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USGS1992

Annual survival rates of adult and immature eastern population tundra swans

Tundra swans ( Cygnus columbianus) of the eastern population were neckbanded in Maryland, North Carolina, and Alaska from 1966 through 1990. These swans were resighted and recaptured during autumn, winter, and spring, 1966-1990. Although the original motivation for this study involved swan movements, we wanted to use the resulting data to test hypotheses about sources of variation in swan survival rates. Recaptures of legbanded and neckbanded swans permitted us to estimate neckband loss rates, which were found to vary with age and sex of swans, and number of years since initial application. Estimates of annual neckband retention rate ranged from about 0.50 for adult male swans ≥ 2 years after initial neckbanding to > 0.96 for immature swans and adult females the first year following neckbanding. This variation in neckband loss rates prevented the simple correction of survival estimates to account for such loss. Consequently, we developed a series of multinomial models parameterized with survival, sighting, and neckband retention probabilities for use with the recapture and resighting data.

Alaska, Maryland, North Carolina↗
USGS1992

Band reporting rates of mallards in the Mississippi alluvial valley

We captured 2,182 mallards ( Anas platyrhynchos ) in eastcentral Arkansas and marked 730 with standard bands, 728 with 10 reward bands, and 724 with 'dummy' radio transmitters during November 1986-89 to estimate band reporting rates in the Mississippi Alluvial Valley (MAV). Assuming all transmitters were reported, reporting rates were 0.16 (SE=0.049) for standard bands and 0.34 (SE=0.081) for 10 reward bands. Interviews with hunters indicated that flock size distributions differed ( P =0.03) between mallards wearing transmitters and those wearing bands (standard or reward). Mallards wearing transmitters were more likely to be alone and less likely to be in large flocks when recovered than were mallards wearing bands. These results suggest that either band reporting rates of mallards in the MAV are substantially less than those of midcontinent mallards ( P =0.03), or marking mallards with external transmitters increases susceptibility to hunting mortality.

Arkansas↗
USGS1990

Survival of Mallard broods in Benton Lake National Wildlife Refuge in north central Montana

We estimated duckling survival in broods of 31 radio-marked female mallards ( Anas platyrhynchos ) on Benton Lake National Wildlife Refuge (NWR) in northcentral Montana in 1985 and 1986. Overall survival for the 60-day prefledging period was 0.3951, and 87% of all duckling losses occurred within the first 18 days. Survival through the Class I interval (0.4664) was lower (P < 0.05) than through Class II (0.8887) and Class III (0.9531). Total brood loss occurred among 37% of the females and accounted for 60% of all duckling losses. Broods that survived to fledging averaged 5.0 ducklings. The 60-day survival probability (0.4417) of ducklings in broods that hatched early (on or before 10 Jun) was higher (P < 0.05) than survival of late broods (0.3324). Apparent brood size did not differ (P > 0.05) between marked and unmarked adult females.

Montana↗
USGS1990

Decline of wildcelery buds in the lower Detroit River, 1950-85

American wildcelery buds (Vallisneria americana), an abundant food eaten by diving ducks (Aythini) during migrations, decreased in the lower Detroit River of the Great Lakes from 1950 to 1985. Bud densities decreased at 2 (-14 and -18 buds/mA?) of 5 locations and were similar at 3 (-2, +2, and +3 buds/mA?) of 5 locations. Net change in all 5 areas combined, however, was a decrease of 36,720,000 buds, a 72% decline. Estimated potential losses of waterfowl feeding days caused by the decreased bud densities were 147,000 for canvasbacks (Aythya valisineria), 241,000 for redhead ducks (A. americana), or 664,000 for lesser scaup (A. affinis). Thus, the decline of wildcelery in the Detroit River may have contributed to decreased use of Michigan migration routes by some waterfowl species between 1950 and 1985.

