Manawagonish Island is located along the north shore of the Bay of Fundy, approximately five km to the southeast of Saint John, New Brunswick. The 40 ha island is roughly one km in length and half a km in width, with the mainland shore being located only 1.5 km to the northwest. It is partially wooded with a foreshore that is covered by tides that range as high as eight metres. The shores are rock with coastal cliffs and many small inlets.
In 1987, a total of 2,095 pairs of Double-crested Cormorants were recorded on Manawagonish Island (about 2.3% of the Atlantic Coast population). More recent surveys have not been completed. In the early 1900s, populations of Double-crested Cormorants in the Maritimes were reduced to only a remnant through persistent persecution. In recent years, however, cormorant populations have increased and now there is believed to be over 100 colonies in the Maritimes. This colony of Double-crested Cormorants is among the three largest in the Maritimes.
Other species of colonial birds nesting on Manawagonish include Herring Gulls (over 800), and Great Black-backed Gulls (approximately 250). Glossy Ibis, a colonial nester with a breeding distribution largely restricted to the southern United States and the eastern seaboard south of Maine, attempted to nest on Manawagonish Island in 1986. This is the only known breeding attempt for this species in Canada.
In addition to the colonial nesters, Gadwall have been reported to nest on the island. Until the late 1930s, Gadwall were not known to breed in eastern North America. Their range has since been expanding, but they still occur in only small numbers in the Maritimes.
Conservation responses/actions for key biodiversity
Although many studies have shown that cormorants eat few fish of interest to people, shooting of Double-crested Cormorants, be it authorized or illegal, is still frequent. In comparison to more isolated breeding colonies, the Manawagonish Double-crested Cormorant colony is likely disturbed less often because of its proximity to Saint John. Pollution from industry and shipping, however, remains a potential threat.
Since 1992, The Nature Trust of New Brunswick, a non-governmental organization, has owned Manawagonish Island and has designated in a fully protected nature preserve.