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Endangered Species and Spaces

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4.11 Western Grebe: Aechmophorus occidentalis
     
(Lawrence)

      Order: Podicipediformes
      Family: Podicipedidae

Status

Global Rank: G5
Provincial Rank: S1B, S3N
COSEWIC: not addressed

Provincial Listing: Red list

Distinguishing Features

Grebes are "tailless" water birds that are excellent swimmers and divers. They have lobed toes; not fully webbed ones. As in loons, their legs are attached far back on their body, so they move awkwardly on land. The Western Grebe is a large grebe, with a long slender neck, sharply contrasting black and white colouration and red eyes. The bill is slender, sharp and slightly up-tilted and greenish-yellow in colour (Godfrey, 1986).

Distribution

Columbia Basin: One of only three regular breeding locations in B.C. is located at Duck Lake near Creston (Creston Valley Wildlife Management Area).

British Columbia: Regular breeding populations are restricted to Salmon Arm, the north arm of Okanagan Lake, and Duck Lake near Creston. Winter populations are widely distributed along the coast and sparsely and locally distributed on large, open bodies of water in the interior. Formerly bred at Williams Lake, and Swan Lake near Vernon. A colony at Kamloops Lake was used only in 1973 and a pair bred at Westham Island in 1986 (Cannings et al. In prep.).

Global: Breeds from sc. British Columbia, c. Alberta, c. Saskatchewan and sw. Manitoba south to New Mexico, Nebraska, Iowa and Minnesota. Winters along Pacific coast, more uncommonly inland, from s. British Columbia south to c. Mexico (Cannings et al. In prep.).

Habitat

Nesting habitat includes emergent vegetation along the margin of medium to large lakes although they occasionally nest on floating vegetation in the open. Nests consist of large masses of vegetation over bases constructed of decaying bulrush, cattail, or reed canary grass. Other attributes essential to good nesting habitat are a long ice-free period with stable water levels, access to open water that is deep enough to allow substantial fish populations, protection from wind and waves, and minimal human disturbance. Small numbers of grebes winter in the interior in large lakes and sloughs, and slow-moving rivers (Cannings et al. In prep.).

Threats

Widely distributed and globally secure. However, breeding population in B.C. may be fewer than 200 pairs. Breeding populations are declining, with five historically used sites now reduced to three. Human disturbance (primarily wave-wash from powerboats) directly threatens nesting sites through increased annual reproductive losses and/or colony abandonment. An expanding colony of Ring-Billed Gulls may be a threat to the colony at Shuswap Lake. Large aggregations of wintering grebes are vulnerable to oil spills (Cannings et al. In prep.).

Biology

Western Grebes feed mainly on fish (80 - 100% of the diet), but crustaceans, worms, and insects are occasionally taken. Spring migration is generally from late April to early May with most birds having left the coast by mid-May. Autumn migration is greatest from mid-September to mid-October. Brood size varies from 1 to 4 in British Columbia, and hatching occurs mainly from late June to early July (Cannings et al. In prep.).

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