Journal of Wildlife Management↗
USGS1990

Habitat relationships and nest site characteristics of cavity-nesting birds in cottonwood floodplains

We examined habitat relationships and nest site characteristics for 6 species of cavity-nesting birds--American kestrel ( Falco sparverius ), northern flicker ( Colaptes auratus ), red-headed woodpecker ( Melanerpes erythrocephalus ), black-capped chickadee ( Parus atricapillus ), house wren ( Troglodytes aedon ), and European starling ( Sturnus vulgaris )--in a mature plains cottonwood ( Populus sargentii ) bottomland along the South Platte River in northeastern Colorado in 1985 and 1986. We examined characteristics of cavities, nest trees, and the habitat surrounding nest trees. Density of large trees (>69 cm dbh), total length of dead limbs ≥10 cm diameter (TDLL), and cavity density were the most important habitat variables; dead limb length (DLL), dbh, and species were the most important tree variables; and cavity height, cavity entrance diameter, and substrate condition at the cavity (live vs. dead) were the most important cavity variables in segregating cavity nesters along habitat, tree, and cavity dimensions, respectively. Random sites differed most from cavity-nesting bird sites on the basis of dbh, DLL, limb tree density (trees with ≥1 m dead limbs ≥10 cm diameter), and cavity density. Habitats of red-headed woodpeckers and American kestrels were the most unique, differing most from random sites. Based on current trends in cottonwood demography, densities of cavity-nesting birds will probably decline gradually along the South Platte River, paralleling a decline in DLL, limb tree density, snag density, and the concurrent lack of cottonwood regeneration.

Journal of Wildlife Management↗
USGS1990

Effects of tillage practices and carbofuran exposure on small mammals

We compared population estimates, body mass, movement, and blood chemistry of small mammals between conventionally tilled and no-till cornfields in Maryland and Pennsylvania to evaluate the effects of tillage practices and carbofuran exposure on small mammals. Estimates suggest that populations of white-footed mice ( Peromyscus leucopus ) were not significantly related (P > 0.05) to tillage practice or to the presence of winter rye cover crops. Late summer differences in animal mass and movement, and in the proportion of reproductively inactive animals imply that characteristics of individuals and reproductive activity can be affected by tillage practices and winter cover crops. The presence of granular carbofuran had no apparent effect on populations, body mass, or movement in conventionally tilled or no-till fields. Similarly, neither red blood cell acetylcholinesterase, hematocrit, nor liver function were affected by carbofuran use.

Maryland, Pennsylvania↗
USGS1995

Evaluating growth of the Porcupine Caribou Herd using a stochastic model

Estimates of the relative effects of demographic parameters on population rates of change, and of the level of natural variation in these parameters, are necessary to address potential effects of perturbations on populations. We used a stochastic model, based on survival and reproduction estimates of the Porcupine Caribou (Rangifer tarandus granti) Herd (PCH), during 1983-89 and 1989-92 to obtain distributions of potential population rates of change (r). The distribution of r produced by 1,000 trajectories of our simulation model (1983-89, r̄ = 0.013; 1989-92, r̄ = 0.003) encompassed the rate of increase calculated from an independent series of photo-survey data over the same years (1983-89, r = 0.048; 1989-92, r = -0.035). Changes in adult female survival had the largest effect on r, followed by changes in calf survival. We hypothesized that petroleum development on calving grounds, or changes in calving and post-calving habitats due to global climate change, would affect model input parameters. A decline in annual adult female survival from 0.871 to 0.847, or a decline in annual calf survival from 0.518 to 0.472, would be sufficient to cause a declining population, if all other input estimates remained the same. We then used these lower survival rates, in conjunction with our estimated amount of among-year variation, to determine a range of resulting population trajectories. Stochastic models can be used to better understand dynamics of populations, optimize sampling investment, and evaluate potential effects of various factors on population growth.

Alaska↗
USGS1991

Historical changes in laying date, clutch size, and nest success of American black ducks

The breeding population of American black ducks ( Anas rubripes ) on Chesapeake Bay has declined over the past 30 years. We tested whether there have been changes in laying date, clutch size, and nest success of breeding black ducks on islands in Chesapeake Bay between the 1950's and 1980's. None of these variables differed significantly between decades, suggesting that other factors must be responsible for the decline in locally breeding black ducks.

