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At least 1,081 records · Page 60Linked to original sources
USGS1988

A field test for differences in condition among trapped and shot mallards

We tested predictions from the condition bias hypothesis (Weatherland and Greenwood 1981) regarding the effects of sampling methods of body weights of mallards ( Anas platyrhynchos ) at White River National Wildlife Refuge (WRNWR), Arkansas, during 24 November-8 December 1985. Body weights of 84 mallards caught with unbaited rocket nets in a natural wetland were used as experimental controls and compared to the body weights of 70 mallards captured with baited rocket nets, 86 mallards captured with baited swim-in traps, and 130 mallards killed by hunters. We found no differences (P > 0.27) in body weight among sampling methods, but body condition (wt/wing length) of the birds killed by hunters was less (P < 0.02) than that of the controls. Power of the test statistics to reject the null hypothesis of equal body weights among sampling methods was > 0.75 for differences > 50 g. The condition bias hypothesis probably applies to ducks killed by hunters but not to trapping operations when substantial (> 20 at 1 time) numbers of birds are captured.

Arkansas↗
USGS1988

Sublethal landrin toxicity: Behavioral and physiological effects on captive vultures

Use of conditioned taste aversion (CTA) has been proposed to reduce consumption of California condor (Gymnogyps californianus) eggs by ravens (Corvus corax). Although landrin has induced aversions in ravens and other birds, no data were available on behavioral and physiological effects of landrin on condors, non-target birds that might consume treated eggs. Because condors are endangered, we selected taxonomically related surrogates to approximate the effects on condors of acute oral doses of landrin. Seven black vultures (Coragyps atratus), 2 turkey vultures (Cathartes aura), and 2 king vultures (Sarcoramphus papa) received landrin and placebo treatments 1 week apart. Plasma cholinesterase (ChE) activity was monitored at zero, 3, and 24 hours posttreatment, and behavioral observations were made for 2 hours posttreatment. The doses tested were nonlethal, and ChE levels approached normal within 24 hours after treatment. Only the frequency of vomiting differed statistically between the placebo and landrin treatment. We conclude that with appropriate precautions, landrin can be used in applications of CTA to discourage consumption of condor eggs by ravens, while posing no apparent risk to reintroduced condors.

Journal of Wildlife Management↗
USGS1988

Environmental contaminants in California condors

Five wild California condors ( Gymnogyps californianus ) that died in 1980-86 were necropsied and tissues were analyzed for environmental contaminants. Three died of lead (Pb) poisoning, 1 presumably of cyanide (CN) poisoning, and 1 nestling of handling shock. Organochlorine concentrations were low in 4 condors that were analyzed for these contaminants. Blood samples from 14 wild and 14 captive condors were analyzed primarily for Pb. Five of 14 wild condors sampled had elevated (> 0.70 ppm) concentrations of Pb in blood whereas Pb concentrations in all captive condors were low. Lead levels in individual birds often fluctuated over time. Lead exposure, especially poisoning, was a major factor affecting the wild California condor population during 1982-86. The probable source of Pb was bullet fragments in carrion on which condors were feeding.

California↗
USGS1988

Nonhunting mortality in sandhill cranes

Records of 170 sandhill cranes ( Grus canadensis ) necropsied at the National Wildlife Health Research Center, Wisconsin, from 1976 through 1985 were reviewed as representative samples to determine causes of nonhunting mortality in the mid-continent and Rocky Mountain populations of sandhill cranes. Avian cholera, avian botulism, and ingestion of mycotoxins were leading causes of nonhunting mortality. Hailstorms, lightning, lead poisoning, predation, avian tuberculosis, and collisions with power lines also killed cranes.

