Mallard Recruitment in the Agricultural Environment of North Dakota
Study Area
The study area was an area of 10,041 km2 in central North Dakota (99�.0'-100�.5'W long. and 47�.0'-47�.5'N lat.) (Fig. 1). It included portions of the Missouri Coteau and Drift Plain biogeographic provinces (Stewart 1975) in about equal proportions. The Missouri Coteau, composed primarily of rolling stagnation moraine and outwash plains, contained 14.6 ha/km2 of wetland. The Drift Plain an area of glacial drift with much less relief than the Coteau, contained 6.3 ha/km2 of wetland (Cowardin et al. 1981). The primary land use was for the production of small grains, sunflowers, hay, and pasture for beef cattle. Most of the pasture was native mixed-grass prairie. In recent years there has been a continuing trend in land use away from pastureland and toward cropland.
Annual rainfall averages 44.3 cm/year. Mean minimum temperature is 2.8 C and mean maximum is 11.1 C. The growing season is 119 days (Seago et al. 1970). Climatic fluctuation, especially in rainfall, is great and is reflected by the number of ponds available to waterfowl during the breeding season. Our study included 2 dry years, 1977 and 1980, and 2 wet years 1978 and 1979 (Table 1).
| Year | Departure from mean temperaturea Apr-Jun (Degrees C) | Departure from mean precipitationa Apr-Jun (cm) | Ponds/km2 Junb |
| 1977 | 4.4 | -2.26 | 1.06 |
| 1978 | 1.4 | 0.56 | 4.13 |
| 1979 | -1.8 | -0.25 | 7.19 |
| 1980 | 3.3 | -2.21 | 2.40 |
| aMonthly
temperature and precipitation data obtained from Jamestown, North Dakota,
situated 17 km east of the southeast corner of the study area. bObtained from aerial photography of 66 3.22-km2 plots. |
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