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At least 973 records · Page 54Linked to original sources

An improved method of censusing deer in deciduous-coniferous forests

Aerial censusing has been used to determine densities of many large mammals, including deer ( Odocoileus virginianus ) in agricultural areas or deciduous forests (Saugstad 1942, Morse 1946, Petrides 1953, Sanderson 1953, Berner pers. comm.). However, observability of deer from the air remains a problem in northern coniferous forests. LeResche and Rausch (1974) determined that even with the much larger and more observable moose ( Alces alces ) during ideal snow conditions, experienced observers counted only 68% of a known number of animals; inexperienced observers counted 43%. Caughley (1974) and Caughley et al. (1976) suggested that the best solution to the problem of observability in aerial censuses is to measure the magnitude of the biases that exist, and correct estimates accordingly. This paper describes an attempt to measure observability bias in an aerial census of deer in deciduous coniferous habitat and to produce an accurate estimate of numbers.

Minnesota↗

Toxicity of experimental lead-iron shot versus commercial lead shot in mallards

The toxicity of an experimental lead-iron shot containing 38.1 percent lead was compared with commercial lead shot in mallard ducks (Anas platyrhynchos) fed corn for 14 weeks. Significantly higher mortality occurred in ducks dosed with commercial lead shot compared to ducks given lead-iron shot containing comparable amounts of lead. Loss of body weight was indicative of the difference in toxicity of the 2 types of shot. Mortality was dose related in ducks given commercial lead shot; one #8 shot (73 mg lead) caused 35 percent mortality with higher amounts of lead causing 80 to 100 percent mortality. Ingestion of up to 2 #4 lead-iron shot (111 mg lead) caused no significant weight loss and only 5 percent mortality. However, ducks dosed with 5 lead-iron shot suffered 45 percent mortality and those given 16 shot 50 percent mortality.

Journal of Wildlife Management↗

Habitat use by prairie raccoons during the waterfowl breeding season

Mobility and habitat use of raccoons ( Procyon lotor ) in an intensively farmed area of the prairie pothole region were studied during the waterfowl breeding seasons (April-July) of 1973-75. Over 5700 locations of 30 raccoons were analyzed. Movement patterns varied with sex, age, and reproductive status. Adult males moved regularly throughout slightly overlapping ranges that averaged 2560 ha. Yearling males dispersed during May-June but their movements before and after dispersal were similar. Parous or pregnant females (mostly adults) had ranges averaging 806 ha but their movements were confined to smaller areas near the litter site after parturition. Nulliparous yearling females did not disperse and their ranges averaged 656 ha. Building sites, wooded areas, and wetlands were the only habitats preferentially used both at night and during the day. Eighty-one percent of all nocturnal locations and 94 percent of all diurnal locations were in these 3 habitats which comprised only 10 percent of the study area. Use of building sites decreased concomitantly with increased use of wetlands. Upland habitats were seldom used.

Journal of Wildlife Management↗

Effects of radio packages on wild ducks

A total of 211 wild, free-flying mallards ( Anas platyrhynchos ) and wood ducks ( Aix sponsa ) were equipped with breast-mounted radio packages during the breeding seasons of 1968-72. Known predation loss was 7.6 and 12.0 percent for mallards and wood ducks respectively, 60 percent occurred within 3 weeks of instrumentation. The highest predation rate for mallards was 0.0048 kills per tracking day and 0.0136 for wood ducks. A higher direct recovery rate for instrumented birds (19.5 percent) than noninstrumented birds (8.1 percent) was probably due to the novelty of the transmitter to hunters. Departure patterns and locations of direct recoveries were similar between radio-equipped and normal-banded birds. Among female wood ducks with radios, recovery rates were lower than expected. Hunters indicated that 84 percent of the instrumented ducks recovered were in good or excellent condition. Recaptures of ducks as long as 1 year after being equipped with radio packages indicated that feather wear and skin abrasion were not serious. A high rate for feeding on land by instrumented mallards was probably due to our ability to more easily locate and observe these birds in cover. Preening rates were higher for instrumented ducks. As the birds became adjusted to the package, preening decreased and feeding on water increased. Social and breeding behavior of instrumented ducks did not appear to be adversely affected by the radio package.