Journal of Wildlife Management↗
USGS1988

Guild structure of a riparian avifauna relative to seasonal cattle grazing

The avifauna within the willow ( Salix spp.) community on the Arapaho National Wildlife Refuge (NWR) was dominated (96% of all observations each year) by 11 species of passerine birds during the summers of 1980-81. Using 28 vegetation variables measured or calculated for randomly selected points and points where birds were sighted, we assigned the species to 3 distinct response guilds relative to historical patterns of seasonal grazing. A eurytopic response guild (habitat generalists) included yellow warblers ( Dendroica petechia ) (YEWA), savannah sparrows ( Passerculus sandwichensis ) (SASP), and song sparrows ( Melospiza melodia ) (SOSP). A stenotopic response guild (habitat specialists) included willow flycatchers ( Empidonax traillii ) (WIFL). Lincoln's sparrows ( Melospiza lincolnii ) (LISP), and white-crowned sparrows ( Zonotrichia leucophrys ) (WCSP). The intermediate, mesotopic response guild included American robins ( Turdus migratorius ) (AMRO), red-winged blackbirds ( Agelaius phoeniceus ) (RWBL), and brown-headed cowbirds ( Molothrus ater ) (BHCO). Population densities of the eurytopic response guild differed little between healthy (historically winter-grazed) and decadent (historically summer-grazed) willow communities within a year. Densities of species in the mesotopic response guild differed more dramatically, and stenotopic response-guild species were absent or accidental in decadent willows. Information on habitat use patterns of the individual species between years supported the definition of response guilds; vegetation structure was most variable in habitats of eurytopic species and least variable in habitats of stenotopic species. Comparisons between used and available vegetation features indicated that species in the stenotopic response guild used locations that differed from random on the basis of bush spacing. We hypothesize that the response-guild structure primarily reflects the impact of cattle upon the horizontal patterning of the vegetative community.

Colorado↗
USGS1989

Survival analysis in telemetry studies: The staggered entry design

The estimation of survival distributions for radio-tagged animals is important to wildlife ecologists. Allowance must be made for animals being lost (or censored) due to radio failure, radio loss, or emigration of the animal from the study area. The Kaplan-Meier procedure (Kaplan and Meier 1958), widely used in medical studies subject to censoring, can be applied to this problem. We developed a simple modification of the Kaplan-Meier procedure that allows for new animals to be added after the study has begun. We present 2 examples using telemetry data collected from northern bobwhite quail ( Colinus virginianus ) to show the simplicity and utility of the Kaplan-Meier procedure and its modifications. The log rank test used to compare 2 survival distributions can also be modified to allow for additions during the study. Simple computer programs that can be run on a personal computer are available from the authors.

Journal of Wildlife Management↗
USGS1989

Body composition and weight dynamics of wintering greater white-fronted geese

Adult greater white-fronted geese ( Anser albifrons frontalis ) wintering in southern Oregon and California increased or maintained body weight in autumn, lost weight from autumn through winter, and rapidly increased in weight before spring migration in late April. We documented significant annual differences in body weights for both sexes. We related seasonal changes in body weight to changes in lipid levels, which were lowest (12-13% of wet wt in M and F) in mid-March and highest in late April (24% in F). Greater white-fronted geese maintained lipid levels during winter similar to those reported for large subspecies of Canada geese ( Branta canadensis ), and greater than those reported for small subspecies of Canada geese and other small species of geese. Protein content of carcasses varied significantly in females; i.e., lowest in early October and highest in late October and late April. Differences among species in patterns of weight change and body composition during winter seem to be related to social organization, body size, food type, and foraging behavior. Females left spring staging areas weighing relatively less than most other species of geese and may have benefited from foraging opportunities on the nesting grounds.

California, Oregon↗
USGS1989

Generalized procedures for testing hypotheses about survival or recovery rates

Comparisons of survival or recovery rates from different time periods or geographic regions may be difficult to accomplish using the Z-tests suggested by Brownie et al. (1985). We propose a general Chi-square statistic that addresses an unambiguous null hypothesis of homogeneity among several survival or recovery rates. With this statistic, specific hypotheses of differences in rates can be simultaneously tested using contrasts. If necessary, a posteriori multiple comparisons can also be conducted that incorporate an adjustment for Type I error.