Maryland, Virginia↗
USGS1991

Changes in mallard breeding populations in relation to production and harvest rates

We used breeding population, band recovery, and hunter harvest data to examine whether rates of productivity and harvest correlated with annual changes in mallard ( Anas platyrhynchos ) breeding populations. Percent change in the size of the breeding population correlated positively with an index of production rate and negatively with an index of harvest rate ( R 2 = 0.37, F = 8.34, P < 0.005). Average harvest rate indices did not differ ( W = 126, P < 0.32) between periods of increasing (1961-69) and decreasing (1970-85) populations. Indices to production tended to be lower ( W = 143, P < 0.08) during 1970-85 ( x̄ = 0.064) compared to 1961-69 ( x̄ = 1.096).

Journal of Wildlife Management↗
USGS1993

Autumn diet of lesser snow geese staging in northeastern Alaska

The coastal plain of the Arctic National Wildlife Refuge (ANWR) is used by lesser snow geese ( Chen caerulescens caerulescens ) in autumn for premigratory staging. To better understand the potential impacts of human disturbance on snow geese, we investigated species composition of, and temporal and age-related variation in, their diet during staging. Depending on age and time of collection, between 35.2 and 94.1% of the diet (aggregate percent wet mass, n = 75) consisted of 2 species of plants; underground stems of tall cotton-grass ( Eriophorum angustifolium ), and aerial shoots of northern scouring rush ( Equisetum variegatum ). The diet varied between August and September ( P = 0.0089), morning and afternoon ( P < 0.0001), but not between age classes ( P = 0.066). Throughout staging, snow geese consumed more tall cotton-grass during the afternoon than during the morning ( P < 0.05). Tall cotton-grass was a larger component of the afternoon diet in September than in August ( P < 0.05). In September, snow geese consumed more northern scouring rush in the mornings than in the afternoon ( P < 0.05). Nighttime freezing, interspecific differences in nutritional quality, and plant senescence likely constrained the diet of snow geese to a small number of food items. Because alternative foods may not be available, human disturbance should be minimized in areas that provide these forage species.

Alaska↗
USGS1990

Estimation of confidence intervals for federal waterfowl harvest surveys

I developed methods of estimating confidence intervals for the federal waterfowl harvest surveys conducted by the U.S. Fish and Wildlife Service (USFWS). I estimated flyway harvest confidence intervals for mallards ( Anas platyrhynchos ) (95% CI are ± 8% of the estimate). Canada geese ( Branta canadensis ) ( ± 11%), black ducks ( Anas rubripes ) ( ± 16%), canvasbacks ( Aythya valisineria ) ( ± 32%), snow geese ( Chen caerulescens ) ( ± 43%), and brant ( Branta bernicla ) ( ± 46%). Differences between annual estimate of 10, 13, 22, 42, 43, and 58% could be detected with mallards, Canada geese, black ducks, canvasbacks, snow geese, and brant, respectively. Estimated confidence intervals for state harvests tended to be much larger than those for the flyway estimates.

Journal of Wildlife Management↗
USGS1990

North-south gradient in survival rates in midcontinental populations of mallards

I used band recovery data to test for the existence of a north-south gradient in survival and recovery rates for midcontinental populations of mallards ( Anas platyrhynchos ) during 3 time periods (1962-70, 1971-78, 1979-84). Mean annual survival rates for adult males and females were significantly associated with mean banding latitude (P < 0.0001 and P < 0.0004, respectively) and time period (P < 0.0001 and P < 0.001, respectively). Survival rates for both adult males and females were higher in the north and lower in the south. Because individuals from the northern regions migrate farther, the cost of migration in terms of survival was lower than some other factor(s) that may cause the gradient. The relationship between mean banding latitude and mean annual recovery rates was marginally significant for adult males (P = 0.043) but not for adult females (P = 0.183), suggesting that the gradient was not due to differential harvest pressure. At present, the north-south gradient in survival rates cannot be explained but may be caused by similar north-south clines in predation, habitat degradation, land use, and/or agricultural practices.

