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Geology topics

Douglas H. Johnson

Publications and source records attributed to Douglas H. Johnson.

At least 235 records · Page 13Linked to original sources
USGS1989

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) activity were positively correlated, as were activity indices of coyote (Canis latrans), Franklin's ground squirrel (Spermophilus franklinii), and black-billed magpie (Pica pica). Indices of fox and coyote activity were strongly negatively correlated (r = -0.51), as were those of badger (Taxidea taxus) and skunk (r = -0.46). Nest predation rates in the early part of the breeding season were positively related to indices of fox, American crow (Corvus brachyrhynchos), and badger activity. Predation rates in the latter part of the season were positively related to indices of fox and skunk activity. Predation rates on early-season nests were lower in areas and years in which larger fractions of seasonal wetlands contained water. For late-season nests, a similar relationship held involving semipermanent wetlands. We suspect that the wetland measures, which reflect precipitation during some previous period, also indicate vegetation growth and the abundance of buffer prey, factors that may influence nest predation rates.

Canadian Journal of Zoology↗
USGS1989

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 population size, and evaluates them by a subsampling experiment on waterfowl surveys. EB estimates, especially a simple limited—translation version, were more accurate and provided shorter confidence intervals with greater coverage probabilities than customary estimates.

Ecology↗
USGS1989

Least squares estimation of avian molt rates

A straightforward least squares method of estimating the rate at which birds molt feathers is presented, suitable for birds captured more than once during the period of molt. The date of molt onset can also be estimated. The method is applied to male and female mourning doves.

Biometrics↗
USGS1989

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 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.

Prairie Naturalist↗
USGS1988

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 migrant species from a global pool, 33 migrant species from a Western Hemisphere pool, and 13 species that migrated though North Dakota. The observed flocks formed randomly from the available species that used the North Dakota migration corridor but the North Dakota species were not a random selection from the Western Hemisphere and global pools of Arctic-nesting scolopacid sandpipers. In short, the ephemeral, mixed-species foraging flocks that we observed in North Dakota were random mixes from a nonrandom pool. The size-ratio distributions were consistent with the interpretation that use of this migration corridor by sandpipers has been influenced by some form of sizerelated selection such as competition

North Dakota↗
USGS1988

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 each habitat proportional to the number of nest initiations. The distribution of nest initiations was derived from estimates of breeding populations, preferences of species for nesting habitats, and availability of habitats. Nest success rates ranged from < 5 to 36% among regions, periods, and species. Rates were lowest in western Minnesota (MNW) and eastern North Dakota (NDE), intermediate in central North Dakota (NDC) and eastern South Dakota (SDE), and highest in central South Dakota (SDC). In regions with comparable data, no consistent trend in nest success was apparent from early to late periods. Gadwalls and blue-winged teal nested more successfully than mallards and pintails; the relative success of shovelers varied regionally. Ducks nesting in idle grassland were the most successful and those nesting in cropland were least successful. Mammalian predation was the major cause of nesting failure (54-85%) in all habitats, but farming operations resulted in 37 and 27% of the nesting failures in cropland and hayland, respectively. Most of the populations studied were not self-sustaining.

Minnesota, North Dakota, South Dakota↗
USGS1988

Applications of a simulation model to decisions in mallard management

A system comprising simulation models and data bases for habitat availability and nest success rates was used to predict results from a mallard (Anas platyrhynchos) management plan and to compare six management methods with a control. Individual treatments in the applications included land purchase for waterfowl production, wetland easement purchase, lease of uplands for waterfowl management, cropland retirement, use of no-till winter wheat, delayed cutting of alfalfa, installation of nest baskets, nesting island construction, and use of predator-resistant fencing.The simulations predicted that implementation of the management plan would increase recruits by 24%. Nest baskets were the most effective treatment, accounting for 20.4% of the recruits. No-till winter wheat was the second most effective, accounting for 5.9% of the recruits. Wetland loss due to drainage would cause an 11% loss of breeding population in 10 years.The models were modified to account for migrational homing. The modification indicated that migrational homing would enhance the effects of management. Nest success rates were critical contributions to individual management methods. The most effective treatments, such as nest baskets, had high success rates and affected a large portion of the breeding population.Economic analyses indicated that nest baskets would be the most economical of the three techniques tested. The applications indicated that the system is a useful tool to aid management decisions, but data are scarce for several important variables. Basic research will be required to adequately model the effect of migrational homing and density dependence on production. The comprehensive nature of predictions desired by managers will also require that production models like the one described here be extended to encompass the entire annual cycle of waterfowl.