Journal of Wildlife Management↗
USGS1984

Movements of translocated wolves in Minnesota

From Feb. 1975-May 1978, 104 wolves ( Canis lupus ) captured at or near Minnesota farms where depredations on livestock had been reported were translocated northward and eastward for 50-317 km into extensive forests; 3 others were released westward. Nine wolves were translocated twice, and 1 three times. Information on movements was obtained by radiotracking 17 wolves and by recovery of 16 others. All radio-tagged wolves left the release areas; adults left quickly, but pups generally remained longer, behaved less decisively, and settled nearby temporarily. Wolves released together did not remain together. Initial travel of most radio-tagged adults was between south and west, the general direction to their original location. Final directions were primarily to the west and northwest, due in part to physiographic barriers. Eight adults homed, 1 twice, to capture areas that were < 64 km from release sites. Nonhoming wolves were radiotracked and/or recovered 32-351 km from their capture sites and 23-302 km from their release sites. Translocation was largely unsuccessful at keeping problem wolves out of lifestock production areas. The problem of initial travel away from release sites in wolf reintroductions probably could be minimized by transport and release of 6-9 mo. old wolves.

Minnesota↗
USGS1984

Elk and deer diets in old-growth forests in western Washington

Dietary quality and overlap of sympatric Roosevelt elk ( Cervus elaphus roosevelti ) and Columbian black-tailed deer ( Odocoileus hemionus columbianus ) were investigated in old-growth forests of the Hoh Valley, Olympic National Park, Washington. Diets of both cervids were comprised mainly of common old-growth flora, particularly in winter. High dietary overlap suggested competitive interactions for food, especially in winter when forage resources were least available. Predominant forages in fall and winter diets seemed to afford little opportunity for cervids to select different plant parts. Crude protein (CP), in vitro dry matter digestibility (IVDMD), and phosphorus (P) in important forages varied with phenology, but seasonal trends were more pronounced for shrubs and grasses than forbs and trees. CP, IVDMD, and P in cervid diets also varied seasonally and usually in the following ascending order: winter, fall, summer, spring. CP and P appeared to be adequate in diets, but low IVDMD suggested that digestible energy was limited. Few significant differences in seasonal dietary qualities were demonstrated between elk and deer. The collective cervid population (and its habitat) in the Hoh Valley is unmanaged and probably at equilibrium with its food resource, or at ecological carrying capacity. Results are discussed in light of herbivore--habitat interactions at equilibrium densities.

Washington↗
USGS1984

Breeding biology of Pacific white-fronted geese

Nesting ecology of Pacific white-fronted geese ( Anser albifrons frontalis ) was studied on a 9.9-km 2 area on the Yukon-Kuskokwim (Y-K) Delta, Alaska, during 1977-79. Availability of nesting habitat varied considerably among years because of differences in time of snow- and icemelt. Mean clutch size was 3.7 eggs in the late spring thaw year and 5.2 and 5.7 eggs in early snowmelt years. Peak (and duration) of nest initiation was 1-2 June (16 days) in the late spring and 15-18 May (20-21 days) during early springs. When nest sites were available early, the time interval between arrival and date of nest initiation closely approximated the time required for rapid yolk development. This suggests that whitefronts may be physiologically prevented from nesting earlier in such years. The duration of nest initiation was comparable to that of other goose species nesting on the Y-K Delta, but longer than for goose populations of several species nesting farther north or in the midcontinent. Overall, 68% of whitefront nests were in lowland habitat, 23% in intermediate habitat, and 10% in upland habitat, but habitat use varied significantly between early and late years. Whitefronts most commonly nested on slough banks (55%), lake shores (23%), and grass-sedge meadows (11%). A quantitative description of vegetation associated with nest sites is given. Major causes of nest destruction were flooding (28%) and predation (9%). Nesting success over the 3-year period averaged 62%.

