Book Chapters

Under the pressure of increasing human populations and expanding demands for food and fiber, native tropical and temperate habitats are becoming more restricted, and populations of many resident and migratory birds are declining. Mist net surveys of 111 forest and agricultural sites in Mexico, Belize, and Guatemala show that some migratory species use a wide variety of habitats during...

Fringe-toed lizards (Uma spp.) inhabit many of the scattered windblown sand deposits of southeastern California, southwestern Arizona, and northwestern Mexico. These lizards have several specialized adaptations: elongated scales on their hind feet ("fringes") for added traction in loose sand, a shovel-shaped head and a lower jaw adapted to aid diving into and moving short distances...

Colonial waterbirds, that is, seabirds (gulls, terns, cormorants, pelicans) and wading birds (herons, egrets, ibises), have attracted the attention of scientists, conservationists, and the public since the turn of the century when plume hunters nearly drove many species to extinction. The first national wildlife refuge at Pelican Island, Florida, was founded to conserve a large nesting...

White sturgeon (Acipenser transmontanus), the largest freshwater fish in North America, live along the west coast from the Aleutian Islands to central California (Scott and Crossman 1973). Genetically similar reproducing populations inhabit three major river basins: Sacramento-San Joaquin, Columbia, and Fraser. The greatest number of white sturgeon are in the Columbia River Basin.

The common raven (Corvus corax) is a large black passerine bird found throughout the northern hemisphere including western and northern North America. Ravens are scavengers that frequently feed on road-killed animals, large dead mammals, and human refuse. They kill and eat prey including rodents, lambs (Larsen and Dietrich 1970), birds, frogs, scorpions, beetles, lizards, and snakes...

Roadside point counts are generally used for large surveys to increase the number of samples. We examined differences in species detected from roadside versus off-road (200-m and 400-ha) point counts in the Shenandoah National Park. We also compared the list of species detected in the first 3 minutes to those detected in 10 minutes for potential species biases. Results from 81 paired...

U.S. Department of Agriculture programs have mediated supply and demand of commodities and maintained the agricultural industry, but several programs have also offered various kinds of conservation benefits. The 1985 Food Security Act (Farm Bill) featured the Conservation Reserve Program (CRP), which paid farmers to plant perennial cover on highly erodible lands and to leave this land...

We delineate bird populations using cluster analysis to group ringing sites based on pairwise comparisons of recoveries. Clustering provides a quantitative (but non-unique) grouping that can be used to examine the relationships of bird distributions at both local and regional geographic scales. Clustering is based on similarity matrices composed of pairwise comparisons of recovery...

The desert tortoise (Gopherus agassizii) is a widespread species of the southwestern United States and Mexico. Within the United States, desert tortoises live in the Mojave, Colorado, and Sonoran deserts of southeastern California, southern Nevada, southwestern Utah, and western Arizona (Fig. 1). A substantial portion of the habitat is on lands administered by the U.S. Department of the...

No abstract available

In the spring of 1983 the last known Tarahumara frog in the United States was found dead. Overall, the species seems to be doing well in Mexico, although the decline of more northern populations are of concern. The Tarahumara frog (Rana tarahumarae) inhabits seasonal and permanent bedrock and bouldery streams in the foothills and main mountain mass of the Sierra Madre Occidental of...

Since the early 1970's, the numbers of some waterfowl species such as mallard (Anas platyrhynchos), blue-winged teal (A. discors), and northern pintail (A. acuta) have reached or nearly reached the lowest ever recorded. Low nest success (the proportion of nests in which one or more eggs hatch) in key breeding areas, including the U.S. Prairie Pothole region, is partly responsible for...