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At least 1,063 records · Page 59Linked to original sources
USGS1986

Physiological condition of autumn-banded mallards and its relationship to hunting vulnerability

An important topic of waterfowl ecology concerns the relationship between the physiological condition of ducks during the nonbreeding season and fitness, i.e., survival and future reproductive success. We investigated this subject using direct band recovery records of mallards ( Anas platyrhynchos ) banded in autumn (1 Oct-15 Dec) 1981-83 in the Mississippi Alluvial Valley (MAV) [USA]. A condition index, weight (g)/wing length (mm), was calculated for each duck, and we tested whether condition of mallards at time of banding was related to their probability of recovery during the hunting season. In 3 years, 5,610 mallards were banded and there were 234 direct recoveries. Three binary regression model was used to test the relationship between recovery probability and condition. Likelihood-ratio tests were conducted to determine the most suitable model. For mallards banded in autumn there was a negative relationship between physical condition and the probability of recovery. Mallards in poor condition at the time of banding had a greater probability of being recovered during the hunting season. In general, this was true for all ages and sex classes; however, the strongest relationship occurred for adult males.

Arkansas, Illinois, Kentucky, Louisiana, Mississip↗
USGS1986

Northern pintail body condition during wet and dry winters in the Sacramento Valley, California

Body weights and carcass composition of male and female adult northern pintails ( Anas acuta ) were investigated in the Sacramento Valley, California, from August to March 1979-82. Pintails were lightweight, lean, and had reduced breast, leg, and heart muscles during August-September. Ducks steadily gained weight after arrival; and body, carcass (body wt minus feathers and gastrointestinal content), fat protein, and muscle weights peaked in October-November. Fat-free dry weight remained high but variable the rest of the winter, whereas body and carcass weight and fat content declined to lows in December or January, then increased again in February or March. Gizzard weights declined from early fall to March. Males were always heavier than females, but females were fatter (percentage) than males during mid-winter. Mid-winter body weight, carcass fat, and protein content were significantly (P < 0.01) lower in the dry winter of 1980-81 than in 2 wet winters (1979-80 and 1981-82). Changes in pintail body weight and composition during winter are probably adaptations to mild climate, predictable food supplies, and requirements for pair formation and molt.

California↗
USGS1995

Geographic variation in band reporting rates for mallards based on reward banding

We conducted a reward band study on mallards ( Anas platyrhynchos ) to estimate and test hypotheses about sources of variation in band reporting rate. We banded 25,398 mallards with standard and 100 reward bands (3 mallards banded with standard bands for every reward-banded mallard) during preseason (Jul-Sep), 1988. We used a series of multinomial models to model the resulting 2,776 band recoveries from 1988 to 1991. Estimates of reporting rate for males shot in 10 harvest areas ranged from 0.29 to 0.46 and averaged 0.38 (SE = 0.020). We found evidence ( P < 0.01) of geographic variation in reporting rates, but not of smooth latitudinal or longitudinal gradients. There was evidence ( P = 0.07) of lower reporting rates for females than males, especially in prairie Canada and the Central Flyway. Except for young males in the northern Atlantic Flyway, estimated harvest rates were lower than historical estimates, as expected from recent restrictive hunting regulations. Patterns of geographic and agesex variation in harvest rates were similar to those obtained using historical band-recovery data.

Journal of Wildlife Management↗
USGS1995

Robustness of survival estimates from radio-telemetry studies with uncertain relocation of individuals

Traditional methods of estimating survival from radio-telemetry studies use either the Trent-Rongstad approach (Trent and Rongstad 1974, Heisey and Fuller 1985) or the Kaplan-Meier approach (Kaplan and Meier 1958; Pollock et al. 1989 a , b ). Both methods appear to require the assumption that relocation probability for animals with a functioning radio is 1. In practice this may not always be reasonable and, in fact, is unnecessary. The number of animals at risk (i.e., risk set) can be modified to account for uncertain relocation of individuals. This involves including only relocated animals in the risk set instead of also including animals not relocated but that were seen later. Simulation results show that estimators and tests for comparing survival curves should be based on this modification.