Minnesota↗

Upland duck nesting related to land use and predator reduction

Duck nesting was studied during 1971 in north-central South Dakota under four conditions: in idle, five or six year old fields of domestic grass-legume mixtures in an area where predators including the red fox ( Vulpes fulva ), raccoon ( Procyon lotor ), striped skunk ( Mephitis mephitis ), and badger ( Taxidea taxus ) were (1) reduced and (2) not reduced. Nesting was also studied in tracts of active agricultural land (primarily croplands and pastures) where predators were (3) reduced, and (4) not reduced. Under condition (1), 260 nests were found on 0.87 km 2 (299 nests/km 2 ), eggs hatched in 92 percent of the nests and production was 22.0 ducklings/hectare. Under condition (2), 187 nests were found on 2.22 km 2 (84 nests/km 2 ), nest success was 68 percent and 4.7 ducklings/hectare were produced. On active agricultural land subject to predator reduction (condition 3), 64 nests were found on 5.14 km 2 (12 nests/km 2 ). Eggs in 85 percent of the nests hatched and production was 0.7 duckling/hectare. On active agricultural land not subject to predator reduction (condition 4), 58 nests were found on 4.01 km 2 (14 nests/km 2 ), nest success was 51 percent and 0.5 duckling/hectare was produced. Idle, 16 to 65-hectare (40 to 160-acre) stands of cool-season, introduced grasses in combination with legumes produced maximum numbers of upland nesting ducks.

South Dakota↗

Population dynamics of molting pintail drakes banded in south-central Saskatchewan

A total of 18,820 adult male pintails ( Anas acuta ) were trapped, banded, and released on Pel and Kutawagan marshes in south-central Saskatchewan in July 1955-58. Two hundred and fortyeight of these banded birds were recaptured on the same marshes during subsequent trapping operations, and 1,440 were recovered (shot or found dead) during legal hunting seasons, 1955-70. The size of the adult drake pintail population associated with Pel and Kutawagan marshes was estimated to have been approximately 313,600 in July 1956 and 232,800 in July 1957. Estimates of annual survival varied from approximately 60 percent to 85 percent with an average of 73 percent. Between July 1956 and July 1957, approximately 71,100 birds joined the population segment associated with Pel and Kutawagan marshes and 25,400 birds left the population segment for other areas. Indices to harvest pressure were low, varying from 2.26 in 1958 to 3.54 in 1956. Estimates of harvest rates varied from 5.6 percent to 8.8 percent, and kill rates varied from approximately 7.0 to 11.0 percent. The index to harvest pressure was highest in 1956, while survival during the 1956-57 period was the lowest, suggesting the possibility of an inverse relationship between harvest rate and total survival.

south-central Saskatchewan↗

Estimating survival rates from banding of adult and juvenile birds

The restrictive assumptions required by most available methods for estimating survival probabilities render them unsuitable for analyzing real banding data. A model is proposed which allows survival rates and recovery rates to vary with the calendar year, and also allows juveniles to have rates different from adults. In addition to survival rates and recovery rates, the differential vulnerability factors of juveniles relative to adults are estimated. Minimum values of the variances of the estimators are also given. The new procedure is applied to sets of duck and goose data in which reasonably large numbers of adult and juvenile birds were banded. The results are shown to be generally comparable to those procured by other methods, but, in addition, insight into the extent of annual variation is gained. Combining data from adults and juveniles also increases the effective sample size, since the juveniles are assumed to enter the adult age class after surviving their initial year.

Journal of Wildlife Management↗

Remote sensing for identification and classification of wetland vegetation

Multispectral photography and ground truth were obtained on an area 12 miles (19.3 km) east of Bemidji, Minnesota, to identify and map wetlands less than 2 acres (0.8 hectare) in size, to map emergent vegetation in lakes, and to explore the feasibility of classifying vegetation from aerial photographs. Wetlands less than 2 acres in size were identified on photography taken in May 1971, and emergent vegetation was recorded on purposely overexposed infrared black and white photography from a flight in September 1971. Several vegetation types and species groups were recognizable with the aid of color, color infrared, and black and white infrared photography. Proper timing of flights, use of multispectral photography, and knowledge of the ecology of the area are considered essential for wetland mapping by remote sensing.

Minnesota↗

Supplemental feeding program for California condors

A 2-year supplemental feeding program for the endangered California condor ( Gymnogyps californianus ) was of insufficient length to definitely show that a dependable food supply will stimulate additional breeding; however, production did increase during the study, and food supply appears a likely cause. Because no undesirable effects of feeding were noted, and because condor production is now critically low, an expanded supplemental feeding program is recommended.

California↗

Metabolic indicators of habitat differences in four Minnesota deer populations

Blood samples were collected from 40 white-tailed deer ( Odocoileus virginianus ) from 4 winter yards in northeastern Minnesota from 17 March 1974 through 23 April 1975. The results of 26 blood assays were examined for the effects of age, sex, capture date, capture method, disease and location. Age-related effects were found for serum chloride, calcium, gamma globulin, creatine phosphokinase (CPK), lactic dehydrogenase (LDH), and alkaline phosphatase. The only sex difference was lower CPK in males. Date of collection effects were found for erythrocyte count, mean corpuscular volume (MCV), serum glucose, and nonesterified fatty acids (NEF A). Capture method affected serum glucose, acid base balance, and serum enzymes. Effects related primarily to capture location or habitat differences were found for erythrocyte count, MCV, mean corpuscular hemoglobin concentration (MCHC), serum urea, cholesterol, LDH, thyroxine, and NEF A. Animals whose assays indicated the poorest nutritional status inhabited wintering areas with the oldest vegetation. Habitat differences can be detected by measuring the physiological status of the local animal populations.

