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At least 1,063 records · Page 59Linked to original sources
USGS1988

A double survey estimate for sighting probability of sea otters in California

We developed an estimator for the probability of sighting sea otters ( Enhydra lutris ) by shore- based counters, based on simultaneous double-surveys. We then estimated probability of sighting sea otters in California and evaluated the estimator's principal assumptions. The overall probability of sighting sea otters on 5 replicated double-surveys at each of 6 study areas was 0.945. Estimated probability of sighting did not vary (P > 0.05) among study areas or over time and was not correlated (P > 0.05) with distance of otters from observers. Probability of sighting was affected (P < 0.05) by sea otter activity and group size. Activity-specific probabilities of sighting were: resting = 0.990, foraging = 0.769, and other = 0.885. All animals missed by 1 observer team were in groups of ≤ 2 otters, whereas 52% of the animals sighted during the study were in groups ≥ 3. Observer teams may have varied slightly in sighting ability, but this variation did not substantially affect population estimates.

California↗
USGS1986

Influence of nutrients on feed intake and condition of captive canvasbacks in winter

Dramatic changes in the food habits and distribution of canvasbacks ( Aythya valisineria ) in Chesapeake Bay during the 1970's generated a need to evaluate the nutritional value of food items and the requirements of this species on its wintering grounds. Groups of captive canvasbacks were maintained ad libitum on 5 diets during the winters of 1978-79 and 1979-80 to evaluate the effects of varying protein and energy levels on feed intake and condition. Feed intake during the 1979-80 winter was 42% greater for those ducks fed the low energy (1,543 kcal/kg) diet than for those fed the high energy (3,638 kcal/kg) diet. Canvasbacks fed the high energy diet, however, consumed 317 kcal/bird day, whereas those fed the low energy diet consumed only 191 kcal/bird day. Body weight of males and females did not differ among groups fed different diets, but there were seasonal differences (P < 0.05) for both sexes aggregated across diets. Data from this study indicate that canvasbacks may be unable to adjust intake rates to compensate for low energy foods and subsequently may store less fat or modify behavior. However, decreased weight, feed intake, and activity of ducks fed ad libitum rations occurred in mid-winter irrespective of diet quality and appeared to be an endogenous component of their annual cycle that persists in captivity. These changes apparently have a selective advantage of increasing the probability of survival in ducks by decreasing energy expenditure during periods of winter stress.

Maryland, Virginia↗
USGS1986

Blood chemistry and hematocrit of captive and wild canvasbacks

Blood chemistry and packed cell volume (PCV) did not vary among groups of captive canvasbacks ( Aythya valisineria ) maintained ad libitum on 5 diets varying in metabolizable energy (ME) and protein. Ducks fed low quality diets increased their consumption so that all ducks were obtaining similar amounts of energy and protein. Some variables, including cholesterol, were found to differ between the sexes and ages of captive ducks. Seasonal differences were detected in the blood chemistry of captive canvasbacks. Four of the 5 enzyme values increased from October to January and then declined to April. PCV increased from 45 in October to 51 in April. Overall, blood chemistry values and PCV's were highly variable and did not appear to be good discriminators for age, sex, and diet of captive canvasbacks. Differences detected between captive and wild canvasbacks were attributed to increased stress of wild ducks during handling.

Journal of Wildlife Management↗
USGS1986

Relationship between snow depth and gray wolf predation on white-tailed deer

Survival of 203 yearling and adult white-tailed deer ( Odocoileus virginianus ) was monitored for 23,441 deer days from January through April 1975-85 in northeastern Minnesota. Gray wolf ( Canis lupus ) predation was the primary mortality cause, and from year to year during this period, the mean predation rate ranged from 0.00 to 0.29. The sum of weekly snow depths/month explained 51% of the variation in annual wolf predation rate, with the highest predation during the deepest snow.

