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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)
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.

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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