Journal of Wildlife Management↗
USGS1998

Reproductive performance of female Alaskan caribou

We examined the reproductive performance of female caribou ( Rangifer tarandus granti ) in relation to age, physical condition, and reproductive experience for 9 consecutive years (1987-95) at Denali National Park, Alaska, during a period of wide variation in winter snowfall. Caribou in Denali differed from other cervid populations where reproductive performance has been investigated, because they occur at low densities (≥0.3/km 2 ) and experience high losses of young to predation. Females first gave birth at 2-6 years old; 56% of these females were 3 years old. Average annual natality rates increased from 27% for 2-year-olds to 100% for 7-year-olds, remained high for 7-13-year-olds (98%), and then declined for females ≥14 years old. Females ≥2 years old that failed to reproduce were primarily sexually immature (76%). Reproductive pauses of sexually mature females occurred predominantly in young (3-6 yr old) and old (≥14 yr old) females. Natality increased with body mass for 10-month-old females weighed 6 months prior to the autumn breeding season (P = 0.007), and for females >1 year old and weighed during autumn (late Sep-early Nov; P = 0.003). Natality for 2-, 3-, 4-, and 6-year-olds declined with increasing late-winter snowfall (Feb-May; P ≤ 0.039) during the winter prior to breeding. In most years, a high percentage of sexually mature females reproduced, and lactation status at the time of breeding did not influence productivity the following year. However, following particularly high snowfall during February-September 1992, productivity was reduced in 1993 for cows successfully rearing calves to autumn the previous year. High losses of calves to predators in 1992 may have increased productivity in 1993. Losses of young-of-the-year to predation prior to the annual breeding season can be an important influence on subsequent productivity for ungulate populations where productivity varies with lactation status of females at the time of breeding.

Journal of Wildlife Management↗
USGS1998

Interpreting carnivore scent-station surveys

The scent-station survey method has been widely used to estimate trends in carnivore abundance. However, statistical properties of scent-station data are poorly understood, and the relation between scent-station indices and carnivore abundance has not been adequately evaluated. We assessed properties of scent-station indices by analyzing data collected in Minnesota during 1986-03. Visits to stations separated by <2 km were correlated for all species because individual carnivores sometimes visited several stations in succession. Thus, visits to stations had an intractable statistical distribution. Dichotomizing results for lines of 10 stations (0 or ≥ 1 visits) produced binomially distributed data that were robust to multiple visits by individuals. We abandoned 2-way comparisons among years in favor of tests for population trend, which are less susceptible to bias, and analyzed results separately for biogeographic sections of Minnesota because trends differed among sections. Before drawing inferences about carnivore population trends, we reevaluated published validation experiments. Results implicated low statistical power and confounding as possible explanations for equivocal or conflicting results of validation efforts. Long-term trends in visitation rates probably reflect real changes in populations, but poor spatial and temporal resolution, susceptibility to confounding, and low statistical power limit the usefulness of this survey method.

Minnesota↗
USGS1998

Causes and rates of mortality of swift foxes in western Kansas

Knowledge of mortality factors is important for developing strategies to conserve the swift fox (Vulpes velox), a species being considered for listing under the Endangered Species Act, but available information about swift fox mortality is inadequate. We used radiotelemetry techniques to examine the magnitude and causes of mortality of swift fox populations in 2 study areas in western Kansas. One study area was predominantly cropland, the other rangeland. Mortality rates, calculated using Kaplan-Meier estimation techniques in a staggered entry design, were 0.55 ?? 0.08 (5 ?? SE) for adult and 0.67 ?? 0.08 for juvenile swift foxes. We did not detect differences between study areas in mortality rates for adults or juveniles. Predation by coyotes (Canis latrans) was the major cause of mortality for adult and juvenile swift foxes in both study areas, and vehicle collision was an important mortality factor for juveniles in the cropland study area. No mortality was attributed to starvation or disease.

