Southwestern Saskatchewan, Saskatchewan
Lake Diefenbaker is situated in southcentral Saskatchewan. The lake is actually a flooded portion of the South Saskatchewan River, created by the construction of the Gardiner Dam in the late 1950s. It is a very large artificial lake that extends over 100 km in length, and varies from one to three km in width. The eastern portion of the lake begins just west of the town of Riverhurst, and extends to the Elbow, including Gordon McKenzie Arm and Thomson Arm. Although less rugged than the western portion of the lake, the eroded banks and associated slopes are steep and rough. Shores along the eastern portion of the lake support one of the largest populations of Piping Plovers in Saskatchewan. While large portions of the surrounding plateaus have been cultivated, there are still vast expanses of native prairie, much of which is used for grazing. Steep wooded coulees along the numerous creeks that flow into the lake provide ample habitat for woodland bird species.
In 1991, Lake Diefenbaker supported the largest population of nesting Piping Plovers in North America. (Piping Plovers are designated as globally vulnerable and nationally endangered.) As many as 227 Piping Plovers have been recorded during a single year, and over an 11-year period (1984 1995) a total of five surveys yielded an average of 92 breeding pairs. In 1996, only 28 pairs (75 birds in total) were recorded (the lower numbers are likely related to high water levels). On average, east Lake Diefenbaker supports as much as 3.5% of the worlds Piping Plover population, and as much as 13.5% of the Canadian prairie population. The eastern portion of Lake Diefenbaker is also important for staging ducks, with between 5,000 and 20,000 birds being recorded in 1990. The lake also attracts large numbers of staging shorebirds, and during the 1991 spring migration 300 Western Grebes were recorded.
Although large numbers of Piping Plovers nest on the eastern portion of Lake Diefenbaker, very rarely are these birds successful. Fluctuation of water levels from heavy rains, spring runoff, and water management strategies, often flood the Piping Plover beaches and destroy the nests and/or newly hatched fledglings. Trampling of the nesting beaches by cattle and use of all terrain vehicles also creates disturbance that often lowers productivity.
Most of Gordon McKenzie Arm (all but five short segments) and Thomson Arm (all but two shores and one long segment) are designated as critical Piping Plover habitat (used by one or more pairs of plovers with a reasonable expectation of repeat use). Under the provincial Wildlife Habitat Protection Act, this designation protects the shoreline to the high water mark from development. Two provincial parks are also located on this section of Lake Diefenbaker: Danielson Provincial Park at the north end of Thomson Arm, and Douglas Provincial Park at the southeast shore of Gordon McKenzie Arm.Catégories ZICO Habitats Usages Menaces Potencielles ou Existantes Status de Protection
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