Minnesota↗
USGS1986

Shrinkage and growth compensation in common sunflowers: refining estimates of damage

Shrinkage and growth compensation of artificially damaged common sunflowers ( Helianthus annuus ) were studied in central North Dakota during 1981-1982 in an effort to increase accuracy of estimates of blackbird damage to sunflowers. In both years, as plants matured damaged areas on seedheads shrank at a greater rate than the sunflower heads themselves. This differential shrinkage resulted in an underestimation of the area damaged. Sunflower head and damaged-area shrinkage varied widely by time and degree of damage and by size of the seedhead damaged. Because variation in shrinkage by time of damage was so large, predicting when blackbird damage occurs may be the most important factor in estimating seed loss. Yield'occupied seed area was greater ( P < 0.05) for damaged than undamaged heads and tended to increase as degree of damage inflicted increased, indicating growth compensation was occurring in response to lost seeds. Yields of undamaged seeds in seedheads damaged during early seed development were higher than those of heads damaged later. This suggested that there was a period of maximal response to damage when plants were best able to redirect growth to seeds remaining in the head. Sunflowers appear to be able to compensate for damage of ≤ 15% of the total hear area. Estimates of damage can be improved by applying empirical results of differential shrinkage and growth compensations.

Journal of Wildlife Management↗
USGS1989

Physiological assessment of deer populations by analysis of urine in snow

We compared the nutritional status of free-ranging white-tailed deer ( Odocoileus virginianus ) in 3 natural yards and 1 yard where deer were supplementally fed from 1 January to 31 March 1985 in northeastern Minnesota. We monitored deer nutritonal status by sequential collection and chemical analysis of urine in snow (snow-urine) for urea nitrogen (U), sodium (Na), potassium (K), calcium (Ca), and phosphorus (P). Dilution of urine by snow was corrected by comparing these data as ratios to creatinine (C). All deer remained in an early phase of undernutrition; however, declining trends of U:C, Na:C, and K:C in 2 natural yards indicated increasingly inadequate nutrition as winter progressed. Unaltered values of these ratios and P.C in snow-urine collected from the third natural yard reflected stable levels of nutrient availability. Significant (P < 0.05) elevations of Na:C, K:C, and P:C in 2 natural yards with similar snow regimes suggested initiation of nutritional recovery in deer during late March. In contrast, deep snow in the third natural yard restricted feeding activity and was associated with ratios that remained diminished. Elevated U:C, Na:C, and K:C provided physiological evidence of the higher nutritional status of supplementally fed deer throughout winter and their ability to increase nutrient intake during late March despite prolonged deep snow cover. Frequent and quantitative assessments of the physiological status of deer by snow-urine analysis provided an improved understanding of the relationship between snow cover and the nutritional well-being of these deer.

Minnesota↗
USGS1989

Impaired reproduction of mallards fed an organic form of selenium

We fed mallards ( Anas platyrhynchos ) diets supplemented with 0-, 1-, 2-, 4-, 8-, or 16-ppm selenium in the form of selenomethionine. We fed another group of mallards a diet containing 16-ppm selenium as selenocystine. Females fed the control diet produced a mean of 8.1 ducklings that survived to 6 days of age, which was significantly greater than the 4.6 young produced by females fed 8-ppm selenium as selenomethionine and the zero surviving young of females fed 16-ppm selenium as selenomethionine. Selenocystine did not impair reproduction. Diets containing 8- and 16-ppm selenium as selenomethionine caused malformations in 6.8 and 67.9%, respectively, of unhatched eggs compared with 0.6% for controls. The most common malformations were of eyes, bill, legs, and feet. Selenium did not affect the onset or frequency of egg laying, egg size, shell thickness, fertility of eggs, or sex ratio of ducklings. Reduced survival and growth occurred in ducklings hatched from groups whose parents had received 8- or 16-ppm selenium as selenomethionine, even though all ducklings were fed a control diet. Concentrations of selenium in eggs and liver of adults could be predicted from dietary concentrations. We conclude that the dietary threshold of selenium as selenomethionine necessary to impair reproduction is between 4 and 8 ppm. It is difficult to identify 1 level of selenium in eggs that will be diagnostic of reproductive impairment in the field because different chemical forms of selenium appear to have different toxicities in eggs. However, when eggs from a wild population contain .gtoreq. 1-ppm selenium on a wet-weight basis, reproductive impairment may be possible and should be evaluated in that population. At 5-ppm selenium in eggs, reproductive impairment is much more likely to occur.

