Factors Limiting Mallard Brood Survival
in Prairie Pothole Landscapes
Study Areas
We monitored radio-equipped female mallards and their broods on 7 51-km² circular plots located in 3 glacial landforms in the PPR (Table 1). Study areas 1 and 2 were located in dead-ice moraine in the Missouri Coteau near Kulm in south-central North Dakota (1988-91, 1993-94), and study areas 3 and 4 were on the glaciated drift plain near Jamestown in eastern North Dakota (1988, 1990-92, 1994; Bluemle 1977); study areas 5-7 were in terminal and ground moraine in west-central Minnesota near Detroit Lakes (1988-91; Leverett 1932).
| Table 1. Characteristics of 7 51-km² study areas located in eastern North Dakota (ND; MC = Missouri Coteau, DP = Drift Plain) and west-central Minnesota (MN) where radio-equipped mallard broods were monitored during late spring and summer 1988-94. Percentages of study areas in cropland, grassland, and wetland are based on status in May 1988. Number and area of wetland basins on each study area are listed by basin class. Number of radiomarked females hatching broods and number of broods experiencing total loss are identified for each study area. | |||||||||||||
| Study areaa | Habitat class (%) | No. wetland basins by classb | Basin area (ha) by class | Radiomarked females (n) |
Total brood loss (n) |
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| Crop | Grass | Wet | T | S | SP | L | T | S | SP | L | |||
| ND-MC | |||||||||||||
| 1 | 34 | 34 | 19 | 531 | 689 | 130 | 2 | 98 | 275 | 562 | 17 | 22 | 4 |
| 2 | 55 | 17 | 13 | 169 | 203 | 111 | 2 | 116 | 181 | 337 | 18 | 1 | 1 |
| ND-DP | |||||||||||||
| 3 | 64 | 5 | 13 | 513 | 371 | 35 | 1 | 115 | 201 | 339 | 1 | 22 | 4 |
| 4 | 58 | 10 | 18 | 768 | 258 | 99 | 1 | 149 | 170 | 463 | 123 | 1 | 0 |
| MN | |||||||||||||
| 5 | 62 | 5 | 17 | 270 | 292 | 133 | 9 | 55 | 110 | 272 | 451 | 2 | 2 |
| 6 | 64 | 5 | 11 | 205 | 321 | 137 | 31 | 64 | 225 | 190 | 252 | 1 | 0 |
| 7 | 49 | 10 | 14 | 218 | 315 | 156 | 38 | 45 | 78 | 207 | 354 | 7 | 5 |
| a Study area locations: 1
(46°27'N, 98°56'W; 2 (46°11'N, 98°53'W); 3 (47°11'N,
98°40'W); 4 (46°43'N, 98°06'W); 5 (46°59'N, 96°12'W);
6 (46°55'N, 96°02'W); 7 (46°51'N, 96°13'W). b Wetland basin classes: temporary (T), seasonal (S), semipermanent (SP), and lake (L) after Cowardin et al. (1988). Class of each wetland basin was obtained from digitized maps of study areas prepared by the U.S. Fish and Wildlife Service National Wetland Inventory (NWI) with wetland classification based on water regime (Cowardin et al. 1979). Basin class is named after the most permanent water regime present within the basin and neither class nor area changed among years. |
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Most land in the study areas was privately owned; public land was limited primarily to scattered Waterfowl Production Areas (WPAs) owned and managed by the U.S. Fish and Wildlife Service. Uplands on study areas were used largely for production of cereal grains, row crops, hay, and livestock grazing. Proportions of landscapes in cropland and grassland varied widely among sites (Table 1). Wetland basins included temporary, seasonal, semipermanent, and lake classes (Cowardin et al. 1988), which are nearly equivalent to classes II--V of Stewart and Kantrud (1971). Number and area of wetland basins varied among study areas, both within and among classes (Table 1).
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