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USGS2018

Land management alters traditional nutritional benefits of migration for elk

Ungulates typically migrate to maximize nutritional intake when forage varies seasonally. In western North America, however, increasing numbers of ungulates reside on low-elevation winter range year-round rather than migrating. These residents often occupy irrigated agricultural areas, but it is not known whether the nutrition provided by agricultural land exceeds that gained by migration. We evaluated the nutrition available to a partially migratory population of elk ( Cervus canadensis ) in west-central Montana where some individuals summered on low-elevation agricultural lands, whereas others summered on traditional higher-elevation ranges. We sampled elk forage plants from ground plots and adult female elk movements from global positioning system (GPS) collar locations during late summer for 2 years. We tested for differences in the nutrition provided by 11 vegetative communities commonly available to elk in the Rocky Mountains and the nutrition available in areas used by individuals whose behaviors ranged from residency to migration. We found the nutrition available to elk decreased along the continuum from resident to migratory behavior, contrary to our hypothesis that all behaviors would provide access to equivalent forage quality. The relatively small summer home ranges of migrants suggest other factors (e.g., decreased competition) may compensate for their lower nutritional value, because the size of a home range is often inversely related to its fitness benefits. We found irrigated agriculture provided the highest forage quality in low elevations, but recently burned (1–6 yr prior) dry forests at higher elevations provided forage quality approximately equivalent to that of irrigated agriculture. Excluding elk from irrigated agricultural areas should therefore reduce nutritional incentives for elk to reside at low elevations year-round. Additionally, fire in higher-elevation dry forests may temporarily increase forage quality for elk and improve nutritional benefits of migratory behavior. Our results indicate land management practices can affect nutritionally mediated fitness benefits of differing behaviors in partially migratory populations of ungulates

Montana↗

USGS2013

Geographic variation in migration chronology and winter distribution of midcontinent greater white-fronted geese

We evaluated spatial and temporal differences in migratory behavior among different breeding groups of midcontinent greater white-fronted geese (Anser albifrons) using band-recovery data and observations of neck collared geese during migration and winter. Birds from different breeding areas were initially delineated by geographic distance into 6 banding reference areas (BRAs): 1) interior Alaska, 2) North Slope of Alaska, 3) western Northwest Territories (NWT), 4) western Nunavut, 5) central Nunavut, and 6) eastern Nunavut. The banding groups also differed by breeding habitat, with geese from interior Alaska nesting in the boreal forest (taiga), and all other groups breeding in tundra habitats. Geese from interior Alaska migrated earlier during autumn, and were more likely to winter farther south (in Mexico) than geese from other breeding areas. Geese banded in central and eastern Nunavut (Queen Maud Gulf and Inglis River) wintered farther east (in Louisiana) than geese from other breeding areas. Small-scale (within-state) geographic segregation of wintering flocks was evidenced by the recent (post-1990) nearly exclusive use of a new wintering area in north central Texas by geese from interior Alaska. Segregation among BRAs was also apparent in Mexico, where taiga geese were found predominantly in the central Highlands (states of Zacatecas and Durango), whereas tundra geese mostly used states along the Gulf Coast (primarily Tamaulipas). Interior Alaska birds initiated spring migration earlier than geese from other areas, and were more likely than others to stop in the Rainwater Basin of Nebraska, a region where cholera outbreaks periodically kill thousands of geese. Geese from interior Alaska were the first to arrive at spring staging areas in prairie Canada where BRAs exhibited spatial delineation (a longitudinal cline) in relation to breeding areas. Our results show significant geographic and temporal variation among taiga and tundra breeding cohorts during autumn, winter, and spring. Temporal and spatial differences in migratory behavior may allow management practices that accommodate potential demographic differences between taiga and tundra populations.