Fish and Wildlife Technical Report↗
USGS1988

Determinants of breeding distributions of ducks

The settling of breeding habitat by migratory waterfowl is a topic of both theoretical and practical interest. We use the results of surveys conducted annually during 1955-81 in major breeding areas to examine the factors that affect the distributions of 10 common North American duck species. Three patterns of settling are described: homing, opportunistic, and flexible. Homing is generally more pronounced among species that use more stable (more predictable) wetlands, such as the redhead (Aythya americana), canvasback (A. valisineria), lesser scaup (A. affinis), mallard (Anas platyrhynchos), gadwall (Anas strepera), and northern shoveler (Anas clypeata). Opportunistic settling is more prevalent among species that use less stable (less predictable) wetlands, such as northern pintail (Anas acuta) and blue-winged teal (Anas discors). Flexible settling is exhibited to various degrees by most species.The 10 species are shown to fall along a natural ordination reflecting different life history characteristics. Average values of indices of r- and K-selection indicated that pintail, mallard, blue-winged teal, and shoveler have the most features associated with unstable or unpredictable environments. Gadwall, American wigeon (Anas americana), and green-winged teal (Anas crecca) were intermediate, and attributes of the diving ducks were associated with the use of stable or predictable environments.Some species--notably mallard, gadwall, blue-winged teal, redhead, and canvasback--tend to fill available breeding habitat first in the central portions of their range, and secondly in peripheral areas. Other species--American wigeon, green-winged teal, northern shoveler, northern pintail, and lesser scaup--fill their habitat in the order it is encountered during spring migration.Age and sex classes within species vary in their settling pattern. Some of this variation can be predicted from the mating systems of ducks in which breeding females, especially successful ones, have a greater investment in habitat resources and are more likely to return to the same area in subsequent years.

Wildlife Monographs↗
USGS1988

Some considerations in modeling the mallard life cycle

We outline a population model proposed to accommodate the full life cycle of the mallard (Anas platyrhynchos}. Events during the breeding season are better understood than events at other times of the year, but recent findings suggest the importance of phenomena away from the breeding grounds. Several processes are discussed relative to mallard population dynamics. Compensatory mortality is a poorly understood concept, but one that can overwhelm many other components of a population model. Diseases and environmental contaminants can inflict indirect as well as direct mortality and can reduce reproduction. They interact with numerous other variables in complex and yet unknown ways. Recent evidence of a wintering-ground effect on subsequent recruitment provides one avenue for modeling phenomena occurring at different times of the year. Finally, the role of heterogeneity among individuals is widely acknowledged but not fully appreciated. We illustrate with an example the importance of heterogenicity to population processes, including compensatory mortality.

Book chapter↗
USGS1988

Some considerations in modeling the mallard life cycle

We outline a population model proposed to accommodate the full life cycle of the mallard (Anas platyrhynchos). Events during the breeding season are better understood than events at other times of the year, but recent findings suggest the importance of phenomena away from the breeding grounds. Several processes are discussed relative to mallard population dynamics. Compensatory mortality is a poorly understood concept, but one that can overwhelm many other components of a population model. Diseases and environmental contaminants can inflict indirect as well as direct mortality and can reduce reproduction. They interact with numerous other variables in complex and yet unknown ways. Recent evidence of a wintering-ground effect on subsequent recruitment provides one avenue for modeling phenomena occurring at different times of the year. Finally, the role of heterogeneity among individuals is widely acknowledged but not fully appreciated. We illustrate with an example the importance of heterogeneity to population processes, including compensatory mortality.

Book chapter↗
USGS1987

A model of the productivity of the mallard duck

This paper describes a stochastic computer model that simulates recruitment of the mallard ( Anas platyrhynchos ) under different habitat conditions and management scenarios. The model incorporates several environmental phenomena and biological relations that affect mallard recruitment. Major events include arrival of mallards in the spring, daily survival of hens, initiation of nests, selection of nest sites, survival of nests until hatching, and survival of broods until fledging. The model was originally developed as a tool for synthesizing the results of research. Subsequently, we applied the model to a variety of management situations. We also describe the sources of estimates used in the model, evaluate its sensitivity to input parameters, and review some practical applications.

Ecological Modelling↗