James K. Ringelman

DUCK NEST SURVIVAL IN THE MISSOURI COTEAU OF NORTH DAKOTA: LANDSCAPE EFFECTS AT MULTIPLE SPATIAL SCALES

Nest survival is one of the most important parameters in the population dynamics of grassland-nesting ducks (Anas and Aythya spp.) that breed in the Prairie Pothole Region of North America. Grassland habitats used by these species are increasingly threatened by habitat loss and the coincident fragmentation, which may indirectly alter nest survival through effects on predators. Although predators are the dominant cause of nest loss, they are difficult to monitor directly. Thus, indirect analyses of habitat variables are required. Many studies have attempted to address the relationship between fragmentation and nest survival; however, few studies have examined the influence of fragmentation at multiple spatial scales. Understanding how landscape characteristics at multiple spatial scales explain variation in nest survival is important, because no single correct scale is likely to exist for a diversity of landscape metrics. We examined the relationships between habitat variables and duck nest survival (n ≈ 4...

Predicting Risk of Habitat Conversion in Native Temperate Grasslands

Native grasslands that support diverse populations of birds are being converted to cropland at an increasing rate in the Prairie Pothole Region of North America. Although limited funding is currently available to mitigate losses, accurate predictions of probability of conversion would increase the efficiency of conservation measures. We studied conversion of native grassland to cropland in the Missouri Coteau region of North and South Dakota (U.S.A.) during 1989-2003. We estimated the probability of conversion of native grassland to cropland with satellite imagery and logistic regression models that predicted risk of conversion and by comparing the overlap between areas of high biological value and areas most vulnerable to conversion. Annualized probability of conversion was 0.004, and 36,540 ha of native grassland were converted to cropland during the period of our study. Our predictive models fit the data and correctly predicted 70% of observed conversions of grassland. Probability of conversion varied spatially and was correlated with landscape features like amount of surrounding grassland, slope, and soil productivity. Tracts of high biological value were not always at high risk of conversion. We concluded the most biologically valuable areas that are most vulnerable to conversion should be prioritized for conservation. This approach can be applied broadly to other systems and offers great utility for implementing conservation in areas with spatially variable biological value and probability of conversion.

DIURNAL VISIBILITY AND ACTIVITY OF BLUE-WINGED TEAL AND MALLARD BROODS1

Activities of blue-winged teal (Anas discors) and mallard (A. 1>latyrhynchos) broods were recorded continuously from sunrise to sunset in South Dakota during 1976. Observations totaling 255 brood-days were evaluated by species and age-class. Morning and evening feeding peaks became more pronounced, and visibility increased, with brood age. Swimming activity decreased, and visihle loaflng, sleeping, and depth of subsurface feeding increased in older broods. Behavior of class-I ducklings was similar in both species. Class-II and -III mallard broods loafed more and fed less in open water than did teal broods of the same age. Wind speeds in excess of 24 kmlhour and air temperatures above 23 C were associated with decreased brood visibility. Recommendations are made for increasing the accuracy and efficiency of brood inventories.