Journal of Wildlife Management↗

USGS2010

Pintail and mallard survival in California relative to habitat, abundance, and hunting

The influence of habitat, waterfowl abundance, and hunting on winter survival of waterfowl is not well understood. We studied late August-March survival of 163 after-hatch-year (AHY) and 128 hatch-year (HY) female mallards (Anas platyrhynchos) radiotagged in Sacramento Valley (SACV) and 885 AHY female northern pintails (A. acuta) radiotagged throughout the Central Valley of California, USA, relative to flooded habitat (HAB), January abundance of each species (JMAL or JPIN), hunter-days (HDY), and a hunting pressure index (HPI) that combined these variables. From EARLY (1987-1994) to LATE (1998-2000), HAB increased 39%, JPIN increased 45%, JMAL increased 53%, HDY increased 21%, duck-hunting season increased from 59 days to 100 days, and the female daily bag limit doubled to 2 for mallards but remained 1 for pintails. Survival (?? SE) was greater during LATE versus EARLY for pintails radiotagged in each region (SACV: 93.2 ?? 2.1% vs. 87.6 ?? 3.0%; Suisun Marsh: 86.6 ?? 3.2% vs. 77.0 ?? 3.7%; San Joaquin Valley: 86.6 ?? 3.1% vs. 76.9 ?? 4.1%) but not for SACV mallards (AHY: 70.6 ?? 7.2% to 74.4 ?? 7.7% vs. 80.1 ?? 7.2% to 82.8 ?? 5.6%; HY: 48.7 ?? 9.1% [1999-2000 only] vs. 63.5 ?? 8.8% to 67.6 ?? 8.0%). Most pintail (72%) and mallard (91%) deaths were from hunting, and lower HPI and higher JPIN or JMAL were associated with reduced mortality. Increased HAB was associated with reduced winter mortality for pintails but not for SACV mallards. Pintail survival rates that we measured were within the range reported for other North American wintering areas, and during LATE were higher than most, even though our study duration was 68-110 days longer. Winter survival rates of SACV mallards were also within the reported range. However, with higher bag limits and longer seasons, mallard survival during LATE was lower than in most other wintering areas, especially during 1999-2000, when high winds on opening weekend resulted in high hunting mortality. Habitat conservation and favorable agriculture practices helped create a Central Valley wintering environment where natural mortality of mallards and pintails was low and survival varied with hunting mortality. We recommend regulations and habitat management that continue to minimize natural mortality while allowing sustainable harvest at a level that helps maintain strong incentive for management of Central Valley waterfowl habitats, including the large portion that is privately owned.

Journal of Wildlife Management↗

USGS2010

Grizzly bear density in Glacier National Park, Montana

We present the first rigorous estimate of grizzly bear ( Ursus arctos ) population density and distribution in and around Glacier National Park (GNP), Montana, USA. We used genetic analysis to identify individual bears from hair samples collected via 2 concurrent sampling methods: 1) systematically distributed, baited, barbed-wire hair traps and 2) unbaited bear rub trees found along trails. We used Huggins closed mixture models in Program MARK to estimate total population size and developed a method to account for heterogeneity caused by unequal access to rub trees. We corrected our estimate for lack of geographic closure using a new method that utilizes information from radiocollared bears and the distribution of bears captured with DNA sampling. Adjusted for closure, the average number of grizzly bears in our study area was 240.7 (95% CI = 202–303) in 1998 and 240.6 (95% CI = 205–304) in 2000. Average grizzly bear density was 30 bears/1,000 km 2 , with 2.4 times more bears detected per hair trap inside than outside GNP. We provide baseline information important for managing one of the few remaining populations of grizzlies in the contiguous United States.

Montana↗

USGS2010

Winter distribution, movements, and annual survival of radiomarked Vancouver Canada geese in southeast Alaska

