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Common Terns are found across much of Canada, and breed primarily on freshwater and marine islands from the subarctic to the United States. The abundance of Common Terns in Canada has most likely shown little overall change relative to about 1970, though the species has decreased in abundance in the Great Lakes area and has shown decreases over the last 20 years in parts of the prairies. Competition with gulls, disruptions in the abundance of prey, and disturbance from recreational boats all adversely affect Common Terns at some breeding locations. This species has been identified as a priority for conservation and/or stewardship in one or more Bird Conservation Region Strategies in Canada.
Common Terns breeding in the Great Lakes face increasing disturbance from recreational boat traffic, but benefit from active management of habitat and predators at their colonies. At Machias Seal Island, New Brunswick (once the largest tern colony in the Gulf of Maine), terns have suffered near complete reproductive failure since 2003, and have largely deserted the colony since 2006. This dramatic decline in breeding success and abundance was associated with a switch in the diet fed to chicks, from herring to lower quality diet items, and may also have been exacerbated by increased predation from Great Black-backed and Herring Gulls (Gaston et al. 2009).
Environment and Climate Change Canada and partners have developed Bird Conservation Region Strategies in each of Canada’s Bird Conservation Regions (BCRs). In these strategies, selected species are identified as priorities for one or more of the following reasons:
Select any of the sub-regions below to view the BCR strategy for additional details.
