Publications

Biological soil crusts arrest soil erosion and supply nitrogen to arid ecosystems. To understand their recovery from disturbance, we studied performances of Collema spp. lichens relative to four experimental treatments plus microtopography of soil pedicels, oriented north-northwest to south-southeast in crusts. At sites in Needles (NDLS) and Island in the Sky (ISKY) districts of Canyonlands Nation

Rivers and streams, by their very nature long ribbons of aquatic habitat, are inherently difficult to study. Approaching the banks of a flowing-water (lotic) system, one can see only a short fragment of the entire stream, from one bend to another, and can gain little appreciation for important features that lie beyond view. Moreover, materials transported downstream by the flow, and organisms trav

We estimated statewide, regional, and national trends in counts of Bald Eagles (Haliaeetus leucocephalus) along selected routes in the contiguous United States during midwinter, 1986-2000. Each January, several hundred observers collected data as part of a survey initiated by the National Wildlife Federation in 1979. To analyze these data, we used only those routes surveyed consistently in at leas

We determined prevalence and altitudinal distribution of forest birds infected with avian pox at 16 locations on Hawaii, from sea level to tree line in mesic and xeric habitats, during 1977–1980. Isolates from lesions were cultured in the laboratory for positive identification of Poxvirus avium. Infected birds from the wild were brought into the laboratory to assess differences in the course of in

No abstract available.

Among studies that have quantified the care of precocial young, few have investigated forms of parental care other than vigilance. During the pre-fledging period, Tundra Swan (Cygnus columbianus columbianus) parents provided simultaneous biparental care by foraging near each other and their cygnets, and cygnets spent more time foraging during bouts in which both parents were foraging nearby than w

No abstract available.

Using molecular-genetic techniques, we determined the gender of 202 Southwestern Willow Flycatcher (Empidonax traillii extimus) nestlings from 95 nests sampled over a five-year period. Overall nestling sex ratio did not vary significantly from 50:50 among years, by clutch order, or by mating strategy (monogamous vs. polygamous pairings). However, we did observe significant differences among the fo

No abstract available.

In the winters of 1998–1999 and 1999–2000, we tracked 67 radio-marked Dunlin (Calidris alpina) throughout the complex agricultural landscape of the Willamette Valley of Oregon. Individual birds were tracked across 8-week sampling periods and indicated a high degree of regional fidelity throughout the three winter sampling periods. Birds exhibited varied degrees of fidelity to specific wetland site

We compared American White Pelican (Pelecanus erythrorhynchos) soaring flight times and altitudes to model-produced estimates of thermal depth and intensity. These data showed that pelican soaring flight was confined to the thermal layer, and that the vertical extent of the soaring flight envelope increased with increases in thermal depth. Pelicans soaring cross-country between foraging and breedi

Terminal restriction fragment length polymorphism (TRF or T-RFLP) analysis and 16S rDNA sequence analysis from clone libraries were used to examine cyanobacterial diversity in three types of predominant soil crusts in an arid grassland. Total DNA was extracted from cyanobacteria-, lichen-, or moss-dominated crusts that represent different successional stages in crust development, and which contrib