Management of Pacific Flyway Canada geese ( Branta canadensis ) requires information on winter distribution of different populations. Recoveries of tarsus bands from Vancouver Canada geese ( B. canadensis fulva ) marked in southeast Alaska, USA, ≥4 decades ago suggested that ≥83% of the population was non-migratory and that annual adult survival was high (Ŝ = 0.836). However, recovery distribution of tarsus bands was potentially biased due to geographic differences in harvest intensity in the Pacific Flyway. Also, winter distribution of Vancouver Canada geese could have shifted since the 1960s, as has occurred for some other populations of Canada geese. Because winter distribution and annual survival of this population had not recently been evaluated, we surgically implanted very high frequency radiotransmitters in 166 adult female Canada geese in southeast Alaska. We captured Vancouver Canada geese during molt at 2 sites where adults with goslings were present (breeding areas) and 2 sites where we observed nonbreeding birds only. During winter radiotracking flights in southeast Alaska, we detected 98% of 85 females marked at breeding areas and 83% of 70 females marked at nonbreeding sites, excluding 11 females that died prior to the onset of winter radiotracking. We detected no radiomarked females in coastal British Columbia, or western Washington and Oregon, USA. Most (70%) females moved ≤30 km between November and March. Our model-averaged estimate of annual survival (Ŝ = 0.844, SE = 0.050) was similar to the estimate of annual survival of geese marked from 1956 to 1960. Likely <2% of Vancouver Canada geese that nest in southeast Alaska migrate to winter areas in Oregon or Washington where they could intermix with Canada geese from other populations in the Pacific Flyway. Because annual survival of adult Vancouver Canada geese was high and showed evidence of long-term consistency, managers should examine how reproductive success and recruitment may affect the population.

Alaska↗

USGS1984

Habitat use by migrant sandhill cranes in Nebraska

The principal spring staging areas of the midcontinent population of sandhill cranes ( Grus canadensis ) are along the Platte and North Platte rivers in south-central Nebraska. Most of these lands are privately owned and managed for corn and cattle production. Diurnal habitat use by radio-tagged cranes was primarily in cropland (55%), native grassland (28%), and tame hayland (15%). Ninety-nine percent of the cropland use was in cornfields; 55% as grazed stubble, 36% as disced, cultivated, and plowed stubble, 7% as ungrazed stubble, and 1% unclassified. Grazed pastures accounted for 93% of the grassland locations and mowed alfalfa fields 77% of the tame hayland locations. Other habitats were seldom used. Time budget analyses indicated that cranes, while in croplands, grasslands, and haylands, spent 35, 36, and 50% of the time foraging, respectively. Cranes roosted in the shallows and on nearby sandbars of about 111 km of river channel. Cranes usually roosted where the channel was at least 150 m wide and avoided stretches narrower than 50 m. Height of woody vegetation along shorelines and on islands influenced where cranes roosted when unobstructed channel width was less than 150 m; bridges or roads adjacent to the channel also reduced use by about half. Management recommendations are made for maintaining suitable habitat for sandhill cranes on their staging areas in Nebraska.

Nebraska↗

USGS2003

Factors affecting gadwall brood and duckling survival in prairie pothole landscapes

Waterfowl biologists need reliable predictors of brood and duckling survival to accurately estimate recruitment rates. We examined 30-day survival rates of gadwall (Anas strepera) broods (1992-1994) and ducklings (1990-1994) in eastern North Dakota, USA, during years when water conditions ranged from extremely dry to extremely wet. We evaluated effects of several variables on brood survival : (1) percent of seasonal wetland basins containing water, (2) occurrence of rain on the current or 2 previous exposure days, (3) minimum ambient temperature averaged over the current and 2 previous exposure days, (4) hatch date, (5) duckling age, and (6) brood size. Only 9 of 58 radiomarked females lost their entire broods; Kaplan-Meier 30-day survival rate for broods was 0.84. Brood size (adjusted for hatch date) was a better brood - survival predictor than were any of the environmental variables. Risk of total brood loss decreased by 24% for each additional duckling in the brood . We monitored fates of 212 radiomarked ducklings from 94 broods. Daily risk of death for ducklings was twice as high when seasonal ponds were scarce as when ponds were abundant. Duckling survival rate was lower during the first 7 days of life whether it rained or not; survival rate was greater for 8- to 30-day-old ducklings, but was reduced by rain. Thirty-day duckling survival was greatest when minimum daily temperatures exceeded 10°C and no rain occurred. We attributed 86% of 87 deaths of radiomarked ducklings to predation; American mink (Mustela vison) accounted for ≥68% of the 40 deaths for which predator type could be ascertained. Despite apparent resilience of gadwall populations during drought, our study documented a positive effect of seasonal wetland availability on gadwall duckling survival . Management efforts to improve recruitment will be more effective in years when most seasonal basins contain water.