Journal of Wildlife Management↗
USGS1989

Mallard survival from local to immature stage in southwestern Saskatchewan

We used 3,670 recoveries from 32,647 bandings of mallards ( Anas platyrhynchos ) in southwestern Saskatchewan during 1956-59 to estimate the probability of surviving from the local, flightless (classes II and III) stage to the flighted, immature stage. The probability of surviving from the local to the immature stage was 0.84 ± 0.05 (SE) for males and females. The geographic distribution of direct recoveries was similar for the birds banded as local and immature. Probabilities of survival for banded mallards can only be estimated from late summer to late summer. The estimate of survival from local to immature stage fills a gap in our knowledge of mallard mortality from female-brood breakup to the time of banding in late summer.

southwestern Saskatchewan↗
USGS1989

Attendance patterns of murres at breeding sites: Implications for monitoring

We studied attendance patterns (presence and absence at breeding sites) of common murres ( Uria aalge ) and thick-billed murres ( U. lomvia ) at a colony in the Semidi Islands, western Gulf of Alaska. The period from mid-laying through hatching was appropriate for censusing because counts were subject to the least amount of daily variation. Time of day and weather did not have large effects on the counts and serial dependence was weak or absent. A trend in murre numbers during the census period occurred in 2 of 4 years but the direction of change was inconsistent. Counts made on 40 consecutive days were needed to detect a 6-8% change in numbers between years, whereas 5 counts were adequate to detect a 20-26% change in numbers. Annual changes in murre numbers varied among study plots but mean combined counts differed by 6-16% between years. Behavioral differences alone were inadequate to explain the annual variation in plot counts because site occupancy rates of individual murres were relatively constant.

Alaska↗
USGS1984

Nest spacing, habitat selection, and behavior of waterfowl on Miller Lake Island, North Dakota

The nesting behavior of a concentration of nesting mallards ( Anas platyrhynchos ) and gadwalls ( A. strepera ) was studied on a 4.5-ha island in Miller Lake, North Dakota, in 1977. A single 0.59-ha clump of thick shrub contained 225 simultaneously active mallard nests on 10 May. During the peak nesting period, mallard nests were spaced an average of 2.7 m from conspecifics. Active nests of all species peaked at 327, spaced an average of 2.1 m apart. Nests were clustered in thick shrub with moderate numbers in open shrub and few in grassland. Nest placement was significantly related to the amount of vegetative screening although mammalian predators were absent on the island. Cover density appeared to be important to the nesting hens as vegetation screened nests from potential avian predators and from harassment by other conspecific nesting hens and drakes. Mallards and gadwalls nesting on this island used wetlands in >100 km2 around Miller Lake. During daylight hours in late April 1978, an average of 4.9 mallards/minute arrived at the island; a peak of 17.2 mallards/minute arrived at 0800. In late April 1978, as many as 26 mallard pairs/ha occurred on favored wetlands and behavioral aggression was intense. Yet, most mallard hens maintained adequate space to acquire food and other requisites. Mallards and gadwalls were sufficiently adaptable to successfully exploit the Miller Lake island and environments that resulted in high reproductive success. Other local breeding Anatidae because of behavioral constraints were unable to exploit the same situation.

North Dakota↗
USGS1984

Comparative ability of northern pintails, gadwalls, and northern shovelers to metabolize foods

Feeding trials were used to compare the ability of northern pintails ( Anas acuta ), gadwalls ( A. strepera ), and northern shovelers ( A. clypeata ) to metabolize energy from a turkey starter ration, alfalfa pellets, and common barnyardgrass ( Echinochloa crusgalli ) seeds. No differences (P > 0.05) were detected among the three species for any of the three foods (kg body weight/day basis), for dry matter intake (DMI), body weight gain (BWG), apparent metabolizable energy (AME), or metabolized energy (MEE) on any given diet consumed in quantities large enough to promote body weight gain. The AME content of alfalfa was 57% less than the value for turkey starter and 50% less than for barnyardgrass seeds. All three species metabolized more energy and gained weight faster when fed turkey starter. Energy modeling may be facilitated if additional research verifies that all species of dabbling ducks have equal ability to obtain energy from foods available to them in the wild. Behavioral and morphological factors may be more important in defining feeding niches than digestive physiology, at least for the three duck species tested, at the time of year of the experiments, and within the limits of the quality of foods used.

