Publications

For four consecutive years, following the fires in November 1993, temporal variations in species richness, cover and biomass of component plant groups in early post-fire chaparral succession were monitored on different aspects at the Stunt Ranch Santa Monica Mountains Reserve, southern California. Plant groups were categorized based on growth form, life form, ability to fix nitrogen...

An objective method for measuring bovine sperm nuclear shape was developed. Digital images of bovine sperm stained with propidium iodide were collected and Fourier functions used to describe the perimeters of individual sperm nuclei. Harmonic amplitudes from Fourier functions were first shown to be independent of sperm orientation during digitization. Sperm from 12 different bulls were...

Previous reports described an increase in population density following the removal of 23 adult male black bears (Ursus americanus) from a 218-km2 study area near Cold Lake, Alberta (the CLSA). This finding plays a central role in continuing debates over population regulation in bears, but has recently been criticized because density estimates were based on assumptions that were not met...

Knowledge of survival of female ducks is important for understanding population dynamics and managing hunted species. We estimated survival of female wood ducks (Aix sponsa) during brood rearing in different wetland environments in Mississippi (1996-1999) and Alabama (1998-1999). Survival was 0.90 ± 0.05 (Ŝ ± SE) in Mississippi and 0.92 ± 0.07 in Alabama. A composite estimate of female...

The Prairie Pothole Region of the northern Great Plains is an important region for waterfowl production because of the abundance of shallow wetlands. The ecological significance of the region and impacts from intensive agriculture prompted the U.S. Environmental Protection Agency to select it as one of the first areas for developing and evaluating ecological indicators of wetland...

The ability of alien plant species to invade a region depends not only on attributes of the plant, but on characteristics of the habitat being invaded. Here, we examine characteristics that may influence the success of alien plant invasion in mixed-grass prairie at Theodore Roosevelt National Park, in western North Dakota, USA. The park consists of two geographically separate units with...

The expansion and contraction of marginal cropland in the Great Plains often involves small forested strips of land that provide important ecological benefits. The effect of human disturbance on these forests is not well known. Because of their unique structure such forests are not well-represented by forest gap models. In this paper, the development, testing and application of a new...

BEHAVE, a fire behavior prediction system, can be a useful tool for managing areas with prescribed fire. However, the proper choice of fuel models can be critical in developing management scenarios. BEHAVE predictions were evaluated using four standardized fuel models that partially described oak savanna fuel conditions: Fuel Model 1 (Short Grass), 2 (Timber and Grass), 3 (Tall Grass)...

Dabbling ducks Genus Anas occasionally nest during mid- and late summer in the Prairie Pothole Region (PPR) of midcontinent North America but little information is available on their Autumn-reared broods or those of other duck genera. Densities, species composition, and wetland habitat use by Autumn reared duck broods (age classes I and II) were determined on randomly distributed...

Males of polygynous bird species typically provide less parental care to their offspring than males of monogamous species (Ketterson and Nolan 1994). Generally, in polygynous species, a male forfeits some potential reproductive success if he shifts his reproductive effort from mating with multiple females to parental care (Trivers 1972, Gubemick et al. 1993, Schleicher et al. 1993). In...

Seven adult female White-tailed Deer (Odocoileus virginianus) in northeastern Minnesota lived within 1.8 km of Wolf pack (Canis lupus) homesites without vacating their home ranges. Six of these deer and at least three of their fawns survived through the Wolf homesite period.

Researchers have suggested that Brown-headed Cowbirds (Molothrus ater) destroy nest contents of potential hosts to induce renesting and thus enhance future opportunities for parasitism. Although cowbird destruction of passerine nests has been witnessed and surmised, few data are available on frequency of those events. We used miniature video-cameras at nests of grassland passerines and...