Minnesota↗

USGS1995

Spring-summer survival rates of yearling versus adult mallard females

Knowledge of the timing, magnitude, and cause of mortality in wildlife populations is imperative for developing management strategies that protect or improve the status of these populations. Age- and sex-specific population parameter estimates provide the most useful information for this purpose. Numerous studies have provided information about survival rates in mallards ( Anas platyrhynchos ), but little is known about age-related differences in female survival during the breeding period. We examined band-recovery data for female mallards banded in southern portions of Alberta, Saskatchewan, and Manitoba during spring and summer 1981-85. We used band-recovery models to test the hypothesis that yearling females would exhibit higher survival compared with that of older females during spring-summer. There was evidence ( P = 0.08) that spring-summer survival rates of yearling females (0.728) were higher than that of older females (0.574). These findings support the hypothesis that age-specific differences in nesting behavior (e.g., later nest initiation and fewer nesting attempts by yearlings) influence losses to predators and are responsible for the difference in spring-summer survival. Management treatments that increase nest success, and consequently reduce the need for prolonged nesting, will increase mallard survival during spring-summer.

Alberta, Manitoba, Saskatchewan↗

USGS2011

Climate change, uncertainty, and natural resource management

Climate change and its associated uncertainties are of concern to natural resource managers. Although aspects of climate change may be novel (e.g., system change and nonstationarity), natural resource managers have long dealt with uncertainties and have developed corresponding approaches to decision-making. Adaptive resource management is an application of structured decision-making for recurrent decision problems with uncertainty, focusing on management objectives, and the reduction of uncertainty over time. We identified 4 types of uncertainty that characterize problems in natural resource management. We examined ways in which climate change is expected to exacerbate these uncertainties, as well as potential approaches to dealing with them. As a case study, we examined North American waterfowl harvest management and considered problems anticipated to result from climate change and potential solutions. Despite challenges expected to accompany the use of adaptive resource management to address problems associated with climate change, we conclude that adaptive resource management approaches will be the methods of choice for managers trying to deal with the uncertainties of climate change. ?? 2010 The Wildlife Society.

Journal of Wildlife Management↗

USGS2010

Yearling greater sage-grouse response to energy development in Wyoming

Sagebrush (Artemisia spp.)-dominated habitats in the western United States have experienced extensive, rapid changes due to development of natural-gas fields, resulting in localized declines of greater sage-grouse (Centrocercus urophasianus) populations. It is unclear whether population declines in natural-gas fields are caused by avoidance or demographic impacts, or the age classes that are most affected. Land and wildlife management agencies need information on how energy developments affect sage-grouse populations to ensure informed land-use decisions are made, effective mitigation measures are identified, and appropriate monitoring programs are implemented (Sawyer et al. 2006). We used information from radio-equipped greater sage-grouse and lek counts to investigate natural-gas development influences on 1) the distribution of, and 2) the probability of recruiting yearling males and females into breeding populations in the Upper Green River Basin of southwestern Wyoming, USA. Yearling males avoided leks near the infrastructure of natural-gas fields when establishing breeding territories; yearling females avoided nesting within 950 m of the infrastructure of natural-gas fields. Additionally, both yearling males and yearling females reared in areas where infrastructure was present had lower annual survival, and yearling males established breeding territories less often, compared to yearlings reared in areas with no infrastructure. Our results supply mechanisms for population-level declines of sage-grouse documented in natural-gas fields, and suggest to land managers that current stipulations on development may not provide management solutions. Managing landscapes so that suitably sized and located regions remain undeveloped may be an effective strategy to sustain greater sage-grouse populations affected by energy developments. ?? 2010 The Wildlife Society.

