Publications

The 40Ar/39Ar ages of a sanidine clast from a melt-matrix breccia of the Manson, Iowa, impact structure (MIS) indicate that the MIS formed 73.8 ± 0.3 million years ago (Ma) and is not coincident with the Cretaceous-Tertiary boundary (64.43 ± 0.05 Ma). The MIS sanidine is 9 million years older than 40Ar/39Ar age spectra of MIS shock-metamorphosed microcline and melt-matrix breccia...

Low annual survival of hatching-year (HY) females is a critical management concern for canvasbacks (Aythya valisineria), and may contribute substantially to reduced reproductive potential and the male-biased sex ratio of the species. To evaluate the contribution of mortality on a traditional wintering area to low annual survival, we estimated survival rates of HY female canvasbacks...

Phenacosaurus neblininus, new species, was discovered during the 1984-1985 expedition to Cerro de la Neblina on the Venezuelan-Brazilian border. It was found at several highland camps (> 1600 m) but seems unaccountably rare, with only six specimens collected. The closest relative of this lizard may be another new species (Williams et al., MS) known from a single specimen from Chimanta...

Transmission risk of Lyme disease at a site can be estimated using the probability of exposure (P1 = probability of being bitten by at least one infected tick); P1 =1 - (1 - kt)n, where n = number of tick bites per person and kt = spirochete prevalence in questing ticks. This probability is more directly related to the likelihood of acquiring Lyme disease than the standard measure of...

Northern pintails (Anas acuta) exist as a single circumpolar breeding population but display weak fidelity to given breeding sites. If fidelity to wintering areas is strong, management on wintering grounds may allow local winter populations to increase. Thus, I delineated reference areas for wintering areas based on recovery data for pintails banded during the winter (Dec-Feb) in the...

From 1950 through 1988, the continental breeding population of northern pintails (Anas acuta) varied from 2.0 million to 9.9 million. Because pintails have high fidelity to certain wintering grounds along coasts and large bodies of water, management on these wintering areas may increase population size if changes in winter survival rate are related to changes in population size. I used...

No abstract available.

No abstract available.

A study of wood ducks (Aix sponsa) was conducted along the Coeur d'Alene River system in northern Idaho in 1986 and 1987. Most of this area has been subjected to severe contamination from lead and other metals from mining and smelting since the 1880s. In 1986, a preliminary study of wood duck nesting was conducted in the contaminated area; incubating hens captured in nest boxes were bled...

The latest and most innovative technology has been applied towards the development of a full-ocean depth multi-sensor sonar system using linear swept-FM (Chirp) technology. The seafloor imaging system (SIS- 7000) described herein uses Chirp sidescan sonar to provide high resolution imagery at long range, and Chirp subbottom sonar to provide high resolution profiles in both the near...

For 5 years we used seawater tolerance tests (seawater challenges) to identify smolts, and tunnel fish counters to record the time of migration, of Atlantic salmon Salmo salar that volitionally left holding ponds on the Merrimack River near Litchfield, New Hampshire. We compared timing of Atlantic salmon movements with environmental conditions and blood composition of migrating and...

The Green Lake, Wisconsin, strain of lake trout Salvelinus namaycush was discontinued as a hatchery brood stock in 1976 after Lake Michigan was stocked with the 1975 year‐class. In 1982, a decision was made to restore the Green Lake strain as a production brood stock. Five groups were produced by spawning marked fish that were survivors from the 1976 stocking of southern Lake Michigan. A...