Population irruption of the least weasel (Mustela nivalis) in east central North Dakota
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Franklin's Ground Squirrels (Spermophilus franklinii) preyed on eggs in 29 of 30 tests in which they were exposed to two Mallard (Anas platyrhynchos) or two Blue-winged Teal (A. discors) eggs and their discovery of eggs was confirmed. No Richardson's (S. richardsonii) or Thirteen-lined (S. tridecemlineatus) ground squirrels preyed on eggs in 104 and 54 similar tests, respectively. Franklin's Ground Squirrels exposed to clutches of six duck eggs placed in simulated nests preyed on all such clutches. Predation on simulated nests began soon after eggs were discovered, but predation of all eggs often took more than one day to complete.
Detailed study of radio-equipped individuals of the Striped Skunk (Mephitis mephitis) in a North Dakota population provided insight into possible mechanisms for spread of rabies during spring and summer. Annual recurrence rates of 138 skunks marked on a study area averaged 11% for adult males, 43% for adult females and 9% for kits. Population changes were from mortality (including rabies) and dispersal. Five instances of adult dispersal (four by males) were recorded; maximum straight-line distance was 119 km. Some males initiated dispersal in spring. Communal denning by adults occurred rarely after whelping began but resulted in intraspecific conflict. Evidence of intraspecific and interspecific strife leading to kit mortality and some adult mortality was found at dens of 9 of 40 litters studied.
Stomach contents of 70 red foxes (Vulpes vulpes) shot in east-central North Dakota during January 1982 and January 1983 were examined. Commercial sunflower seeds were the most frequently found food item, occurring each year in three-fourths of the stomachs and composing about half of the contents. The remainder of the diet was primarily mammals, but included birds, insects, amphibians, and refuse.
Abstract has not been submitted
Habitat use and survival by nine mallard (Anas platyrhynchos) broods from nests on the James River floodplain and adjacent drift plain were monitored during summer 1987. Radio-marked broods were relocated an average of 22% of the time in the river channel, 22% in oxbow ponds, 43% in a large sewage lagoon complex, and 13% in basin wetlands. Four of the six broods hatched on the floodplain stayed primarily in riverine wetlands throughout the brood-rearing period. Seven of nine broods fledged at least one young; a total of 27 ducklings survived to fledging of the 82 that hatched. The seven hens that fledged young used an average of two wetlands each from hatching to fledging. Mink and raptor predation and adverse weather conditions were the principal identified causes of mortality. Potential effects on waterfowl production of planned downstream irrigation, a part of the Reformulated Garrison Diversion Unit, are discussed and recommendations are made to reduce adverse impacts to wildlife.
Canvasback (Aythya valisineria) broods (n = 69) accompanying marked females were observed during five summers in southwestern Manitoba. We evaluated movements of broods of different age classes ( 14 days old, 15-28 days old, and >28 days old) among ponds of different size and wetland class. Of 202 brood sightings, 7% occurred on seasonal ponds, 81% on semipermanent ponds, and 12% on permanent ponds. Pond size ( 0.2 ha vs. >0.2 ha) was a significant factor in brood use whereas wetland class was not. Canvasback broods used larger ponds as brood age class increased. Broods moved an average of 195 m between sightings. Eighty-three percent of broods observed within seven days of hatching (n = 46) had moved from the nesting pond. No significant differences in frequency or distance of movements were detected among years or among brood age classes. Extensive movements among ponds of various sizes and classes emphasize the importance of wetland complexes for providing diverse habitats needed for nesting and brood-rearing canvasbacks.
Populations and distribution of breeding birds occupying wooded draws were studied in a five-county region of western North Dakota during June 1982. Wooded draw vegetation was dominated by green ash, which occurred in 96% of the draws sampled. Chokecherry and juneberry were the most frequent shrub species. I recorded 49 bird species in the 30 draws censused. Rufous-sided towhee, brown-headed cowbird, house wren, and American goldfinch were the most numerous bird species present. Significant correlations were found between (1) the number of live trees and bird species evenness, (2) density of dead trees and bird species diversity and richness, (3) density of shrubs with bird species evenness, and (4) foliage volume in the high ground layer and bird species evenness.
Abstract has not been submitted