Alaska↗
USGS1984

Organochlorine contaminants in California waterfowl

Concern has been expressed that the extensive use of organochlorine pesticides in California may be exposing waterfowl to hazardous contaminant levels. The objectives of our study were to: (1) determine concentrations of organochlorines in northern pintails ( Anas acuta ) from five important waterfowl wintering areas in California; (2) compare concentrations of organochlorines in selected species with emphasis on relationships to their diets; and (3) determine the relationship between concentrations of organochlorines in wings and carcasses of pintails. In the 1980-81 hunting season, we obtained wings of pintails, canvasbacks ( Aythya valisineria ), and lesser scaups ( A. affinis ) from the Pacific Flyway survey of waterfowl productivity, and we collected additional pintails and northern shovelers ( Anas clypeata ) in the Sacramento Valley. Concentrations of all compounds in pintail wings were below 1 ppm (wet weight), but residues were higher in wings from pintails shot late in the hunting season than early in the season, suggesting that accumulation of chemicals occurs while ducks are wintering in California. Highest concentrations were found in pintails from the southern regions and lowest in those from the northern regions of the state. DDE was significantly higher in males than in females. Wings of diving ducks were too few to enable statistical comparisons. Carcasses of shovelers contained residues of a wide array of organochlorines and significantly (P < 0.001) higher mean concentrations of DDE (0.68 ppm) than did pintails (0.12 ppm) collected at the same time and place. On a wet-weight basis, concentrations of DDE and DDT in the wings of pintails were about half those in the carcasses. Overall, concentrations of organochlorines were relatively low in all species and probably would have no effect on population survival or reproduction. However, some individuals contained elevated and possibly harmful levels of certain chemicals.

California↗
USGS1984

Responses of wintering bald eagles to boating activity

Wintering populations of bald eagles show a close association with open water (Spencer 1976, Steenhof 1978). With the dramatic increase in the use of waterways for recreational activity in recent decades (Brockman and Merriam 1973, Jensen 1973), concern has arisen regarding the effects of boating activity on wintering eagles (Stalmaster 1980). Boating activity can be detrimental because it disrupts feeding activity and affects large areas in short periods of time (Skagen 1980, Stalmaster 1980). Disturbance may result in increased energy expenditures due to avoidance flights and decreased energy intake due to interference with feeding activity (Stalmaster 1980). In this paper we examine flushing responses and flight distances of wintering bald eagles to a canoe of two adjacent rivers with widely disparate levels of boating activity. We examine individual and interactive effects of eagle age, behavior, and social grouping.

Journal of Wildlife Management↗
USGS1986

Survival estimates for North American Atlantic brant, 1956-75

The entire banding and recovery record for Atlantic brant (Branta bernicla hrota) was analyzed to determine recovery and survival rates for 1956-75. Composite survival rates for all adults (sex of banded birds was not recorded) during the 19-year period ranged from 0.984 to 0.591 (x = 0.785). Survival rates for Atlantic brant are relatively high among all geese but at the low end of the range for all brant. Detailed assessment of population structure and survival rates for each age and sex cohort are needed for this population.

Journal of Wildlife Management↗
USGS1986

Renesting Characteristics of Captive Mallards on Experimental Ponds

Renesting characteristics of captive wild-strain mallards (Anas platyrhynchos) were investigated on experimental ponds in southcentral North Dakota during the breeding seasons of 1976-81. Renesting efforts and egg production increased during the 1st 3 years. Post-yearling females that experienced clutch loss during early incubation produced 3 clutches of eggs during the breeding season. All of the birds produced 4 clutches and 50% produced 5 during the study. Birds provided with an unlimited food supply produced an average of 10.36 ± 1.03 (SD), 9.97 ± 1.09 (SD), 9.59 ± 0.91 (SD), 8.47 ± 0.94 (SD), and 8.50 ± 0.50 (SD) eggs during each successive nesting attempt. Clutch size differed (P < 0.01) among birds, ages, and nesting attempts. Renesting intervals for mallard females on unlimited food averaged 7.13 ± 1.24 (SD) days and ranged from 5 to 10 days. Intervals differed (P < 0.01) among birds and interval sequences. When food availability was reduced, renesting intervals increased and clutch size decreased.

North Dakota↗