Journal of Wildlife Management↗

USGS2017

Implementing the 2012 North American Waterfowl Management Plan revision: Populations, habitat, and people

The North American Waterfowl Management Plan (NAWMP) has established a model for wildlife conservation planning over the last 3 decades. Management at a continental scale, leveraged funding, regional partnerships, and a strong science basis have been notable features. Periodic updates to the NAWMP occurred since implementation in 1986; however, a fundamental revision was accomplished in 2012 after extensive stakeholder engagement. An explicit fundamental goal for waterfowl conservation supporters was added in 2012, complementing existing goals for sustainable populations and sufficient habitat found in previous updates. We present a synopsis of progress toward implementation of the 2012 NAWMP and challenge the waterfowl management community to continue with meaningful steps toward achieving NAWMP goals. Adding goals and objectives for supporters increases potential relevance of NAWMP; however, it also presents a level of complexity that was not entirely anticipated. Additionally, the 2012 NAWMP recognized that traditional support from waterfowl hunters alone will not be sufficient to support waterfowl conservation in the future. Simultaneous consideration of multiple objectives, although implicit before, now is a specific focus for habitat and harvest management affecting hunters and other users of the waterfowl resource. The waterfowl management community is faced with revisiting objectives and management actions related to harvest regulations, landscape priorities, habitat conservation, and public engagement to garner broader support. These persistent management challenges are tangible and relevant candidates for greater integration. Ultimately, the structures and processes supporting waterfowl management also will need to be reconsidered.

Journal of Wildlife Management↗

USGS2011

Stopover habitats of spring migrating surf scoters in southeast Alaska

Habitat conditions and nutrient reserve levels during spring migration have been suggested as important factors affecting population declines in waterfowl, emphasizing the need to identify key sites used during spring and understand habitat features and resource availability at stopover sites. We used satellite telemetry to identify stopover sites used by surf scoters migrating through southeast Alaska during spring. We then contrasted habitat features of these sites to those of random sites to determine habitat attributes corresponding to use by migrating scoters. We identified 14 stopover sites based on use by satellite tagged surf scoters from several wintering sites. We identified Lynn Canal as a particularly important stopover site for surf scoters originating throughout the Pacific winter range; approximately half of tagged coastally migrating surf scoters used this site, many for extended periods. Stopover sites were farther from the mainland coast and closer to herring spawn sites than random sites, whereas physical shoreline habitat attributes were generally poor predictors of site use. The geography and resource availability within southeast Alaska provides unique and potentially critical stopover habitat for spring migrating surf scoters. Our work identifies specific sites and habitat resources that deserve conservation and management consideration. Aggregations of birds are vulnerable to human activity impacts such as contaminant spills and resource management decisions. This information is of value to agencies and organizations responsible for emergency response planning, herring fisheries management, and bird and ecosystem conservation.

Journal of Wildlife Management↗

USGS2025

Linking age and social status of cooperative breeders to vulnerability throughout the harvest season

Individual behaviors are influenced by environmental, genetic, and demographic factors. Some animals choose to live in groups and cooperatively breed, and their behaviors can change depending on dynamic factors such as group size and composition that affect group persistence. In Idaho, USA, gray wolves ( Canis lupus ) are harvested annually, providing an opportunity to investigate the effects of harvest and seasonal behaviors on a population of cooperative breeders. These annual hunting and trapping seasons overlap with the dispersal and breeding periods for wolves and we do not know how harvest affects the vulnerability of different sex and age classes during these important biological periods. We applied 9 years (2009–2018) of genetic, age, and harvest data from harvested wolves to investigate how behaviors (dispersal and breeding) and biological drivers might influence the vulnerability of wolves to harvest. We created pedigrees from genotypes of non-invasively collected scats to estimate the expected proportion of the wolf population composed of 3 different age classes (pup, yearling, and sexually mature or ≥2 years old) and compared them to the observed number of each age class harvested during biologically significant periods (i.e., dispersal and breeding). We found that pups were more vulnerable to harvest in December when wolf harvest transitioned largely to trapping (accounts for 66% of harvest), and found evidence that adults were more vulnerable to harvest during their breeding season in January and February. In contrast, we found no difference in the expected versus observed number of wolves ≥2 years old in the harvest during peak dispersal season (December), or in the expected versus observed number of yearlings in the harvest during September and October when pups are mobile and groups of wolves abandon the use of pup-rearing sites. Some age classes were disproportionally harvested during certain periods for specific years, but this was not consistent across all years, suggesting there is more to learn about the vulnerability of different age classes to harvest. We found harvest can disproportionally affect some demographic classes of individuals depending on year, biological period, and harvest type. With wolves continuing to recolonize historical ranges, our approach can benefit managers and future studies with the goal of identifying how interannual harvest affects groups of wolves.

