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At least 901 records · Page 50Linked to original sources
USGS2001

Declining ring-necked pheasants in the Klamath Basin, California: II. Survival, productivity, and cover

Cover condition and its influence on nesting success, survival, and body condition of ring-necked pheasants (Phasianus colchicus) were evaluated at Tule Lake National Wildlife Refuge (TLNWR) and Lower Klamath National Wildlife Refuge (LKNWR). Inadequate nesting cover was responsible for extremely low nest success early in the nesting season at TLNWR. Later in the season at TLNWR, spring-planted crops provided cover to conceal nesting and renesting hens; however, only 0.07 young were produced (to 1 August) per hen during the study. The extremely low reproductive rates were well below those required to maintain a stable population. At TLNWR, most adult mortality during spring and early summer (before crops provided adequate cover) apparently resulted from predation by golden eagles (Aquila chrysaetos). This mortality occurred weeks before insecticide applications. Hard winters (cold temperatures and heavy snowfall) periodically reduce the pheasant population in the Klamath Basin and again greatly reduced numbers during the last year of this study. Unfortunately, pheasant populations declined under the conditions found during this study and were unable to recover from the hard winter of 1992 to 1993. Mean body mass and tarsal length of adult hen pheasants at TLNWR, which is intensively farmed, were less than those for hens at LKNWR, which is not intensively farmed. Results of our study suggest that TLNWR hens may have been nutritionally stressed, and that the amount and distribution of vegetative cover needs to be improved at TLNWR. Habitat management of edge cover along agricultural crops should feature perennial grasses and legumes with small tracts of land interspersed throughout the agricultural fields to provide alternative cover for wildlife in general including pheasants.

Northwestern Naturalist↗
USGS2001

Effects of exotic species on Yellowstone's grizzly bears

Humans have affected grizzly bears ( Ursus arctos horribilis ) by direct mortality, competition for space and resources, and introduction of exotic species. Exotic organisms that have affected grizzly bears in the Greater Yellowstone Area include common dandelion ( Taraxacum officinale ), nonnative clovers ( Trifolium spp.), domesticated livestock, bovine brucellosis ( Brucella abortus ), lake trout ( Salvelinus namaycush ), and white pine blister rust ( Cronartium ribicola ). Some bears consume substantial amounts of dandelion and clover. However, these exotic foods provide little digested energy compared to higher-quality bear foods. Domestic livestock are of greater energetic value, but use of this food by bears often leads to conflicts with humans and subsequent increases in bear mortality. Lake trout, blister rust, and brucellosis diminish grizzly bears foods. Lake trout prey on native cutthroat trout ( Oncorhynchus clarkii ) in Yellowstone Lake; white pine blister rust has the potential to destroy native whitebark pine ( Pinus albicaulis ) stands; and management response to bovine brucellosis, a disease found in the Yellowstone bison (Bison bison) and elk ( Cervus elaphus ), could reduce populations of these 2 species. Exotic species will likely cause more harm than good for Yellowstone grizzly bears. Managers have few options to mitigate or contain the impacts of exotics on Yellowstone's grizzly bears. Moreover, their potential negative impacts have only begun to unfold. Exotic species may lead to the loss of substantial highquality grizzly bear foods, including much of the bison, trout, and pine seeds that Yellowstone grizzly bears currently depend upon.

Wyoming↗
USGS2004

Cannibalism and predation by western toad (Bufo boreas boreas) larvae in Oregon, USA

Larval amphibians have been widely used as model organisms in studies of community ecology of freshwater systems (Morin 1983, Alford 1999). Much of this work has assumed that trophic effects of larval anurans are focused on periphyton and planktonic algae (Dickman 1968, Seale 1980, Duellman and Trueb 1986), a view that has recently been questioned. Recent experiments suggest that anuran larvae can occupy broader trophic roles than previously believed and may function as important predators in some pond communities (Petranka et al. 1994, Petranka and Kennedy 1999)

