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At least 1,207 records · Page 67Linked to original sources
USGS1979

Robust estimation from line transect data

Line transect sampling often provides a practical way to approach estimation of wildlife population density (Seber 1973, Eberhardt 1978). Burnham and Anderson (1976) provided a general framework for the estimation of animal density from line transect data, and many specific analytical methods have been proposed in the literature. Numerous persons are researching methods of statistical analysis for line transect data; however, little consideration has been given to specifying criteria for "good" methods of line transect estimation. We present here some criteria which we believe line transect estimators should satisfy. We do not deal with the case where objects may move from their initial location before being detected.

Journal of Wildlife Management↗
USGS1982

Breeding-ground habitat conditions and the survival of mallards

The relationship between habitat conditions in prairie breeding areas of North America and mallard ( Anas platyrhynchos ) survival rates was investigated. Annual survival-rate estimates for mallards generally were higher during years of high May pond numbers and low mallards-per-pond ratios than during years of low pond numbers and high ratios. This tendency was most pronounced among males. These results suggest that mallard survival probabilities may be affected by breeding-ground habitat conditions.

Journal of Wildlife Management↗
USGS1984

Current impact of DDE on black-crowned night-herons in the intermountain west

Organochlorine contamination was studied in eight black-crowned night-heron ( Nycticorax nycticorax ) populations nesting in Washington, Oregon, and Nevada in 1978-80. DDE was detected in 220 eggs sampled; eggshell thickness was negatively correlated with residues of DDE and polychlorinated biphenyls (PCB's). Other contaminants were detected in 35% or fewer of the eggs. Except for the two Columbia River colonies in which local DDE contamination was a probable compounding factor, a strong north-south clinal pattern of DDE residues among colonies existed. Southern colonies were most contaminated, and observed productivity was below population maintenance in one colony (Ruby Lake). At DDE levels in eggs above 8 ppm, clutch size and productivity decreased, and the incidence of cracked eggs increased. No evidence of breeding-ground DDE-DDT contamination was found except along the Columbia River.

Nevada, Oregon, Washington↗
USGS1984

Response of avian communities to herbicide-induced vegetation changes

The relationships between avian communities and herbicide modification of vegetation were analyzed on early-growth clear-cuts in western Oregon that had received phenoxy herbicide treatment 1 or 4 years previously. For both 1 and 4 years post-spray, vegetation development was greater in the third height interval (> 3.0 m) on untreated sites. All measures of vegetative diversity on untreated sites exceeded those on treated sites. Overall density and diversity of birds were similar between treated and untreated sites. Several bird species altered their foraging behavior on treated sites, i.e., birds using deciduous trees increased use of shrubs on treated sites. The primary effect of herbicide application was a reduction in the complexity of vegetation, a condition due primarity to the removal of deciduous trees. Small patches of deciduous trees scattered in clear-cuts treated with phenoxy herbicides can maintain an avian community similar to that on untreated sites.

Oregon↗
USGS1984

Geographic and temporal differences in band reporting rates for American black ducks

Recoveries of reward- and standard-banded American black ducks (Anas rubripes) were used to estimate band reporting rates and to investigate geographic and temporal variability in reporting rate for 1978-80. Reporting rates were higher close ( 20 km) to the parent banding site in 3 of 42 samples and were higher close to the nearest black duck banding site in 3 of 35 samples., Reporting rates were higher P 0.05) in Canada than in the Atlantic Flyway for the pre-huntIng season 1980-banded sample, but were otherwise similar among regions. Temporal differences over the duration of the study occurred, but there were no consistent trends over time. The small number of rejections suggests that there is little evidence of differences in band reporting rate by proximity to banding sites, geographic location, or over time. Thus, the best estimate of band reporting rate for black ducks is a constant 0.43. This estimate should be used with caution, because we believe that it overestimates reporting rate due to the unknown proportion of reward bands found that were not reported.

Journal of Wildlife Management↗
USGS1984

Midseason mapping of sunflowers using Landsat digital data

The mapping results suggest that for the midsummer Landsat data used, there was not a sufficiently reliable relationship between Landsat-derived spectral clusters and sunflowers to allow 'automated' production of useful sunflower location maps. The occurrence of sunflower pixels in all cluster classes was a consequence of the diversity in sunflower appearance at the point in the growing season when the Landsat image used for digital processing was acquired. -Authors

Journal of Wildlife Management↗
USGS1983

The relationship between harvest and survival rates of mallards: A straightforward approach with partitioned data sets

We randomly partitioned mallard ( Anas platyrhynchos ) bandings and recoveries from each of a number of selected reference areas into 2 groups and estimated survival and harvest rates for each area and group. This procedure produced independent vectors of survival- and harvest-rate estimates, which were used to test the general hypothesis that mallard survival and harvest rates were inversely related. We used Spearman rank correlation analysis and z-test contrasts between survival rates from years of high vs. low harvest rates. We also conducted computer simulation experiments to gain insight into the ability of these analyses to detect the relationship of interest. The data analyses suggested that survival and harvest rates of young females were inversely related, at least for the 5 areas included in the analysis. However, for young males and adults of both sexes, the analyses provided no evidence of an inverse relationship between survival and harvest rates, except possibly in a few specific areas.

Journal of Wildlife Management↗