Douglas Johnson (Former Employee)
Science and Products
Filter Total Items: 318
An empirical Bayes approach to analyzing recurring animal surveys An empirical Bayes approach to analyzing recurring animal surveys
Recurring estimates of the size of animal populations are often required by biologists of wildlife managers. Because of cost or other constraints, estimates frequently lack the accuracy desired but cannot readily be improved by additional sampling. This report proposes a statistical method employing empirical Bayes (EB) estimators as alternatives to those customarily used to estimate...
Authors
Douglas H. Johnson
Breeding canvasbacks: a test of a habitat model Breeding canvasbacks: a test of a habitat model
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...
Authors
Douglas H. Johnson, M.C. Hammond, T. L. McDonald, C.L. Nustad
Breeding bird census: 1988 - Kentucky bluegrass prairie: mixed prairie I-V Breeding bird census: 1988 - Kentucky bluegrass prairie: mixed prairie I-V
Abstract has not been submitted
Authors
Douglas H. Johnson
Importance of individual species of predators on nesting success of ducks in the Canadian prairie pothole region Importance of individual species of predators on nesting success of ducks in the Canadian prairie pothole region
We followed 3094 upland nests of several species of ducks. Clutches in most nests were lost to predation. We related daily nest predation rates to indices of activity of eight egg-eating predators, precipitation during the nesting season, and measures of wetland conditions. Activity indices of red fox (Vulpes vulpes), striped skunk (Mephitis mephitis), and raccoon (Procyon lotor)...
Authors
Douglas H. Johnson, Alan B. Sargeant, Raymond J. Greenwood
Size differences in migrant sandpiper flocks: Ghosts in ephemeral guilds Size differences in migrant sandpiper flocks: Ghosts in ephemeral guilds
Scolopacid sandpipers were studied from 1980 until 1984 during spring migration in North Dakota. Common species foraging together in mixed-species flocks differed in bill length most often by 20 to 30 percent (ratios from 1.2:1 to 1.3:1). Observed flocks were compared to computer generated flocks drawn from three source pools of Arctic-nesting sandpipers. The source pools included 51...
Authors
J.L. Eldridge, Douglas H. Johnson
Duck nest success in the prairie pothole region Duck nest success in the prairie pothole region
We estimated nest success of mallard (Anas platyrhynchos), gadwall (A. strepera), blue-winged teal (A. discors), northern shoveler (A. clypeata), and northern pintail (A. acuta) for 5 regions in North Dakota, South Dakota, and Minnesota, for 1-3 periods between 1966 and 1984, and for 8 habitat classes. We obtained composite estimates of nest success for regions and periods by weighting...
Authors
Albert T. Klett, Terry L. Shaffer, Douglas H. Johnson
Science and Products
Filter Total Items: 318
An empirical Bayes approach to analyzing recurring animal surveys An empirical Bayes approach to analyzing recurring animal surveys
Recurring estimates of the size of animal populations are often required by biologists of wildlife managers. Because of cost or other constraints, estimates frequently lack the accuracy desired but cannot readily be improved by additional sampling. This report proposes a statistical method employing empirical Bayes (EB) estimators as alternatives to those customarily used to estimate...
Authors
Douglas H. Johnson
Breeding canvasbacks: a test of a habitat model Breeding canvasbacks: a test of a habitat model
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...
Authors
Douglas H. Johnson, M.C. Hammond, T. L. McDonald, C.L. Nustad
Breeding bird census: 1988 - Kentucky bluegrass prairie: mixed prairie I-V Breeding bird census: 1988 - Kentucky bluegrass prairie: mixed prairie I-V
Abstract has not been submitted
Authors
Douglas H. Johnson
Importance of individual species of predators on nesting success of ducks in the Canadian prairie pothole region Importance of individual species of predators on nesting success of ducks in the Canadian prairie pothole region
We followed 3094 upland nests of several species of ducks. Clutches in most nests were lost to predation. We related daily nest predation rates to indices of activity of eight egg-eating predators, precipitation during the nesting season, and measures of wetland conditions. Activity indices of red fox (Vulpes vulpes), striped skunk (Mephitis mephitis), and raccoon (Procyon lotor)...
Authors
Douglas H. Johnson, Alan B. Sargeant, Raymond J. Greenwood
Size differences in migrant sandpiper flocks: Ghosts in ephemeral guilds Size differences in migrant sandpiper flocks: Ghosts in ephemeral guilds
Scolopacid sandpipers were studied from 1980 until 1984 during spring migration in North Dakota. Common species foraging together in mixed-species flocks differed in bill length most often by 20 to 30 percent (ratios from 1.2:1 to 1.3:1). Observed flocks were compared to computer generated flocks drawn from three source pools of Arctic-nesting sandpipers. The source pools included 51...
Authors
J.L. Eldridge, Douglas H. Johnson
Duck nest success in the prairie pothole region Duck nest success in the prairie pothole region
We estimated nest success of mallard (Anas platyrhynchos), gadwall (A. strepera), blue-winged teal (A. discors), northern shoveler (A. clypeata), and northern pintail (A. acuta) for 5 regions in North Dakota, South Dakota, and Minnesota, for 1-3 periods between 1966 and 1984, and for 8 habitat classes. We obtained composite estimates of nest success for regions and periods by weighting...
Authors
Albert T. Klett, Terry L. Shaffer, Douglas H. Johnson