Now showing items 101-120 of 979

• #### Population status and patterns of distribution and productivity of kittiwakes on St. George Island, Alaska

I studied populations, distributions, and reproductive performance of red-legged and black-legged kittiwakes on St. George Island in the summers of 1993-1995, where populations of both species have experienced generally poor reproductive performance and population declines of ca. 40% over the past 20 years. In 1995, I conducted a whole-island census of kittiwakes on St. George Island and found estimated breeding populations of 193,930 red-legged kittiwakes (81% of their global population), and 62,568 black-legged kittiwakes. In addition, I analyzed census trends on 51 land-based census plots on St. George Island and found that numbers of both species have stabilized in recent years. I experimentally evaluated the hypothesis that nesting red-legged kittiwakes on St. George Island are competitively displaced by larger-bodied black-legged kittiwakes to narrower rock ledges and higher elevations. I determined nest-site preferences of both species by attaching narrow and wide artificial nesting ledges within high-and low-elevation areas of St. George Island and found no evidence of competitive displacement: red-legged kittiwakes preferred narrow ledges, black-legged kittiwakes preferred wide ledges, and both species preferred ledges in areas where conspecifics nested at high density. Multiple regression analyses suggested that kittiwakes breed earlier and more successfully in summers preceded by cold winters and that inter-annual variability in kittiwake breeding success was unrelated to weather conditions during the breeding season itself. These results suggest that winter weather has indirect effects on breeding kittiwakes by influencing prey abundance several months later. Furthermore, strong winds impaired growth rates of kittiwake chicks in exposed nest sites and the growth of black-legged kittiwake chicks relative to red-legged kittiwake chicks. I identified two prominent patterns of within-colony spatial variability in kittiwake productivity and suggest that patchy "bird quality" or localized "information neighborhoods" may be responsible because traditional explanations do not apply. The "information neighborhood" is a new hypothesis which proposes that individuals are influenced by the breeding status of neighbors because their status represents an additional source of information about current breeding conditions that can be used to better tailor parental investment.
• #### Oceanic emissions of sulfur: Application of new techniques

Sulfur gases and aerosols are important in the atmosphere because they play major roles in acid rain, arctic haze, air pollution, and climate. Globally, man-made and natural sulfur emissions are comparable in magnitude. The major natural source is dimethyl sulfide (DMS) from the oceans, where it originates from the degradation of dimethysulfonioproprionate (DMSP), a compound produced by marine phytoplankton. Global budgets of natural sulfur emissions are uncertain because of (1) the uncertainty in the traditional method used to estimate DMS sea-to-air flux, and (2) the spatial and temporal variability of DMS sea-to-air flux. We have worked to lessen the uncertainty on both fronts. The commonly used method for estimating DMS sea-to-air flux is certain to a factor of two, at best. We used a novel instrumental technique to measure, for the first time, sulfur gas concentration fluctuations in the marine boundary layer. The measured concentration fluctuations were then used with two established micrometeorological techniques to estimate sea-to-air flux of sulfur. Both methods appear to be more accurate than the commonly used one. The analytical instrument we used in our studies shows potential as a direct flux measurement device. High primary productivity in high-latitude oceans suggests a potentially large DMS source from northern oceans. To begin to investigate this hypothesis, we have measured DMS in the air over northern oceans around Alaska. For integrating and extrapolating field measurements over larger areas and longer time periods, we have developed a model of DMS ocean mixing, biological production, and sea-to-air flux of DMS. The model's main utility is in gaining intuition on which parameters are most important to DMS sea-to-air flux. This information, along with a direct flux measurement capability, are crucial steps toward the long-term goal of remotely sensing DMS flux. A remote sensing approach will mitigate the problems of spatial and temporal variability. The new developments in methodology, field sampling, and modeling put forth in this thesis are tools we have used to better understand and quantify sulfur gas emissions from northern oceans, which appear to be a significant source of sulfur to the global atmosphere.
• #### Factors affecting the growth of a Black Guillemot colony in northern Alaska

