Background: This study looks at the value of inland wetlands to avifauna in winter. The three lakes on the Applegate Ranger District (Applegate Lake, Upper & Lower Squaw Lakes) are currently being surveyed until March for wintering waterfowl. The questions I wanted to answer were: What factors will effect the distribution and density of populations of waterfowl at each of the lakes? They each differ in terms of their naturalness, remoteness, size, depth, amount of human disturbance and elevation. Applegate Lake and Lower Squaw Lake are unnatural with the water level being artificially controlled throughout the seasons. The maturity of the lakes is another factor that may affect wintering waterfowl. Applegate Lake was created less than 20 years ago while Squaw Lakes are post-glacial features, estimated to be around half a million years old. Plant and animal communities have been able to develop more naturally in Squaw Lakes than in Applegate Lake. Motorized boats are permitted on Applegate Lake but not on Squaw Lakes. Is size important? Does the close proximity of the Squaw Lakes give a non-representative value of the birds they support? How important is elevation. On Upper Squaw Lake large areas are frozen for most of the day. Do birds use Lower Squaw Lake in the morning and then migrate to new foraging grounds when the ice melts?
Findings: So far a total of 16 species of waterfowl (ducks, geese, grebes, coots and shorebirds) have been seen along with 31 non-waterfowl species, mainly passerines (perching birds) and a few non-passerines (grouse, quail etc.) on the three lakes. Individually, Applegate Lake was found to contain the highest species diversity, 40 species in total compared to 22 species at Lower Squaw Lake and 18 at Upper Squaw Lake. There is little difference between the numbers of waterfowl species at the three lakes. Species diversity increased with size of the lake. Applegate Lake was the highest with 12 species followed by Lower Squaw Lake (11 species) and Upper Squaw Lake (10 species). The trend for non-waterfowl species followed along the same lines although the 28 non-waterfowl species seen at Applegate Lake was much higher than at either of the other lakes.
Species richness (densities of each species) was noticeably higher at Applegate Lake. A total of 467 birds were seen (mainly common mergansers, geese, chickadees, kinglets and juncos) at Applegate Lake compared to 158 at Upper Squaw Lake (high numbers of mallards) and 113 at Lower Squaw Lake (the majority being mallards and coots). The number of "unique species" at each of the three lakes was also calculated. "Unique species" are only found at one site and have been recorded on at least two visits (to avoid accidentals). In terms of the waterfowl species, Applegate Lake and Upper Squaw Lake had one each, spotted sandpiper and the American coot respectively. It is worth mentioning that while Lower Squaw Lake did not have any unique species of waterfowl, it did have higher numbers of certain species than the other lakes, pied-billed grebe being one example. Applegate Lake was the only site to have any unique species of land birds, 11 in total. It suggests that it is caused by the larger area and wider variety of habitats around the lake compared to the others.
Applegate Lake is over 600 meters deep in places and attracts diving waterfowl species such as the common merganser. Squaw Lakes being shallower are inhabited by dabbling or surface feeding duck species such as American wigeon. The artificially created low water level in Applegate Lake, forms mud-flats that attract shorebirds such as the spotted sandpiper. The closeness of the two Squaw Lakes gives more importance to their relative small size. This means their values are enhanced by an increased area of size and therefore the ability to hold more birds. Birds have been seen to frequent both lakes.