Journal of Wildlife Management↗
USGS1998

Red-shouldered hawk broadcast surveys: Factors affecting detection of responses and population trends

Forest-nesting raptors are often difficult to detect and monitor because they can be secretive, and their nests can be difficult to locate. Some species, however, respond to broadcasts of taped calls, and these responses may be useful both in monitoring population trends and in locating nests. We conducted broadcast surveys on roads and at active red-shouldered hawk ( Buteo lineatus ) nests in northcentral Minnesota to determine effects of type of call (conspecific or great horned owl [ Bubo virginianus ]), time of day, and phase of the breeding cycle on red-shouldered hawk response behavior and to evaluate usefulness of broadcasts as a population monitoring tool using area occupied-probability-of-detection techniques. During the breeding seasons of 1994 and 1995, we surveyed 4 10-station road transects 59 times and conducted 76 surveys at 24 active nests. Results of these surveys indicated conspecific calls broadcast prior to hatch and early in the day were the most effective method of detecting red-shouldered hawks. Probability of detection via conspecific calls averaged 0.25, and area occupied was 100%. Computer simulations using these field data indicated broadcast surveys have the potential to be used as a population monitoring tool.

Minnesota↗
USGS1998

Evaluation of transmitter attachment techniques on growth of wild turkey poults

We compared the effects on growth of backpack-mounted and surgically implanted radiotransmitters used as marking techniques in studies of wild turkey ( Meleagris gallopavo ) poult survival. We applied repeated-measures analysis of variance (ANOVA) and Bayesian analysis to evaluate the null hypothesis that marking technique did not affect growth. Growth in body mass was similar among treatment groups. We did, however, find differences in wing-growth rates among treatment groups. The control group had the highest wing-growth rate, the backpack group had the lowest growth rate, and the surgical implant group was intermediate. Latex backpack harnesses also caused physical developmental problems that would have negatively biased wild poult survival estimates in the field. Surgically implanted transmitters affected wing growth less than the backpack harnesses and are therefore recommended for attaching transmitters to wild turkey poults.

Journal of Wildlife Management↗
USGS1996

Implanting intra-abdominal radiotransmitters with external whip antennas in ducks

We developed and evaluated a surgical procedure for implanting intra-abdominal radiotransmitters with external whip antennas in captive mallards ( Anas platyrhynchos ). Transmitters were implanted in the abdominal cavity and the antennas exited through the caudal abdominal wall and skin. Birds with implanted transmitters developed mild to moderate localized air sac reactions. These reactions involved adhesions of the right anterior abdominal air sac to the liver with contractions around the transmitters and antenna catheters. The adhesions were reinforced by a proliferation of connective tissue and lined by multinucleated giant cells (foreign body reaction). Casual observation indicated that neither behavior nor activity of the birds was altered by the histological reaction to the transmitter implant. No increase in systemic lesions (particularly liver or kidney) could be correlated with the histological reactions. Our evaluations indicate that the procedure is a reliable method for radiomarking ducks and the technique has been successfully used in 2 field studies.

Journal of Wildlife Management↗
USGS1996

Thermoregulatory effects of radiotelemetry transmitters on mallard ducklings

Many telemetry transmitter attachments disrupt downy insulation, and may bias survival studies during cold weather by making ducklings more susceptible to chilling. We compared thermal responses of untreated 1-day-old mallards ( Anas platyrhynchos ) to ducklings carrying external sutured backpack or subcutaneously implanted transmitters. Ducklings carrying external transmitters showed areas of increased surface temperature in thermographic images. However, open-circuit respirometry studies at 5, 10, 15, 20, and 25 C and wind speeds of 0.1, 0.2, 0.5, and 1 m/s indicated no biologically significant differences in total heat production, net heat production, or short-term body mass loss. These results do not exclude the possibility of other negative effects of transmitters on duckling behavior and survival.

Journal of Wildlife Management↗
USGS1997

Analysis of habitat selection studies with multiple patches within cover types

Current statistical methods are inadequate for evaluation of the relation between spatial pattern of the landscape and observed patterns of habitat use by individuals or populations. For example, traditional habitat selection analysis methods do not use information about the size and distribution of the several patches of each cover type that may exist within the study area. Statistical tests are presented for hypotheses about disproportional use of cover types and patches within cover types. These tests require that use of individual patches is recorded, as well as the size of individual patches. Different designs are considered in which there are (1) single or multiple samples of use, and (2) equal or unequal habitat availability. Formulas for calculating Type II statistical errors of the tests are presented and Monte Carlo simulation is used to assess the accuracy of the formulas and to check the Type I error rates of the proposed test statistics. With adequate sample sizes, Type II error formulas can be a useful tool for planning of habitat selection studies. An example analysis is presented of a hypothetical study of habitat selection by ring-necked pheasants ( Phasianus colchicus ) in a Midwestern landscape. The proposed tests also represent a contribution toward bringing together concepts of landscape ecology and wildlife habitat selection.