Oregon↗
USGS2005

Monitoring temporal change in riparian vegetation of Great Basin National Park

Disturbance in riparian areas of semiarid ecosystems involves complex interactions of pulsed hydrologic flows, herbivory, fire, climatic effects, and anthropogenic influences. We resampled riparian vegetation within ten 10-m × 100-m plots that were initially sampled in 1992 in 4 watersheds of the Snake Range, east central Nevada. Our finding of significantly lower coverage of grasses, forbs, and shrubs within plots in 2001 compared with 1992 was not consistent with the management decision to remove livestock grazing from the watersheds in 1999. Change over time in cover of life-forms or bare ground was not predicted by scat counts within plots in 2001. Cover results were also not well explained by variability between the 2 sampling periods in either density of native herbivores or annual precipitation. In contrast, Engelmann spruce ( Picea engelmannii ) exhibited reduced abundance at all but the highest-elevation plot in which it occurred in 1992, and the magnitude of change in abundance was strongly predicted by plot elevation. Abundance of white fir ( Abies concolor ) individuals increased while aspen ( Populus tremuloides ) individuals decreased at 4 of 5 sites where they were sympatric, and changes in abundance in the 2 species were negatively correlated across those sites. Utility of monitoring data to detect change over time and contribute to adaptive management will vary with sample size, observer bias, use of repeatable or published methods, and precision of measurements, among other factors.

Nevada↗
USGS2006

Populations and habitat relationships of Piute ground squirrels in southwest Idaho

Piute ground squirrels (Spermophilus mollis idahoensis) are normally above ground from late January until late June or early July in the Snake River Birds of Prey National Conservation Area in southwestern Idaho. In 2002 they were rarely seen above ground after early May. Because of the ecological importance of ground squirrels for nesting raptors and other species, we sought to determine the reasons for their early disappearance. We sampled 12 sites from January 2003 through March 2003 to determine if a population crash had occurred in 2002. Tests indicated that Piute ground squirrels had not been exposed to plague within the past year. The presence of yearlings in the population indicated that squirrels reproduced in 2002 and that at least some yearlings survived the winter. Both yearling and adult squirrels appeared to be reproducing at or above normal rates in 2003. The most plausible explanation for the early disappearance of Piute ground squirrels in 2002 is that squirrels entered seasonal torpor early in response to a late spring drought. In addition, the breeding chronology of squirrels may have shifted during the past 2 decades in response to climate change and/or habitat alteration. Shrub habitats provide a more favorable and stable environment for squirrels than grass habitats. Squirrel abundance was higher on live-trapping grids with sagebrush than on grids dominated by grass, and squirrel masses were higher at sites dominated by shrubs and Sandberg bluegrass (Poa secunda). Densities in big sagebrush (Artemisia tridentata) were within the ranges reported for earlier years, but densities in grass were lower than previously reported. Low densities at grassland sites in 2003 support other findings that drought affects squirrels in altered grass communities more than those in native shrub habitats. Long-term shifts in ground squirrel breeding chronology may have implications for raptors that depend on them for food.

Western North American Naturalist↗
USGS1994

Predation by dipteran larvae on fairy shrimp (Crustacea: Anostraca) in Utah rock pools

A series of experiments examined how ecological factors affect notonectid foraging success on fairy shrimp. Variation in pond depth over natural ranges had no direct effect on notonectid ability to capture fairy shrimp. Decreases in water clarity over natural ranges led to decreased notonectid ability to capture fairy shrimp. This corresponds with the observation that six weeks after the fairy shrimp hatched they were more likely to be present in cloudy ponds than in ponds containing clearer water. If correct, this is a situation where physical factors have a major effect on how a biological interaction influences the local distribution of species. It appears water depth indirectly affects notonectid foraging rates, as shallow ponds are apparently made cloudy by wind-driven waves disturbing the bottom mud. These results suggest the notonectid-fairy shrimp interaction will not be a constant for any given pond, but will depend on abiotic factors like amount of rainfall and frequency of windy conditions.

Southwestern Naturalist↗
USGS1977

In search of eagles

Review of: Golden eagle country. Richard R. Olendorff. Knopf; 1st edition (1975). 202 p. ISBN: 0394482921.

Prairie Naturalist↗