Publications

The timing of breeding and molting was studied in six species of Hawaiian honeycreepers with differing food habits on the Island of Hawaii. The availability of nectar was highly seasonal, whereas insect abundance was relatively constant throughout the year. All six species of honeycreeper had extended breeding and molting periods with peak breeding between April and July and peak molting...

We studied populations of the endangered Akepa (Loxops coccineus coccineus) and Hawaii Creeper (Oreomystis mana) at four sites on the island of Hawaii. Mean monthly density (? SL) of Akepa was 5.74 t 0.87, 1.3? 0.41, 0.96 -? 0.13, and 0.76 ? 0.12 Akepa/ha at Kau Forest, Hamakua, Keauhou Ranch, and Kilauea Forest study areas, respectively. Hawaii Creepers were found at densities of 1.68...

No abstract available.

Because count data collected in many bird surveys are only an index to population size, factors that can influence the counts must be identified and incorporated into analyses. Observer quality is often ignored in analyses of population changes from survey data, but observers differ in methods and capabilities and, hence, tend to count different numbers of birds. We assess the...

Using data from the North American Breeding Bird Survey (BBS), continental and regional changes in bird populations were estimated for the 2-year periods of 1991-1992 and 1992-1993. These 2-year changes were placed in the context of population trends since 1966. During 1991-1992, 62% of all species exhibited positive continental trend estimates. For species showing significant population...

We investigated habitat specificity of the amber darter (Percina antesella Williams & Etnier 1977), an imperiled fish from restricted portions of 2 rivers in the southeastern United States. Foraging amber darters occupied a narrow range of riffle habitat, consistently avoiding areas 20 cm deep and with velocity 10 cm. s-1 near the substrate, occupying areas with cobble or gravel...

No abstract available.

This study examines the effects of operational use of pesticides on avian species inhabiting apple orchards in Pennsylvania Mourning dove (Zenaida macroura) and American robin (Turdus migratorius) nests were monitored in three organic and three conventional apple orchards during 1990 and 1991 In 1991 we surveyed the avian communities of these orchards by using line transects...

Reproductive success and contaminant levels in 1986 and 1987 were compared between Barn Swallows nesting at selenium-contaminated Martin Lake, Texas, USA, and swallows nesting at a reference site. Nests were initiated about the same time or earlier at Martin Lake than at the reference site and clutch size was similar between the two locations. Nest success was significantly higher at...

Population densities for small mammal and arthropod populations can be estimated using capture frequencies for a web of traps. A conceptually simple geometric analysis that avoid the need to estimate a point on a density function is proposed. This analysis incorporates data from the outermost rings of traps, explaining large capture frequencies in these rings rather than truncating them...

From 1977–1978 to 1990, concentrations of polychlorinated biphenyls (PCBs) and most organochlorine pesticides declined in eggs of red-breasted mergansers (Mergus serrator) nesting on islands in northwestern Lake Michigan. Total PCBs decreased 60% (from 21 ppm in 1977–1978 to 8.5 ppm in 1990) and p,p′-DDE decreased 66% (from 6.5 to 2.2 ppm). Dieldrin decreased only 16% (from 0.82 to 0.69...

The locations of 22 territorial gray wolves (Canis lupus) killed by conspecifics in northeastern Minnesota were analyzed in a study involving radio-telemetry from 1968 through 1992. Twenty-three percent of the wolves were killed precisely on the borders of their estimated territories; 41%, within 1.0 km (16% of the radius of their mean-estimated territory) inside or outside the estimated...