Idaho↗

USGS2025

Exploring the importance of metapopulation dynamics with population control strategies for invasive silver carp in the upper Mississippi River

Invasive bigheaded carps (Bighead Carp Hypophthalmichthys nobilis , Silver Carp Hypophthalmichthys molitrix , and their hybrids Hypophthalmichthys spp.) currently infest the Mississippi River Basin. Bigheaded carps can outcompete native species in invaded waters and can also transform the surrounding environment. Currently, resource managers seek to limit the population abundance of bigheaded carps and their range expansion into additional regions of the Upper Mississippi River (UMR) but lack a tool to evaluate different control strategies. Here, we present an application of a Silver Carp spatial population model in the UMR to fill this gap. We used the model to explore how simulated control strategies could affect Silver Carp metapopulation dynamics. More specifically, we assessed and compared the importance of movement deterrents, removal locations, and recruitment areas on Silver Carp population abundances across the UMR. Strategies that included a combination of removal efforts and deterrents resulted in the largest decreases in Silver Carp abundance in the upper pools of the UMR. Furthermore, scenarios that targeted source populations of Silver Carp rather than sink populations resulted in larger decreases in Silver Carp abundance at the invasion front. The effectiveness of these combined simulated strategies also depended on the location of Silver Carp recruitment. Our work suggests that an understanding of Silver Carp metapopulation dynamics may be important for control efforts and could help to inform the management of Silver Carp in the UMR.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗

USGS2010

Effects of earlier sea ice breakup on survival and population size of polar bears in western Hudson Bay

Some of the most pronounced ecological responses to climatic warming are expected to occur in polar marine regions, where temperature increases have been the greatest and sea ice provides a sensitive mechanism by which climatic conditions affect sympagic (i.e., with ice) species. Population-level effects of climatic change, however, remain difficult to quantify. We used a flexible extension of Cormack-Jolly-Seber capture-recapture models to estimate population size and survival for polar bears (Ursus maritimus), one of the most ice-dependent of Arctic marine mammals. We analyzed data for polar bears captured from 1984 to 2004 along the western coast of Hudson Bay and in the community of Churchill, Manitoba, Canada. The Western Hudson Bay polar bear population declined from 1,194 (95% CI = 1,020-1,368) in 1987 to 935 (95% CI = 794-1,076) in 2004. Total apparent survival of prime-adult polar bears (5-19 yr) was stable for females (0.93; 95% CI = 0.91-0.94) and males (0.90; 95% CI = 0.88-0.91). Survival of juvenile, subadult, and senescent-adult polar bears was correlated with spring sea ice breakup date, which was variable among years and occurred approximately 3 weeks earlier in 2004 than in 1984. We propose that this correlation provides evidence for a causal association between earlier sea ice breakup (due to climatic warming) and decreased polar bear survival. It may also explain why Churchill, like other communities along the western coast of Hudson Bay, has experienced an increase in human-polar bear interactions in recent years. Earlier sea ice breakup may have resulted in a larger number of nutritionally stressed polar bears, which are encroaching on human habitations in search of supplemental food. Because western Hudson Bay is near the southern limit of the species' range, our findings may foreshadow the demographic responses and management challenges that more northerly polar bear populations will experience if climatic warming in the Arctic continues as projected.

