Spring and early summer distribution of scoters and eiders in the St. Lawrence River estuary

The spring and summer distributions of scoters and eiders within the St. Lawrence estuary were studied with a combination of aerial and ground surveys. Aerial surveys were designed especially for scoters; they were flown higher (150 m) and covered a wider area (unlimited distance) than conventional waterfowl surveys. These surveys yielded nearly 10 times as many scoters as did conventional surveys. Approximately 40 000 scoters (the largest number observed in the aerial surveys) were counted in the study area on 9 May 1995. By 23 May, most scoters had departed for their breeding areas. In early May, scoters were most numerous along the north shore of the eastern portion of the St. Lawrence River estuary, and few birds used the south shore. Ground surveys suggest that most male scoters were back in the estuary by the end of June. During wing moult, the distribution of scoters was more clumped than in spring; as well, the south shore was more heavily used, and several sectors were avoided. Both Surf Scoters Melanitta perspicillata and Black Scoters M nigra are abundant in spring, but the summer scoter population is composed mostly of Surf Scoters. Important staging areas include the underwater plateaus around Ile Patte de Lievre, where birds also moult, and a few areas east of Forestville. In the spring, scoters also concentrate south of Ile aux Fraises, a well-known spawning site for Atlantic herring Clupea harengus. During the moult, scoters were seen east of Ile du Chafaud aux Basques, east of Ile Patte de Lievre, and at Ilets Jeremie and Papinachois on the north shore; and at L'Anse au Sable, Archipel des Rasades, and Saint-Andre-de Kamouraska on the south shore.