 1996 and 1998 surveys recording an average of 795 pairs (almost 2% of the estimated North American population). In 1998, about 3,500 pairs of Atlantic Puffins, and 700 pairs of Razorbills (about 1.9% of the estimated North American population) also nested on Machias Seal Island.
Roseate Terns (nationally endangered) occur regularly at Machias Seal Island, although nesting is not confirmed every year. The number of nesting pairs is seldom greater than one or two pairs, but even such a small number is significant since the national population of Roseate Terns is estimated to be only 87 to 137 pairs.
Other seabirds are found on Machias Seal Island in small numbers. A small colony of Leachs Storm Petrels (over 100 pairs) can be found in the north and northeastern parts of the island, and a Common Eider colony is also present with as many as 121 nests being recorded in 1998. There is some evidence to suggest that Common Murres have nested, and Laughing Gulls have been present during the breeding season but nesting is not yet confirmed. In addition to the species already mentioned, over seventy other species of songbirds, raptors and waterbirds were recorded during the 1998 field season.
Small numbers of the nationally endangered Harlequin Duck (eastern population) winter around the island, and are also present during the spring (16 were recently observed in mid-May). During the winter, large concentrations of Purple Sandpipers are also present.
BirdLife International (2020) Important Bird Areas factsheet: Machias Seal Island. Downloaded from http://www.birdlife.org on 07/07/2020.