Minnesota↗

Reappraising factors affecting mourning dove perch coos

Results confirmed pairing as the primary factor influencing perch-cooing rates of wild mourning doves ( Zenaida macroura ). Marked unmated males cooed at substantially higher rates (6.2x) than mated males, had greater probability of cooing (2.3x) during 3-minute periods, and continued cooing longer each morning than mated males. Population density was not a major factor affecting cooing. Unmated males cooed more frequently in the presence of other cooing doves (P < 0.05) than when alone, but the number of additional doves above 1 was unimportant. Cooing rates of both mated and unmated males on areas with dissimilar dove densities were not significantly different. Within limits of standard call-count procedure, weather exerted no detectable influence on cooing.

South Carolina↗

Interpreting the results of nesting studies

Nesting studies are used to assess the production of birds and to evaluate nesting habitats. Most such studies involve finding nests in a given area and subsequently determining the proportion that hatched. Unfortunately, the results are often biased by unrecognized differences in the probabilities of finding successful and unsuccessful nests. The observed hatch rates of 1,900 nests of blue-winged teal ( Anas discors ) are presented to illustrate the relationship of hatch rates to time remaining until the nests should hatch. The Mayfield method of correcting for these biases is illustrated. Other examples demonstrate the possible effects of sampling procedures on observed hatch rates and nest density.

Journal of Wildlife Management↗

Red fox prey demands and implications to prairie duck production

Experiments were conducted during spring and summer with 33 red foxes ( Vulpes vulpes ) to determine prey demands, feeding characteristics, and growth rates using natural foods. Pups began eating prey the 4th week after birth. Then, prey consumption averaged 1.38 and 1.90 kg/pup/week for weeks 5-8 and 9-12 of the denning season respectively, and 2.54 kg/pup/week for the postdenning period. Feeding by adults averaged 2.25 kg/adult/week. Free water was not needed by either pups or adults. About 90 percent of the prey offered to pups on simulated natural diets was consumed, remains varied with prey availability and prey type. Prey biomass required by a typical fox family was estimated at 18.5 kg/km2 for the 12-week denning season and 2.4 kg/km2/week for the postdenning period. Because of the large prey demands, ducks could represent a small part of the foxes' diet and yet be of consequence to the productivity of particular species. An example is provided for the mallard ( Anas platyrhynchos ).

Journal of Wildlife Management↗

Relating wolf scat content to prey consumed

In 9 trials, captive wolves ( Canis lupus ) were fed prey varying in size from snowshoe hares ( Lepus americanus ) to adult deer ( Odocoileus virginianus ), and the resulting scats were counted. Field-collectible scats were distinguished from liquid, non-collectible stools. I n collectible scats, the remains of small prey occurred in greater proportion relative to the prey's weight, and in lesser proportion relative to the prey's numbers, than did the remains of larger prey. A regression equation with an excellent, fit to the data (r2 = 0.97) was derived to estimate the weight of prey eaten per collectible scat for any prey. With this information and average prey weights, the relative numbers of different prey eaten also can be calculated.

Journal of Wildlife Management↗

Age and sex determination of juvenile band-tailed pigeons

Captive band-tailed pigeons ( Columba fasciata ) were studied to document progression of molts and plumages from juvenal to adult age. Immature pigeons began the post-juvenal molt at 35 days which continued up to 340 days. The only 3 plumage characters useful for identification and estimation of age were presence of juvenal lesser, middle, and greater secondary coverts, juvenal secondaries, and juvenal primaries. While juvenal primaries were still present, hatching dates could be estimated up to 252 days (N = 84). Secondary feather presence and molt stage could be used to identify juvenile pigeons for more than 340 days (N = 24). Using coloration of the crown and breast feathers, 96 percent of the immature pigeons examined (106 of 110) at 80 days of age were classified accurately as to sex.

Journal of Wildlife Management↗

Erythrocyte δ-Aminolevulinic Acid Dehydratase Activity in Mallard Ducks: Duration of Inhibition after Lead Shot Dosage

Inhibition of a lead-specific blood enzyme, 8-aminolevulinic acid dehydratase (ALAD), has been utilized to indicate the incidence and degree of lead contamination in canvasback ducks ( Aythya valisineria ) (Dieter et al. 1976). This variable was found to be more sensitive to lead than previous tests that have been employed with waterfowl (Locke et al. 1966, 1967), and has proved to be completely reliable (Finley et al. 1976a,b). However, it is not yet known how long ALAD enzyme inhibition persists after a source of high head contamination is removed. The duration of inhibition is critical because too brief a response would result in underestimating the extent of lead contamination in a given year's survey. Moreover, the ALAD enzyme bioassay can be used to identify ducks that have ingested lead shot, as well as those that have ingested low levels of lead in their forage, and this information used to help remove the source of the environmental contamination.

Maryland↗