Movements and wetland selection by brood-rearing black ducks

Movements and wetland selection by brood-rearing black ducks (Anas rubripes) were studied in Maine during 1977-80. Eight radio-marked hens moved their broods an average of 1.2 km from the nest to rearing pond, but only 1 hen initiated secondary brood movements. Half of the 85 broods reared in the study area used only 3 wetlands, and most rearing ponds contained active beaver (Castor canadensis) colonies. Brood-rearing hens preferred Emergent ponds over lakes and Evergreen Scrub-Shrub wetlands, and did not occupy Dead Scrub-Shrub, Unconsolidated Bottom, or Aquatic Bed wetlands. Rearing ponds were large and possessed extensive areas of flooded mountain alder (Alnus incana), willow (Salix spp.), and herbaceous vegetation. Wetlands avoided by brood-rearing hens were those with large areas of open water, submergent aquatics, or ericaceous shrub vegetation. J. WILDL. MANAGE. 46(3):615-621 The ability of female black ducks to select brood-rearing ponds that will fulfill the changing food and habitat requirements of growing ducklings increases the prospects for brood survival. Many researchers (V. D. Stotts, unpubl. rep., Maryland Game and Inland Fish Comm., Fed. Aid Proj. W-30-R-7, 1959; Reed 1970; Hepp and Hair 1977) have recognized the importance of rearing areas and have identified the types of wetlands used by black duck broods. However, comparatively little is known about the wetland habitat components that serve as proximate factors (Hilden 1965) in the selection process. Studies of primary and secondary brood movements (Evans et al. 1952, Berg 1956, Stewart 1958, Beard 1964, Ball 1973) indicate that ducks actively select rearing areas. Wright (1954) observed a black duck hen leading her brood >3.2 km overland to a rearing area, and Young (1967) discussed the overland movements of 2 broods to a large pond >1.6 km away. Detailed data on brood movements of inland-nesting black ducks have been unavailable, but are necessary for an understanding of duckling survival and habitat selection. We investigated the selection of wetlands and habitat components by radio-marked and unmarked female black ducks, and the movements of marked, brood-rearing hens. We acknowledge the work of field assistants J. M. Connolly, J. D. Schoultz, J. Sease, and S. E. Staples. T. J. Dwyer, L. D. Flake, and G. M. Haramis provided comments on early drafts of the manuscript. Financial support for this study was provided in part by contract #14-160008-2125 from the Migratory Bird and Habitat Research Laboratory, U.S. Fish and Wildlife Service, and by the School of Forest Resources, University of Maine, Orono. STUDY AREA AND METHODS The 151-km2 study area was 30 km southwest of Bangor, Maine in the northern hardwoods-spruce ecoregion (Bailey 1978). Forty-four of the 118 study wetlands were created or modified by beaver. Most ponds were classified as EverI Present address: Colorado Division of Wildlife, Research Center, 317 W. Prospect, Fort Collins, CO 80526. J. Wildl. Manage. 46(3):1982 615 This content downloaded from 157.55.39.147 on Sun, 07 Aug 2016 07:03:12 UTC All use subject to http://about.jstor.org/terms 616 BROOD-REARING BLACK DUCKS* Ringelman and Longcore green or Deciduous Scrub-Shrub, Deciduous Forested, or Persistent Emergent wetland types (Cowardin et al. 1979), and ranged in size from 0.1 to 64.2 ha. A detailed description of the study area was presented by Ringelman (1980:3). Data on brood movements were attained by following radio-marked females which were captured before brood-rearing with nest traps (Coulter 1958) or rocket nets. Females were instrumented with 25-g, back-mounted transmitters and monitored 2-3 times per day with a mobile, null-peak tracking system using conventional telemetry techniques. Observations of unmarked broods, supplemented with telemetry records of radio-marked hens, provided data that were used in the analysis of habitat selection. Rearing ponds were defined as wetlands used by a brood for >24 hours. Brood surveys were conducted on all rearing ponds every 6-10 days from the last week in May through the end of July 1977-80. Most observations were made from tree stands 3-15 m above the waters surface. Black duck broods were characterized by number and age of ducklings (J. B. Gollop and W. H. Marshall, unpubl. rep., Miss. Flyway Tech. Sect., 1954), because a unique combination of these characteristics enabled us to re-identify individual broods during subsequent visits. Details of our brood survey methods are described elsewhere (Longcore and Ringelman 1980). The hypothesis that brood use differed significantly from the availability of each wetland class was tested with a z statistic (Neu et al. 1974). A stepwise forward discriminant analysis (Klecka 1975) was performed to identify individual habitat components characteristic of wetlands used vs. those avoided by broods. Twenty-eight habitat components (Table 1) were used as discriminating variables. Preliminary analyses indicated that variable means were proportional to standard deviations, so a logarithmic transformation (log[x + 1]) was applied to all data (Zar 1974:184) to avoid problems created by heteroscedasticity and non-normality (Box and Cox 1964, Eisenbeis and Avery 1972).