Annual variation in breeding populations at seabird colonies has been well documented, but there have been few long-term attempts to examine the environmental and demographic forces responsible. I studied breeding chronology and demography Black Guillemot in northern Alaska from 1975-1997 to identify the factors responsible for colony establishment and growth. The Black Guillemot is a cavity-nesting seabird whose populations are frequently limited by nest-site availability. Snowmelt in spring and snow accumulation in autumn had major effects on annual nesting initiation and success, respectively. Annual arrival at the colony and median date of egg laying was well correlated with the date of snow disappearance, with annual clutch initiation advancing 4.5 days per decade in response to regional climate amelioration. Successful breeding requires a snowfree cavity for >80 days. Decreased breeding success and post-fledging survival occurred in a year with a snow-free period <80 days. Historic weather records indicate annual snowfree periods >80 days were uncommon until the 1960's, when the species was first recorded breeding in northern Alaska. When additional nest sites were provided, growth of the colony was rapid, increasing from 18 pairs in 1975 to 225 pairs in 1989. Breeding numbers then decreased to 150 in 1996 as factors other than nest-site availability controlled population size. Annual population growth averaged 37% from 1976-1982 when nest site occupancy was low, 3% from 1983-1989 when all or most nesting cavities were occupied, and -6% from 1990-1996 as breeding productivity decreased and mortality of adults increased. Without immigration and with the average annual vital rates the colony would have had an annual rate of growth of 4% during this study. Contrary to published models of seabird colony growth, I found immigration important (>60% of annual recruitment) in all phases of growth. Philopatry showed previously unreported large variation among cohorts related to variation in nest-site vacancies at the natal colony and estimated recruitment opportunities at regional colonies. Philopatry was highest (>80%) for cohorts maturing when most regional recruitment opportunities were at the study colony but low (15%) when nest-site availability was likely similar at the natal colony and other colonies in the region.
• #### Blood organochlorines, immune function and health of free-ranging northern fur seal pups (Callorhinus ursinus)

This study examined organochlorine (OC) contaminant levels in blood and milk along with immune function and health of northern fur seals ( Callorhinus ursinus) from St. George Island, Alaska. This portion of the Pribilof Islands breeding stock has undergone a long-term decline between 4 and 6% per year for unknown reasons. To examine the possible role of neonatal OC exposure on health, two cohorts of pups (69 total) and 33 matched periparturient dams were captured for blood and milk sample collection. From the second cohort of 49 neonates, 43 were re-sampled 29 to 51 days later. OCs were extracted from whole blood and milk to identify 15 polychlorinated biphenyl (PCB) congeners and 4 metabolites of dichloro-diphenyl-trichloroethane by high performance liquid chromatography. Peripheral blood lymphocytes were isolated and cryopreserved for in vitro lymphoproliferative immunoassays. These cellular function assays, along with complete blood cell counts, growth rates and survival through the early developmental period, were used as indicators of health status. Humoral immune function was assessed by in vivo antibody responses to tetanus vaccination. Mean blood levels of PCBs were higher in neonate samples than in pups one to two months old. Seven of the eight congeners detected in blood were higher (lipid weight) in neonate blood than in dam blood or milk. First-born neonates were exposed to higher levels of OCs from ingested milk and had higher blood levels of OCs than neonates of older, multiparous dams. Higher OC exposure in neonates was correlated to higher blood OC levels and poorer lymphoproliferative responses as well as lowered serum. retinol and thyroxine. Higher proportions of pups born to old dams developed tetanus antibodies compared to the pups of young dams. Higher OC exposure and poor immune responses in first-born pups may indicate a higher risk of secondary morbidity and mortality than for pups born to multiparous dams but an affect on growth rate or survival to midway through the nursing period was not detected. Evidence of substantial OC contaminant exposure at a critical period of development for the immune system must be considered as a potential contributing factor to reduced post-weaning survival.
• #### Molecular systematics and biogeography of long-tailed shrews (Insectivora: Sorex) and northern flying squirrels (Rodentia: Glaucomys)

