ScholarWorks@UA: Recent submissions
Now showing items 21-40 of 12068
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Habitat selection and reproductive ecology among Townsend's warblers (Dendroica townsendi) in southcentral AlaskaI investigated habitat selection and reproductive ecology among Townsend's Warblers (Dendroica townsendi) in mature mixed forests near Anchorage, Alaska. I examined selection of territories, nest sites, and foraging sites to identify habitat features associated with each resource. Male pairing and nest survival were monitored to identify factors influencing reproductive success. Females were highly selective for large white spruce (Picea glauca) as nest sites. Foraging behavior varied temporally and was specialized toward medium white spruce early in the breeding season but subsequently generalized across substrates. Territories were heterogeneous in habitat and were characterized by habitat features selected for nesting and foraging, suggesting specific demands for resources influenced choice of territories. Pairing success (98%) and nest success (51%) were generally higher than that of migratory songbirds breeding in forest fragments. Nest predation and blow fly (Protocalliphora) parasitism, factors constraining reproductive output, varied with microhabitat, suggesting that habitat selection may mitigate their effects.
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Evaluation of sampling gears for fish population assessment in Alaskan streams and riversDuring summers, 1982 and 1983, a variety of habitats were sampled on the Tanana and Kenai River drainages to evaluate sampling gears used for fish population assessment in Alaskan streams and rivers. Experiments were conducted to investigate sampling efficiency, length and species selectivity, and injuries to fish by three active (backpack electroshocker, electrofishing boat, seine), and two passive (minnow trap, fyke net) gear types. Gears were compared using a common set of attributes: accuracy, portability, scope or species detection, labor required, fishing power, fish savings (low mortality), and initial cost. Electrofishing systems were best for species detection and fishing power, while passive gears had higher catch per hour of labor. Large fyke nets and seines were effective under limited environmental conditions. A linear model was developed to assist in selecting an optimum fishing gear, or array of gears, for any level of fisheries population assessment, considering all applicable sampling constraints.
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Climate and caribou: effects of summer weather on the Chisana caribou herdIn 1989, the Chisana caribou (Rangifer tarandus) herd in the northern Wrangell Mountains, Alaska declined substantially in population size and productivity. Summers were significantly warmer and slightly drier during years the herd was declining (1989-1995) compared with years when the herd was stable or increasing (1981-1988). We increased air temperature and decreased precipitation with a plastic tent, decreased light intensity with a shade cloth, and increased precipitation by adding water to determine climatic effects on nutrient content and biomass of caribou forage during summer in 1994 and 1995 in the subarctic tundra. We determined that short-term variations in climate affected nutrient quality, particularly nitrogen content, in above-ground biomass of caribou forage. The warmer, drier summers (1989-1995) may have affected the Chisana population adversely by increasing insect harassment and decreasing nitrogen content in their forage.
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Alaska Earthquake Center Quarterly Technical Report July-September 2023This series of technical quarterly reports from the Alaska Earthquake Center (AEC) includes detailed summaries and updates on Alaska seismicity, the AEC seismic network and stations, field work, our social media presence, and lists publications and presentations by AEC staff. Multiple AEC staff members contribute to this report. It is issued in the following month after the completion of each quarter Q1: January-March, Q2: April-June, Q3: July-September, and Q4: October-December. The first report was published for January-March, 2021.