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At least 1,009 records · Page 56Linked to original sources
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↗
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↗
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

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↗