Journal of Wildlife Management↗
USGS1984

Ecological distribution and crude density of breeding birds on prairie wetlands

Breeding populations of 28 species of wetland-dwelling birds other than waterfowl (Anatidae) were censused on 1,321 wetlands lying within the prairie pothole region of North Dakota. Ecological distribution and two crude measures of relative density were calculated for the 22 commonest species using eight wetland classes. Semipermanent wetlands supported nearly two-thirds of the population and were used by all 22 species, whereas seasonal wetlands contained about one-third of the population and were used by 20 species Semipermanent, fen, and temporary wetlands contained highest bird densities on the basis of wetland area; on the basis of wetland unit, densities were highest on semipermanent, permanent, alkali, and fen wetlands. The highest ranking of semipermanent wetlands by all three measures of use was probably because these wetlands, as well as being relatively numerous and large, were vegetatively diverse. The fairly large proportion of the bird population supported by seasonal wetlands was a result of wetland abundance and moderate vegetative diversity. Increased vegetative diversity results from the development of characteristic zones of hydrophytes at sites where water persists longer during the growing season. Frequent cultivation of prairie wetlands results in the replacement of tall, robust perennials by bare soil or stands of short, weak-stemmed annuals that likely are unattractive to nesting birds.

North Dakota↗
USGS1988

Survival of juvenile ring-necked ducks on wetlands of different pH

Brood and duckling survival of ring-necked ducks ( Aythya collaris ) was examined in relation to wetland water chemistry in eastcentral Maine during 1983-85. Daily survival rates (DSR) of broods and ducklings were determined for 381 ducklings from 64 broods by counts of each brood at 6-10-day intervals during broodrearing. Twelve of 64 females lost entire broods. Only 176 of 381 (46%) ducklings survived to fledge. Brood survival for the 45-day rearing period was 0.7731; duckling survival was 0.3707. Young ducklings ( ≤ 24 days) survived at a lower rate (0.9750/day) than older ( ≥ 25 days) ducklings (0.9818/day) ( P = 0.002). Survival rates of broods and ducklings did not differ among wetlands of high and low alkalinities. Brood survival did not differ among wetlands of different pH, but DSR of ducklings was lower (0.9763/day) on low-pH (<6.0) wetlands than on high-pH ( ≥ 6.1) wetlands (0.9816/day) ( P = 0.049). Class IIb-III (25-45 days old) ducklings from the lowest-pH wetlands(<5.5) had the lowest DSR (0.9752) while Class IIb-III ducklings from the highest-pH wetlands (>6.5) had the highest DSR (0.9856) ( P = 0.009).

Maine↗
USGS1988

Foods of juvenile ring-necked ducks: Relationship to wetland pH

Foods of 37 juvenile ring-necked ducks ( Aythya collaris ) from 16 different wetlands were examined in eastcentral Maine in 1983-85. Invertebrates made up 70% aggregate dry weight (100% occurrence) of the foods of Class Ia-IIa ( ≤ 24 days old) ducklings and 32% (86% occurrence) of Class IIb-III ( ≥ 25 days old) ducklings. These percentages may be as high as 85% for Ia-IIa ducklings and 47% for IIb-III ducklings after adjusting for insect sclerites. Ducklings ate invertebrates from 44 taxa and seeds or fibers from 23 plant taxa. Freshwater sponges (Porifera) were the most important invertebrate and constituted 23% of the foods of all ducklings. Seeds of pondweeds ( Potamogeton spp.) were the most important plant foods. Diets of ducklings from high-pH ( ≥ 6.1) wetlands were more diverse (t = 2.54, P = 0.021) than those from low-pH (<6.1) wetlands and consisted of 33 invertebrate taxa. Only 17 taxa occurred in ducklings from low-pH ponds. Class Ia-IIa ducklings from high-pH wetlands ate more invertebrates (77%) than ducklings from lower-pH wetlands (61%), although the difference was not significant (P = 0.21). Sponges made up the largest percentage of the diets and occurred in similar amounts in high- (34%) and low- (31.5%) pH wetlands.

Maine↗
USGS1988

The effects of hunting on survival rates of American black ducks

Using data from 10 preseason and 10 winter major reference areas from 1950-83, the authors tested hypotheses regarding the effects of hunting on the survival and recovery rates of the American black duck ( Anas rubripes ). Although estimates of the proportion of total annual mortality due to hunting are low (35% for ad and 45% for young) compared to Blandin's (1982) estimates, mean mortality and kill rates have increased since 1982. When hunting regulations were liberalized, recovery rates increased and survival rates decreased in males whereas only recovery rates increased in females. Changes in hunting regulations appeared to affect survival rates of adult males and young American black ducks.

Journal of Wildlife Management↗