Insight into phylogenetic and biogeographic relationships among several mammalian taxa in western North America was provided with DNA sequences of two mitochondrial genes (cytochrome b and ND4). Members of two species complexes of long-tailed shrews (genus Sorex ) and northern flying squirrels (genus Glaucomys) were examined, and a common theme of responses to past climate change and glacial cycles was evident. Diversification events indicated by the DNA sequences provide new perspectives regarding the deep and shallow history of these taxa. Analysis of seven species of the Sorex cinereus complex (and related species) revealed two major clades within the complex, Northern and Southern. These generally corroborate proposed morphological relationships and correspond to broadly defined habitat affiliations (xeric and mesic), respectively. Within the Northern clade, amphiberingian species represented a monophyletic group suggesting Beringia was a center of endemism. Next, five species of the S. vagrans complex and related species were assessed. Significant molecular variation was revealed that does not correspond to morphological differences within the complex. Two major clades within S. monticolus were observed, a widespread Continental clade (Arizona to Alaska, including S. neomexicanus) and a restricted Coastal clade (Oregon to southeast Alaska, including S. bairdi and S. pacificus). A regional examination of genetic variation in the northern flying squirrel in southeast Alaska was also performed. Results suggested that southern islands in the Alexander Archipelago were the result of recent colonization (founder event). Finally, a comparative phylogeographic analysis of a reduced data set (S. monticolus), a molecular data set for the American Pine Marten, Martes americana, and other published molecular studies were used to reexamine the role of glacial refugia in the biogeography of the north Pacific coast. Previous ideas regarding purported refugia may be overstated and may be the result of limited geographic sampling. This thesis provides new perspectives on processes (e.g., post-glacial colonization) driving mammalian phylogenetic and biogeographic structuring in western North America.
• #### Foraging ecology and conservation biology of African elephants: Ecological and evolutionary perspectives on elephant-woody plant interactions in African landscapes

The available scientific evidence indicates that African forest elephants and bush elephants are ecologically and evolutionarily distinct taxa. The current practice of regarding these two taxa as ecotypes of a single species, Loxodonta africana (i.e., L. a. africana Blumenbach 1797, L. a. cyclotis Matschie 1900) appears unwarranted, and obscures issues of major significance to the conservation biology of African elephants. Under a proposed taxonomic revision, the African bush elephant retains the designation Loxodonta africana Blumenbach 1797 while the African forest elephant is recognized as Loxodonta cyclotis Noack 1906. The browsing of woody plants by African bush elephants is a major factor in the structural dynamics of semi-arid woodland and scrubland habitats in Hwange National Park (HNP) and the Sengwa Wildlife Research Area (SWRA), Zimbabwe. Drought, frost and fire also influence the structure and species composition of woody vegetation within HNP. Interactions among these three abiotic factors and elephant browsing may have significant impacts on the dynamics of semi-arid woodland and scrubland habitats of HNP. Mortality attributable to elephant damage was identified as a principal cause of death among large trees (>5.0 in height), and a relatively minor but not insignificant cause of death for shrubs and trees in the 1.0--5.0 in height class. The responses of Colophospermum mopane in SWRA to fertilization treatments corresponded to those predicted by the carbon/nutrient hypothesis of plant anti-herbivore defense. Comparisons of these results with those of previous studies suggest possible changes in the ecology and population biology of elephants in HNP during the past decade. Observed differences in the age-specific mortality of elephant in HNP during die-offs in 1993--1995 and 1980--1984 provide independent evidence of changes in the ecology of elephants in HNP during the period 1983--1993. The population of L. a. africana inhabiting the Matabeleland-Ngamiland-Okavango region of southern central Africa (which includes the HNP population), is the largest extant elephant population on Earth. The magnitude of this population (110,000--120,000), and the high proportion of its range currently under protection as wildlife reserves, indicate that this population may rank as the most viable and potentially sustainable elephant population on Earth.
• #### New instrumentation for the detection of sulfur dioxide in the remote atmosphere