Journal of Wildlife Management↗
USGS1997

Spring feeding on ungulate carcasses by grizzly bears in Yellowstone National Park

We studied the spring use of ungulate carcasses by grizzly bears ( Ursus arctos horribilis ) on ungulate winter ranges in Yellowstone National Park. We observed carcasses and bear tracks on survey routes that were travelled biweekly during spring of 1985-90 in the Firehole-Gibbon winter range and spring of 1987-90 in the Northern winter range. The probability that grizzly bears used a carcass was positively related to elevation and was lower within 400 m of a road, or within 5 km of a major recreational development compared to elsewhere. Carcass use peaked in April, coincident with peak ungulate deaths. Grizzly bears also were more likely to use carcasses in the Firehole-Gibbon compared to Northern Range study area. We attributed the effects of study area and elevation to the fact that grizzly bears den and are first active in the spring at high elevations and to differences in densities of competing scavengers. Probability of grizzly bear use was strongly related to body mass of carcasses on the Northern Range where densities of coyotes ( Canis latrans ) and black bears ( U. americanus ) appeared to be much higher than in the Firehole-Gibbon study area. We suggest that additional restrictions on human activity in ungulate winter ranges or movement of carcasses to remote areas could increase grizzly bear use of carrion. Fewer competing scavengers and greater numbers of adult ungulates vulnerable to winter mortality could have the same effect.

Wyoming↗
USGS1997

A survey for mallard pairs in the Atlantic flyway

During 1989-1992, spring surveys of randomly selected, 1-km 2 plots, stratified by physiographic strata, were conducted in the Atlantic flyway from New Hampshire to Virginia, to estimate mallard ( Anas platyrhynchos ) pairs. All potential waterfowl habitat in each plot was checked by ground crews. The adjusted mean mallard pair estimate over the 4-year period was 300,849 (range 271,193-320,642, mean SE 22,455) for the region surveyed. Ground plot checks are a practical way to survey mallard pairs in the upper Atlantic flyway.

Connecticut, Delaware, Maryland, Massachusetts, Ne↗
USGS1997

Survival rates of American woodcock wintering in the Georgia Piedmont

We estimated survival rates of wintering American woodcock ( Scolopax minor ). We found no age- or sex-specific differences in period survival rates. The survival rate for the period 25 December 1994-7 February 1995 for all age and sex classes combined (0.72) was not different from a similarly derived estimate for woodcock wintering along the Atlantic Coast. Survival rates of wintering woodcock are relatively low compared to other seasons.

Georgia↗
USGS1997

Seasonal and annual survival of adult Pacific brant

Declining mid-winter counts of Pacific brant ( Branta bernicla nigricans ) and reduced numbers of nesting birds on their main breeding grounds prompted us to assess factors that may be limiting recovery of this population. We estimated seasonal and annual survival rates of adult brant in 1986-93 from resightings of leg-banded birds. Brant were banded at a major colony on the Yukon-Kuskokwim Delta, Alaska (Y-K Delta) in 1986-92, and resighted there in 1987-93 as well as at major fall and spring migration and wintering areas in 1990-93. Seasonal survival was the same for males and females. Mean monthly survival rate was lowest (P ≤ 0.05) in late spring migration (15 Apr-1 Jun), the period of greatest subsistence harvest on the breeding grounds, and highest in winter (1 Jan-1 Mar), the period of greatest sport harvest. Annual survival rate did not vary among years (F = 0.51; 5, 718 df; P = 0.91) and averaged 0.840 (SE = 0.031) from 1986 to 1993. Subsistence harvest has contributed to low population levels of Pacific brant.

Alaska↗