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Site description (2001 baseline)
The Havre aux Basques lagoon is located between the islands of Cap aux Meules and Havre-Aubert in the Magdalen Islands archipelago. These two islands, nearly 11km apart, are interconnected by two nearly parallel sand dunes. The southern section of the Havre aux Basques lagoon is characterized by open water, while the northern section is comprised of a network of canals surrounding sandy inlets, and salt meadow-marsh prairies. In 1956, the construction of a provincial road along the east side of the lagoon resulted in the closure of two of the three openings from the lagoon to the Gulf of St. Lawrence. Since the closure of these openings, there has been a noticeable increase in sand deposition and a reduction in the average tide level within the lagoon. The sand dune and associated beach along the west side of the lagoon is generally referred to as Plage de l’Ouest. Plages de la Martinique et de Havre-Aubert, on the east side have been identified as a separate IBA.

Key biodiversity
The Lagune du Havre aux Basques and Plage de l’Ouest support significant breeding populations of Piping Plovers and Common Terns, along with significant concentrations of shorebirds during fall migration.

Plage de l’Ouest is one of the principal breeding sites within the Magdalen islands for the nationally endangered and globally vulnerable Piping Plover. Well over 1% of the Canadian population of breeding plovers has consistently been recorded at the site from 1979 onwards. An average of 10 pairs bred here in the years between 1994 and 1998, with a peak of 14 pairs iin 1995. The average is equivalent to 5% of the Atlantic Canada population.

Common Terns make their nests on an island in the lagoon along with smaller numbers of Arctic Terns. The estimated Common Tern population in 1990 was 1510 birds, or about 1.5% of the estimated North American population. Two records of a pair of Roseate Terns nesting within the mixed tern colony were noted in 1982 and 1983. No accounts of this nationally endangered species have shown up in recent censuses. Another species of interest, the Common Black-headed Gull, has been recorded nesting in tern colonies in the northern part of the lagoon, which is one of the two known colonies for this European migrant in the Gulf of St. Lawrence. Since 1981 an estimated six pairs have made use of this site.

During the fall migration, the shallow marshes, sandy beaches and lagoons within this site provide an abundance of food and habitat for a large variety of shorebirds. Approximately 55% of the shorebirds migrating through the Gulf of St. Lawrence use Havre aux Basques Lagoon as a stopover site (in 1973 a seasonal total of 21,712 was recorded). On occasion very large numbers of Short-billed Dowitchers are recorded (7,619 birds in 1981, or more than 2% of the global population). Older records also list large numbers of White-rumped Sandpipers at the lagoon (6,000 in 1956). Large numbers of Whimbrels, Semipalmated and Least sandpipers, Greater Yellowlegs (700 in 1974), Red Knots, and Black-bellied Plovers (1,500 in 1974, or about 1% of their North American population) have also been recorded in the past. Lesser Yellowlegs, Hudsonian Godwits, and Semipalmated Plovers are frequent visitors, while Caspian Terns, American Black Ducks and have been observed on several occasions.

Occasionally, large numbers of Great Cormorants are seen (it breeds nearby), but this species is usually only seen flying by. Short-eared Owls bred in the marshes between 1987 (or earlier) and 1993, but have not been seen since.

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Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Lagune du Havre aux Basques et plage de l'Ouest (Canada). Downloaded from https://datazone.birdlife.org/site/factsheet/lagune-du-havre-aux-basques-et-plage-de-louest-iba-canada on 23/12/2024.