Sulfur gases are an important chemical component of the atmosphere. Gaseous sulfur compounds effect the acidity of rainwater and are important precursors to aerosol particles which affect public health, climate and visibility of scenic vistas such as the Grand Canyon. Sulfate aerosols are also known to participate in ozone catalysis in the stratosphere. A vast majority of the gaseous sulfur cycling through the atmosphere will exist as sulfur dioxide (SO2) at some time during its atmospheric lifetime. Since SO 2 is a primary component of the atmospheric sulfur cycle, quality measurements of this gas are important to understanding the cycling of sulfur through the atmosphere. The mixing ratio of SO2 in the atmosphere can be as low as a few 10's of parts-per-trillion by volume (pptv) in unpolluted areas and as high as 100's of parts-per-billion by volume (ppbv) near industrial centers. Obtaining SO2 measurements with mixing ratios that can differ by 105 in magnitude is a difficult task, especially for mixing ratios less than a few hundred pptv. The Diffusion Denuder/Sulfur Chemiluminescence Detector (DD/SCD) was developed further and tested in a rigorously blind comparison under controlled laboratory conditions. The DD/SCD exhibited excellent sensitivity and little-to-no interference from other trace gases. The DD/SCD performance was comparable to that of other state-of-the-art instruments developed for measuring SO 2 in the remote atmosphere. The Continuous SO2 Detector was developed to overcome the limitation of long sampling times (4 to 90 minutes) inherent in the DD/SCD and other state-of-the-art techniques. The Continuous SO2 Detector (CSD) was developed based on the design of the DD/SCD, but has been optimized for sensitive, high-time resolved measurements of SO2 in air. Sensitive, high-time resolved measurements would be beneficial for studying atmospheric SO2 over large geographical areas from a moving sampling platform such as an aircraft. The current prototype of the CSD is capable of measuring SO2 at mixing ratios of less than 100 pptv on the order of seconds. The DD/SCD, CSD and an automated, computer controlled dynamic dilution system described in this thesis represent a suite of instruments for the measurement of SO2 in the remote atmosphere.
• #### Characterization Of The Dat Zone, Eastern Alaska Range, Alaska: A Calcic Iron (Copper-Gold) Skarn Prospect

I studied a Cu-Fe-Au prospect in the eastern Alaska Range, Alaska, informally known as 'the DAT Zone'. Previous workers disagreed about the prospect's genesis; my work conclusively shows it to be a calcic iron skarn deposit with late quartz-pyrite-gold mineralization, broadly coeval with the host Pennsylvanian island arc-related volcanic and associated sedimentary rocks. A sericite-quartz-pyrite altered shear yields a $\sp{40}$Ar/$\sp{39}$Ar age similar to that of a nearby quartz monzodiorite pluton (300 Ma $\pm$ 1 Ma). The skarn consists of andradite extensively retrograded to ferrotremolite, quartz, magnetite, hematite, calcite, and chalcopyrite. Based on alteration pseudomorphs, the prograde assemblage was clinopyroxene with 20-40 %Hd, wollastonite, and andradite. The main-stage fluids were approximately 600$\sp\circ$C, moderately oxidized, and extremely saline ($>$60% NaCl equivalent). This fluid was clearly different from those of volcanogenic massive sulfide, metamorphic, or epithermal deposits. The lack of explosive textures is inconsistent with the DAT Zone as a porphyry copper deposit. <p>
• #### Putative pheromones in the urine of male moose: evolution of honest advertisement?

I tested hypotheses about how olfactory communication is related to mating behavior in Alaskan moose (Alces alces gigas). Males dig rutting pits where urine is deposited to which females strongly respond. Consequently, male urine may contain primer pheromones that synchronize estrus of females. Urine samples were collected from captive moose on the Kenai Peninsula, Alaska. Samples included those from the mating season and from the nonrutting period for two adult males, one yearling male, and one male and one female calf. After pH adjustment, samples were extracted with methylene chloride to yield 3 fractions (acidic, neutral, and basic), which were analyzed by gas chromatography-mass spectrometry. Putative pheromones include unsaturated alcohols and homologs of tetrahydro-6-methyl pyranone, and 2-nonen-4-one. I hypothesize that these compounds are related to hypophagia and catabolism of body reserves by rutting males, and thereby provide an honest advertisement of body condition in moose.
• #### Secondary reproductive strategies in Pacific black brant (Branta bernicla nigricans)