Journal of Wildlife Management↗

USGS2010

Proximate cues for a short-distance migratory species: An application of survival analysis

Investigation of bird migration has often highlighted the importance of external factors in determining timing of migration However, little distinction has been made between short- and long-distance migrants and between local and flight birds (passage migrants) in describing migration chronology. In addition, measures of food abundance as a proximate factor influencing timing of migration are lacking in studies of migration chronology. To address the relationship between environmental variables and timing of migration we quantified the relative importance of proximate external factors on migration chronology of local American woodcock (Scolopax minor), a short distance migrant, using event-time analysis methods (survival analysis). We captured 1,094 woodcock local to our study sites in Michigan, Minnesota and Wisconsin (USA) during autumn 2002-2004 and documented 786 departure dates for these birds. Photoperiod appeared to provide an initial proximate cue for timing of departure. Moon phase was important in modifying timing of departure, which may serve as a navigational aid in piloting and possibly orientation. Local synoptic weather variables also contributed to timing of departure by changing the rate of departure from our study sites. We found no evidence that food availability influenced timing of woodcock departure. Our results suggest that woodcock use a conservative photoperiod-controlled strategy with proximate modifiers for timing of migration rather than relying on abundance of their primary food, earthworms. Managing harvest pressure on local birds by adjusting season lengths may be an effective management tool with consistent migration patterns from year to year based on photoperiod.

Journal of Wildlife Management↗

USGS1989

Winter survival of female American black ducks on the Atlantic coast

We used radio telemetry to monitor the winter survival and cause-specific mortality of 227 female American black ducks ( Anas rubripes ) captured in New Jersey and Virginia, 1983-85. Mean survival rate for 19 December-15 February was 0.65. Survival from hunting and nonhunting risk was 0.84 and 0.78, respectively. Causes of nonhunting mortality included predation and emaciation (winter stress). After-hatch-year (AHY) ducks had a higher probability of survival than hatch-year (HY) ducks (0.73 vs. 0.60); most of this difference was related to survival from nonhunting risk. After-hatch-year ducks with body masses > median had a higher survival probability (0.85) than AHY ducks with < median body masses (0.61) because of differential survival from hunting risk. Hatch-year ducks had lower body mass than AHY ducks, but among HY ducks body mass was not related to survival. There were no consistent patterns in survivorship in relation to mean daily temperature, although the timing of the onset of low temperatures and storms may have influenced movement patterns. Our estimated survival rates are consistent with estimates from other studies of seasonal and annual survival. It may be possible to manage habitats for population segments at high risk (HY and low body mass birds), and increase black duck survivorship.

New Jersey, Virginia↗

USGS1998

The use of fields at night by wintering American woodcock

Because limited information is available regarding preferences for nocturnal habitat during winter, we studied use of nocturnal habitats by American woodcock (Scolopax minor) wintering in the Georgia Piedmont (1994-95). During the evening crepuscular period, woodcock on the wintering grounds move from forested to field habitats, presumably to feed, conduct courtship displays, roost, and avoid predators. We conducted crepuscular flight surveys and tracked radiomarked woodcock to compare the use of fields of different sizes (<5.5 ha, 5.5-40.0 ha, >40.0 ha) and types (seed tree-clearcuts, fallow-old fields, hayfields, pastures). Fields ≥5.5 ha were used more frequently than fields <5.5 ha (P < 0.001). Seed tree-clearcuts and fallow-old fields were more frequently used than pastures (P = 0.003). Woodcock also most frequently used fields with greater foliage volume at 0.8-2.0 m in height and a high percentage of bare soil (P < 0.001). Nocturnal use of fields or forests by radiomarked woodcock did not differ among age of sex classes. However, females moved an average of 230 ± 32.1 m (x̄ ± SE) between diurnal and nocturnal locations, while males moved 525 ± 53.1 m (P = 0.085). Movements differed among moon phases (P < 0.003), ranging from 579 ± 79.6 m during the new moon to 213 ± 50.5 m during the full moon. To manage habitat on the wintering grounds, seed tree-clearcuts and fallow-old fields should be created or maintained near preferred diurnal habitats.

Journal of Wildlife Management↗