Time-lagged variation in pond density and primary productivity affects duck nest survival in the Prairie Pothole Region

The Prairie Pothole Region (PPR) is the primary breeding region for most species of North American dabbling ducks (Anas spp.). Conservation of these species is guided in part by knowledge of relationships between nest survival probability and habitat features. Positive relationships between duck nest survival and amount and configuration of herbaceous perennial vegetation have been observed in previous studies, but these 2- to 4-year studies might not have adequately characterized the temporal effect of wet-dry episodes on nest survival. Over an eight-year period, we studied nest survival of five species of ducks in the PPR relative to spatial and temporal variation in pond density, primary productivity, and hydrologic status of wetlands, soil, and vegetation on 52 study sites selected to span a gradient of spatial variation in proportion of herbaceous perennial vegetation and in number of wetland basins. We observed the fate of 12 754 nests. Consistent with past studies, 90% of nests that failed to hatch were destroyed by predators. Nest survival probability was positively related to current-year pond density and primary productivity, negatively related to pond density and primary productivity during the previous two years, and positively related to the number of wetland basins on the study site. Predicted relationships between nest survival and proportion or configuration of herbaceous perennial vegetation in the surrounding landscape were not supported. For mallard (Anas platyrhynchos), median estimated nest survival probability ranged from 0.02 (SE = 0.01) to 0.22 (SE = 0.02). Estimated nest survival was greatest on sites with numerous wetland basins that had transitioned from dry, unproductive conditions to wet, productive conditions in the previous 1-2 years. Our results were consistent with time-lagged responses of food webs to resource pulses in a broad array of ecosystems. Our study highlighted the importance of wetland basins and wet-dry episodes to duck nest survival in the PPR. Current habitat conservation efforts focus on landscapes with numerous wetland basins and a high proportion of herbaceous perennial vegetation. Our results suggest that future conservation efforts should focus on preserving high-density wetland complexes across as large a geographic extent as possible even in cropland-dominated landscapes.

EFFECTS OF EMBEDDED TUNGSTEN-BISMUTH-TIN SHOT AND STEEL SHOT ON MALLARDS (ANAS PLATYRHYNCHOS)

We assessed the potential for embedded steel and tungsten-bismuth-tin (TBT) shot to adversely affect health of mallards (Anas platyrhynchos). Ducks were implanted with three number four steel (n = 19) or TBT (n = 20) shot pellets in their pectoral muscles. None of seven hematology parameters measured differed in response to treatment (P ≥ 0.17). At necropsy 1, 2, 4, and 8 wk posttreatment, we observed only localized tissue reactions to embedded steel or TBT shot. Reactions differed grossly: after wk 1, embedded steel shot were enveloped in 0.5 to 2 mm grayish capsules, whereas TBT shot were surrounded by thinner (<0.5 mm), translucent capsules. Corrosion of steel shot was apparent. Microscopic lesions associated with steel shot were characterized by moderate to severe histiocytic and lymphocytic inflammation and considerable particle deposition, whereas histiocytic inflammation was mild and particle deposition minimal in TBT lesions. Overall scores of inflammation at steel shot implant sites were greater (P ≤ 0.043) than at TBT sites during wk 1 and 8. Inflammation at steel implant sites was relatively consistent over the 8-wk period, but decreased (P = 0.0017) at TBT sites by wk 8. Weights of steel shot recovered from muscle tissue declined logarithmically (R2 = 0.978, P = 0.0014) over 8 wk, but TBT shot weights remained unchanged (P = 0.255). Embedded TBT shot, as compared to steel, resisted corrosion and induced comparatively mild inflammatory responses in mallard muscle tissue. However, inflammatory reactions to both embedded steel and TBT shot were localized and had no detectable systemic effects on mallard health under experimental conditions.

