This research was designed to broaden the understanding of how timber-harvest affects aquatic macroinvertebrates in perennial and intermittent headwater streams. This study compared emergent and benthic macroinvertebrate assemblages from 20 headwater streams in the central Oregon Coast Range that varied by harvest condition and flow duration. Through comparison of the...
Island systems and species are susceptible to extinction because of their small population size and an ecological naiveté from an evolutionary past lacking strong competition and predation. For example, only one-fifth of the world’s bird species occur on islands, yet more than 90% of the avian extinctions witnessed during historic...
Previous research in South Fork Hinkle Creek suggested that coastal cutthroat trout exhibit an aggregated spatial pattern across multiple spatial scales. To evaluate the persistence of the observed abundance patterns and identify factors that affect those patterns, half-duplex passive integrated transponders (PIT-tags) were implanted in 320 coastal cutthroat trout (>...
Habitat loss causes a reduction in available resources for wildlife, alters the configuration of remaining habitat, and may isolate wildlife populations. White-breasted nuthatches (Sitta carolinensis) are experiencing long-term population declines in the Willamette Valley of Oregon, where they are historically associated with oak woodlands. As secondary cavity-nesters, white-breasted nuthatches may...
For the first objective of this thesis, we attempt to understand the role of water flow and directionality in determining steelhead (Oncorhynchus mykiss) and spring/summer and fall Chinook (O. tschawytscha) migration patterns within the Columbia River Estuary and plume by integrating recent advances in biotelemetry and environmental observation and forecasting...
Recent studies of headwater streams have demonstrated their importance to overall watershed biodiversity, nutrient cycling, and energy flux. However, little attention has been paid to long-term effects of forest harvest on macroinvertebrate communities in headwater streams. This study investigated headwater stream macroinvertebrate communities in the H.J. Andrews Experimental Forest, Oregon,...
Radiotelemetry was used to study the seasonal movements and habitat use of adult westslope cutthroat trout Oncorhynchus clarki lewisi in Roberts
Creek and Rail Creek, headwater tributaries of the John Day River, Oregon,
from September 2000 to December 2001. The objectives were to (1)
describe adult cutthroat trout life history...
I examined the avian biogeography of the islands of Lago Gatun, Panama, in an effort to better understand the effects of forest fragmentation in this biodiverse region, and specifically to understand the importance of fragment isolation and the mechanism behind its effects on tropical bird distribution. I combined exhaustive surveys...
North American sagebrush (Artemisia spp.) ecosystems are suffering from
reductions in habitat extent and quality. Only about 50% of sagebrush remains
from pre-settlement conditions, and much of the remaining habitat is
fragmented or degraded by invasive species, fire suppression and overgrazing.
Sagebrush-obligate species are experiencing population declines as a result...
I measured responses of free-ranging Rocky Mountain elk (Cervus elaphus) to recreational disturbance at Starkey Experimental Forest and Range, Oregon from April to October, 2003 and 2004. Resting, feeding, and travel activities of 13 cow elk were recorded at 5-minute intervals using Actiwatch™ motion sensors. Elk were subjected to four...
Rotifers and brine shrimp (Artemia) are important prey items for rearing marine fish larvae. Their availability in the water column may be reduced when they are transferred to larval rearing tanks at lower temperature. In this study, Brachionus rotundiformis (SS-type) and Brachionus plicatilis (L-type) were semi-continuously cultured and fed on...
An acceptable microparticulate diet for marine fish larvae may be defined as an artificial diet that contains, retains, and delivers the required nutrients to support survival and growth. Factors affecting ingestion rate of prey items by fish larvae include environmental factors such as light intensity, prey/background contrast, possible chemical cues,...
Pacific rockfishes (genus Sebastes) have attracted wide scientific and public interest from an evolutionary, fishery and conservation standpoints. This dissertation addresses several hypotheses involving spatial and temporal scales of genetic change in two overfished rockfishes, darkblotched (S. crameri) and canary rockfish (S. pinniger), using statistical analyses of genetic variation within...
Seabirds are an integral component of marine ecosystems, however, because humans typically observe only snapshots of their lives at sea, our understanding of seabird foraging ecology is often limited. A more complete understanding of the ecological roles of seabirds and identification of critical foraging habitats requires the ability to follow...
Salmonid run sizes are strongly affected by their early marine stage. Fully understanding the life history of salmonids means understanding how they interact with their marine environment and with other fishes. Changes in the biological and physical environment off the Columbia River region affects the distribution and abundance of predatory...
The goal of this research was to characterize thermal habitat requirements for juvenile redband steelhead trout (Oncorhynchus mykiss gairdneri) in the South Fork John Day River (SFJD), Oregon using physiological indicators of fish condition. Physiological indices of fish condition measured were whole body lipid content and heat shock proteins, specifically...
The goal of this research was to characterize thermal habitat requirements for juvenile redband steelhead trout (Oncorhynchus mykiss gairdneri) in the South Fork John Day River (SFJD), Oregon using physiological indicators of fish condition. Physiological indices of fish condition measured were whole body lipid content and heat shock proteins, specifically...
I studied small-mammal communities and their response to grazing in mixed-conifer forests and oak woodlands in the Cascade-Siskiyou National Monument in southern Oregon. My objectives were to (1) compare small-mammal communities among forest types and grazing intensities, (2) identify riparian affiliated species, and (3) describe microhabitat associations. Over two years,...
Pygmy rabbits (Brachylagus idahoensis) in Oregon and Washington are a sagebrush (Artemisia tridentata spp.) obligate species of concern because of declining populations and extirpation from much of their range. Efforts are underway to establish a captive bred population of the Columbia Basin pygmy rabbit in Washington state for reintroduction into...
Chinook salmon (Oncorhynchus tshawytscha) display the greatest variability of return times to freshwater of all Pacific salmon. Differential return times to freshwater have segregated populations of Chinook into two broad types or runs, fall and spring, named for the time of year in which they migrate to freshwater. Migration time...