Journal of Wildlife Management↗
USGS1990

Influence of ingested lead on body mass of wintering canvasbacks

We determined the prevalence of lead shotgun pellets in gizzards of canvasbacks ( Aythya valisineria ) collected at Catahoula Lake and the Mississippi River Delta, Louisiana, during winter 1987-88 to assess the influence of ingested lead shot on canvasback body mass. The prevalence of ingested lead shot was significantly higher at Catahoula Lake (27%) than at the Mississippi River Delta (4%). Canvasbacks collected at Catahoula Lake showed significant differences in prevalence of ingested lead shot by age and month. We attributed age-related and seasonal variations to differences in foraging effort and exposure time. Body mass of canvasbacks at Catahoula Lake, after accounting for age, monthly variation, and body size, was significantly reduced (120 g or 10%) in birds that had lead shot in their gizzards.

Louisiana↗
USGS1990

An evaluation of techniques to measure contour feather molt in ducks

We evaluated 3 techniques (air jet, flat skin, grab sample) to assess molt in dead waterfowl (green- winged teal [ Anas crecca ] and king eider [ Somateria spectabilis ]). The air jet technique was fast and required no specimen preparation. The flat skin technique required lengthy preparation time after which molt was assessed quickly. Both techniques underestimated the extent of molt (P < 0.01). The grab sample technique needed no preparation but involved time-consuming counting to obtain the molt assessment. The grab sample was preferred when study skins did not need to be preserved because it was easy to conduct, and it was repeatable and more accurate than the other techniques.

California↗
USGS1990

Conditioning of sandhill cranes during fall migration

Body mass of adult female and male sandhill cranes (Grus canadensis) increased an average of 17 and 20%, respectively, from early September to late October on staging areas in central North Dakota and varied by year. Increases in body mass averaged 550 and 681 g among female and male G. c. canadensis, respectively, and 616 and 836 g among female and male G. c. rowani. Adult and juvenile G. c. rowani were lean at arrival, averaging 177 and 83 g of fat, respectively, and fat reserves increased to 677 and 482 g by mid-October. Fat-free dry mass increased by 12% among juveniles, reflecting substantial growth, but remained constant among adults. The importance of fall staging areas as conditioning sites for sandhill cranes, annual variation in body mass, and vulnerability of cranes to habitat loss underscore the need to monitor status of fall staging habitat in the northern plains region and to take steps to maintain suitable habitat where necessary.

Journal of Wildlife Management↗
USGS1990

Field testing of commercially manufactured capture collars on white-tailed deer

We conducted 31 tests of commercially manufactured capture collars on female white-tailed deer ( Odocoileus virginianus ) in the Superior National Forest, Minnesota, under temperatures from -37C to 22C. Deer were recaptured in 28 of the 31 tests; in the 3 failures, we remotely released the collars from the deer. Communication with the collars was achieved from up to 3.0 km on the ground and 26.5 km from the air.

Minnesota↗
USGS1990

Minimizing capture-related stress on white-tailed deer with a capture collar

We compared the effect of 3 capture methods for white-tailed deer ( Odocoileus virginianus ) on blood indicators of acute excitement and stress from 1 February to 20 April 1989. Eleven adult females were captured by Clover trap or cannon net between 1 February and 9 April 1989 in northeastern Minnesota. These deer were fitted with radio-controlled capture collars, and 9 deer were recaptured 7-33 days later. Trapping method affected serum cortisol (P < 0.0001), hemoglobin (Hb) (P < 0.06), and packed cell volume (PCV) (P < 0.07). Cortisol concentrations were lower (P < 0.0001) in capture-collared deer (0.54 ± 0.07 [SE] μg/dL) compared to Clover-trapped (4.37 ± 0.69 μg/dL) and cannon-netted (3.88 ± 0.82 μg/dL) deer. Capture-collared deer were minimally stressed compared to deer captured by traditional methods. Use of the capture collar should permit more accurate interpretation of blood profiles of deer for assessement of condition and general health.

Minnesota↗