Publications

Hydrologic data were evaluated from four areas of western Pennsylvania to estimate the minimum depth of well surface casing needed to prevent contamination of most of the fresh gr6unct-water resources by oil and gas wells. The areas are representative of the different types of oil and gas activities and of the ground-water hydrology of most sections of the Appalachian Plateaus...

In 1991, the U.S. Geological Survey (USGS) began a National Water-Quality Assessment (NAWQA) program. The three major objectives of the NAWQA program are to provide a consistent description of current water-quality conditions for a large part of the Nation's water resources, define long-term trends in water quality, and identify, describe, and explain the major factors that affect water...

In 1980, the U.S. Congress mandated the National Acid Precipitation Assessment Program (NAPAP) to study the effects of acidic precipitation (acid rain). In 1982, the U.S. Geological Survey (USGS) was selected to be the lead Federal agency under NAPAP to monitor the composition of precipitation and its effects on the environment. In 1982, the USGS began to monitor precipitation and...

No abstract available.

Because visibility bias can confound attempts to detect changes in abundance, we evaluated factors that affect visibility rate in aerial surveys of wintering waterfowl. We placed waterfowl decoys in 32 2- x 0.25-km strip transects in the Mississippi Alluvial Valley (MAV) during February 1990 and 1991 and observed the decoys under different experimental conditions. Visibility rate was...

We previously presented (Conroy 1985, Conroy et al. 1989) models for analysis of band recovery data stratified into those voluntarily reported and those obtained by solicitation, similar to models described by Pollock et al. (1994). We discuss differences between the 2 modeling approaches and suggest designs and analyses involving overlapping samples of standard and reward bands to...

The green-winged teal (Anas crecca carolinensis) is an important harvest species, yet we know relatively little about its population ecology. We investigated aspects of green-winged teal population ecology of potential importance to waterfowl managers. We used recoveries of green-winged teal banded during winter (1950-89) to establish banding reference areas and estimate survival and...

Long-term effects of disease on wild animal population demography is not well documented. We studied a gray wolf (Canis lupus) population in a 2,060-km2 area of Minnesota for 15 years to determine its response to canine parvovirus (CPV). The CPV had little effect (P > 0.05) on wolf population size while epizootic during 1979-83. However, after CPV became enzootic, percentage of pups...

No abstract available.

The entomopathogenic nematodes Steinernema carpocapsae (Weiser) and S. glaseri (Steiner) are pathogenic to engorged adult, blacklegged ticks, Ixodes scapularis (Say), but not to unfed females, engorged nymphs, or engorged larvae. Nematodes apparently enter the tick through the genital pore, thus precluding infection of immature ticks. The timing of tick mortality, and overall mortality...

1. L. D. Mech et al. presented evidence that moose Alces alces and deer Odocoileus virginianus population parameters re influenced by a cumulative effect of three winters' snow depth. They postulated that snow depth affects adult ungulates cumulatively from winter to winter and results in measurable offspring effects after the third winter. 2. F. Messier challenged those findings and...

No abstract available.