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Poor water quality and widespread depletion of wild celery (Vallisneria americana) and other submerged aquatic plants important as waterfowl foods has resulted in the continued dependence of canvasbacks (Aythya valisineria) on Baltic clams (Macoma balthica) as their primary winter food. Despite this dependence, no information exists regarding the distribution...

Ten greater sandhill cranes (Grus canadensis tabida), trained to enter and ride in a specially equipped truck, were transported at 80? days of age from their rearing site at Patuxent Wildlife Research Center (Patuxent), Maryland, to a reintroduction site located within the species? former breeding range in northern Arizona....

Numbers of wetlands and amount of surface water (ha) within a 105 km2 area increased substantially between 1958-60 and 1978-80 in southcentral Maine. Conversely, in 1978-80 mean numbers of black duck pairs (11.9/100 ha surface water) and broods (10.8/100 ha surface water) were lower than for 1958-60 (pairs = 23.3;...

If Lawrence's flycatcher of Grenada, Trinidad, and northern South America is placed in the genus Lathrotriccus with the species euleri, it should be L. flaviventris (Lawrence) or L. euleriflaviventris, depending on rank. If it remains in the genus Empidonax, the specific name should be bolivianus Allen....

Ecological and toxicological aspects of zinc in the environment are reviewed with emphasis on natural resources. Subtopics include sources and uses; chemical and biochemical properties; carcinogenicity, mutagenicity, teratogenicity; background concentrations in biological and nonbiological compartments; effects of zinc deficiency; toxic and sublethal effects on terrestrial plants and invertebrates, aquatic organisms,...

We alternately marked 80 juvenile, female mallards (Anas platyrhynchos), half with transmitters and bands and half with only bands in 1990 and 1991. Survival of radio-marked ducks was monitored daily and then summarized weekly for the periods 31 August - 6 December, 1990 (weeks 5-18) and 11 September -...

Two winter bird surveys in Canada have range-wide population monitoring potential: Christmas Bird Counts (CBCs) and Project FeederWatch (PFW). CBC trends are shown to be correlated to Breeding Bird Survey (BBS) trends, whether or not part of the winter range lies outside the CBC coverage area. Some species...

The hydrogeomorphic approach (HGM) of wetland assessment emphasizes functional components of wetlands such as water storage, transformation and cycling of elements, accumulation of sediments, and preservation of habitats. Many of the elements measured in HGM are physical rather than ecological or biological. The HGM approach, therefore, provides information on...

The toxicity of aluminum has been studied extensively in fish, less so in invertebrates, amphibians, and birds, and not at all in reptiles and free-ranging mammals. For aquatic organisms, Al bioavailability and toxicity are intimately related to ambient pH; changes in ambient acidity may affect Al solubility, dissolved Al...

The Midcontinental population of sandhill cranes (Grus canadensis) has a large geographic range, contains nearly 500,000 birds, and is hunted in much of its range. The population includes three subspecies; the numbers of two of these are uncertain, and they should be afforded protection from hunting that would be...

From 19391966, approximately 450 acres of impoundments were created for recreational and wildlife conservation purposes at Patuxent Research Refuge. Impoundments were of three major designs: impounded ravines, excavated basins, and impounded swamps. Over 50 species of wetland plants were transplanted to impoundments of Patuxent to determine best species for...