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Large numbers of waterfowl, especially canvasback (Aythya valisineria), used Western Stump Lake as a staging area during most of October 1985. Selection of the lake as a conditioning site by this species likely is caused by extensive, shallow-water beds of sago pondweed (Potamogeton pectinatus) and lack of human disturbance. A brief limnological and historical account of the lake is provided.
A breeding bird census and plant survey was conducted on 180 samples of lightly, moderately, and heavily grazed and hayed native grasslands in North Dakota in 1974. The ten most important cover plants on each of eight major physiographic landforms in three of the four regions (the Agassiz Lake Plain excluded) overlapped so extensively that only 19 species were involved: 13 grasses or sedges, four forbs, one shrub, and one clubmoss. Bird densities were generally highest in (i) regions and landforms containing numerous natural basin wetlands, (ii) flatter, glaciated landforms containing more fertile soils, and (iii) landforms of greater relief and high habitat heterogeneity. Avian species richness tended to decrease with increased grazing intensity, but total bird density increased due to higher populations of a few species, and hayland that had been mowed and raked during the previous growing season was highly attractive to some species.
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The aquatic Coleoptera of a prairie wetland complex in Stutsman County, North Dakota, were collected from April 1979 to November 1980. Identification of 2594 individuals confirmed 57 species, including seven new records for North Dakota. Two seasonally flooded and two semipermanent wetlands, totaling 7.43 ha, contained 53% of the Dytiscidae, 43% of the Haliplidae, 38% of the Hydrophilidae, and 22% of the Gyrinidae species previously identified from North Dakota. Although 49.1% of the Coleoptera species occurred in both types of wetlands, the occurrence of 29 species varied by wetland class.
Schroeder (1984) proposed a habitat suitability model for breeding canvasbacks (Aythya valisineria) based on the size, water regime, and emergent vegetation of wetlands. We evaluated the model with data from surveys of canvasbacks on 2265 wetlands in North Dakota, South Dakota, and Minnesota. The model proved inadequate as a predictor of canvasback pair density; the correlation between values produced by the model and canvasback pair densities was r = 0.0023 (P = 0.911). There were, however, suggestions of (1) higher canvasback density and frequency of occurrence on wetlands with more open interiors, and (2) a relation between canvasback density and wetland size that varied according to wetland permanence. We recommend that the model be improved by testing these relations, and possibly by incorporating determinants of water quality or pondweed (Potamogeton spp.) occurrence.
Abstract has not been submitted
Abstract has not been submitted
Abstract has not been submitted