Middle Lake, Saskatchewan
Basin and Middle Lakes are large saline parkland lakes located about 40 km north of Humboldt, Saskatchewan. The main water sources for these lakes are intermittent creeks that only carry water during spring runoff and periods of heavy rains. As such, these sites are subjected to severe water level fluctuations. Basin Lake, with an average depth of 9 m, has extensive rocky and sandy areas, as well as extensive mudflats along its shoreline. This lake is essentially devoid of emergent vegetation. Middle lake, with an average depth of 1 m, has a similar shoreline profile, but extensive wet meadow zones occur on the east and south shores. Much of Middle Lake is open water with extensive stands of cattail and bulrush in the shallow marshy bay in the southwest corner of the lake.
This site is important for waterfowl and shorebirds. During surveys completed in 1988 and 1989, an average of 9,578 shorebirds were recorded during three one-day surveys (5,830 May 25, 1988; 10,282 May 30, 1988; and 12,623 May 1989). Undoubtedly, thousands of additional shorebirds would be observed during long study periods. In addition to shorebirds, over 30,000 ducks have been recorded at this site during the summer moulting period (20,000 on Basin Lake, and 10,000 on Middle Lake).
Surveys of breeding colonial waterbirds have also been completed at this site with 227 American White Pelicans and 745 Double-crested Cormorants being recorded during the early 1990s. Piping Plovers (globally vulnerable and nationally endangered) also nest at the lake in small numbers. During the 1996 International Piping Plover Census, two pairs were observed.
Other birds known or believed to breed on these lakes include several grebe species (Pied-billed, Horned, Eared, Western and Red-necked) along with California Gulls, Black Terns, Common Terns, and Black-crowned Night Herons.
These lakes are severely affected by drought. While this may benefit some birds (such as shorebirds), others, like ducks, pelicans, and grebes are adversely affected during such periods. As well, due to the high concentrations of waterfowl, botulism outbreaks could be a major threat to the health of thousands of birds. Basin and Middle Lake were identified as Migratory Bird Sanctuaries in 1925. More recently, one polygon on the east side of Basin Lake, and the east, north, and part of the west shorelines (except the south arm) of Middle Lake were designated as critical Piping Plover habitat, and are protected under the provincial Wildlife Habitat Protection Act.Catégories ZICO Habitats Usages Menaces Potencielles ou Existantes Status de Protection