Relationship of Body Condition to Survival of Mallards in San Luis Valley, Colorado

Because body condition can influence survival probabilities in waterfowl, our objective was to determine if winter body condition was related to survival of mallards (Anas platyrhynchos). We obtained body mass and condition indices from mallards captured in southern Colorado from December through March 1986-87, 1987-88, and 1988-89. We collected waterfowl carcasses and wings from January through April 1987-89. In 1987, 1988, and 1989, we recovered 229, 4,193, and 1,663 mallard carcasses, respectively. Avian cholera (Pasteurella multocida), a source of mortality in all years, was prevalent in 1988. Starvation (ulna lipid levels <5%) was more prevalent (P < 0.01) among banded mallards than among unbanded mallards. We used logistic regression to assess relationships between condition at time of banding and whether a bird was found dead within 4 months after capture, shot by hunters the subsequent fall, recaptured 1 year later, or of unknown fate. In 1987, there was a relationship between recaptures and condition (P = 0.03), but no relationship between other status categories and condition. There were no relationships between status and condition in 1988. In 1989, only band recoveries from birds found dead were available for analysis; there was no relationship between condition at banding and whether a bird was found dead (P = 0.19). Waterfowl susceptibility to avian cholera may be unrelated to body condition; therefore, avian cholera mortality may have masked relationships among other mortality causes and condition. J. WILDL. MANAGE. 58(4):787-793

Effects of Ingested Tungsten-Bismuth-Tin Shot on Captive Mallards

Steel shot is required for waterfowl hunting in the United States, but hunter dissatisfaction with steels perceived ballistic performance has reduced compliance with steel shot laws, contributed to the loss of waterfowl hunters nationwide, and renewed interest in an alternative non-toxic shot with ballistic qualities similar to lead shot. We evaluated the acute toxicity of an alternative shot by orally dosing 20 8-week-old game farm mallards (Arras platyrhyrrchos) with 12-17 pellets (x = 1.03 g) composed of tungsten, bismuth, and tin (TBT). Ducks were monitored for 32 days for evidence of intoxication. Eroded shot evident in radiographs taken 11 days post-dosing indicated acute exposure to the constituent metals, but no dosed or undosed birds died during the trial

Ulnar Lipid as an Indicator of Depleted Fat Reserves in Mallards

We wanted to determine if ulnar lipid content of mallards (Anas platyrhynchos) reflected total body lipid, because many scavenged waterfowl carcasses are only represented by wings. Consequently, we euthanized 12 mallards at various stages of starvation to quantify the relationship. Percent ulnar lipid remained constant when total body fat was ≥5%, but ulnar lipid was quickly catabolized when body fat was <5%. With these criteria, we examined ulnar lipid content from 295 mallard carcasses found during the winters of 1987 and 1988 in the San Luis Valley, Colorado. Ulnar lipid did not differ (P=0.83) between years (x=31.0%) for mallards with ulnar lipid levels ≥5%. Females had less (P=0.02) ulnar lipid (x=0.64 g) than males (x=0.74 g) because of their relatively smaller ulnae

An investigation of factors affecting waterfowl hunting participation in Colorado

Abstract A study of 1993 Colorado waterfowl hunters examined factors affecting individuals’ decisions to hunt waterfowl and identified preferences for potential management strategies. This information was used in revising waterfowl regulations in the state. A stratified random sample of 1,400 resident Colorado waterfowl hunters was drawn from 1992–93 Colorado Duck Stamps, 700 from east of the Continental Divide (Central Flyway) and 700 from the west of the Continental Divide (Pacific Flyway). A 13‐page mail questionnaire was sent in June, 1993 to all subjects. Those individuals indicating that they had hunted in 1992–93 were asked to complete the entire questionnaire and were coded as active hunters for the analyses. Those who indicated they had not hunted were asked to return the questionnaire and were subsequently sent an abbreviated questionnaire with some of the same questions as the original survey. Those completing this abbreviated survey were coded as inactive hunters (those who hunted in the past,...