Waterfowl are known to use secondary reproductive strategies, both extra-pair copulations and intraspecific brood parasitism, to increase fitness. We used five polymorphic microsatellite loci to determine extra-pair paternity and nest parasitism in 30 nests of Pacific Black Brant geese (Branta bernicla nigricans) containing 108 offspring. Fourteen of the 30 nests contained offspring that were not genetically related to one or both of the attending adults: 6.5% (7/108) of the offspring resulted from extra-pair copulations (EPC); 13.9% (15/108) of the offspring resulted from intraspecific brood parasitism (IBP). All offspring resulting from EPCs were produced during the peak period of nest initiation. Adult females hosting parasitic eggs were significantly older than non-hosts. After accounting for eggs resulting from IBPs in the calculated clutch size, clutches containing IBPs were significantly smaller than unparasitized clutches. Our data indicate that secondary strategies represent an important component of reproductive effort in Black Brant.
• #### Ecology of mountain sheep: effects of mining and precipitation

We examined effects of mining on mountain sheep (Ovis canadensis nelsoni) in California. Size of home range, forage quality, and diet did not differ between populations in mined and nonmined areas. During summer, we observed the greatest disparity in time spent feeding and diet quality. Because of their dependence on a spring adjacent to the mine, sheep may have spent more time vigilant, and less time feeding. Reducing mining during summer may benefit sheep. We also compared ecology of two female mountain sheep populations from different areas (xeric vs. mesic) in the Mojave Desert. The more xeric Panamint Range was typified by more bare ground, less shrubs, less grass, and larger home ranges than at Old Dad Peak. Females from Old Dad foraged on grasses, whereas those from the Panamints consumed shrubs. We concluded that sheep from the Panamints required larger home ranges because of lower-quantity and quality of forage.
• #### Investigations into model systems of neurodegeneration: Organotypic brain slice culture and in vivo microdialysis

The mechanisms behind neurodegeneration in disease and injury have yet to be fully defined. Many in vitro and in vivo model systems, have been developed to investigate the mechanisms of neurotoxicity and its relation to human disease and injury. There are a few resounding connections between most types of neurological disorder; namely oxidative stress and inflammation. The glutamate receptor agonist, N-methyl-D-aspartate, can be used to imitate excitotoxicity during stroke as it overstimulates the glutamate receptor, leading to rises in intracellular calcium levels, which in turn lead to oxidative stress within the cell. Amyloid-beta protein (Abeta) a useful in many of its isoforms in creating in vitro model systems of Alzheimer's disease (AD). Abeta can directly cause the production of potentially harmful free radicals. This study investigates the formation of model systems of neurodegeneration: in vivo microdialysis and organotypic brain slices culture in order to assess the role of oxidative stress and inflammation morphologically and biochemically. The effect of melatonin, an endogenous antioxident, on oxidative stress associated with NMDA and Abeta neurotoxicity was determined through morphological analysis and biochemical markers of oxidative stress. This study reports that both NMDA and Abeta(25--35) cause oxidative stress in an organotypic brain slice culture model system of stroke and Alzheimer's disease as established by: (1) morphological analysis of tissue and ultrastructure, (2) redox-active assay, (3) heme-oxygenase assay, (4) 8-hydroxyguanosine assay and (5) interleukin IL-1beta and IL-6 assay (Abeta only) These investigations also demonstrate that melatonin can attenuate the oxidative stress associated with NMDA and Abeta exposure. These findings expand upon previous evidence from cell culture analysis of oxidative stress induced by NMDA and Abeta. Therefore, this evidence supports the theory that oxidative stress is involved in neurodegeneration in both excitotoxicity in stroke and in Abeta-mediated damage in Alzheimer's disease, and that endogenous antioxidant treatment may be a useful therapeutic approach in such injury and disease.
• #### Photosynthetic acclimation of white spruce (Picea glauca) to canopy microhabitats

Slow growing white spruce (Picea glauca) seedlings and saplings often become established early in succession and mature through several succession seres. During early succession, spruce often germinate in mineral soils and become established in alder (Alnus tenuifolia or A. crispa) thickets, with the potential for both competitive and facilitative relationships. Although competitive and facilitative plant interactions are often identified by changes in the growth or density of the interacting species, the result of the interaction will depend upon the individual plant's physiological acclimation to abiotic changes caused by neighboring plants. This study analyzes components of photosynthesis to provide information about the effects of alder on spruce. To isolate the responses of components of the photosynthetic process to neighbors, gas exchange techniques, needle chemical analysis, and observations of environmental parameters were utilized in growth chamber experiments, with individual plants in the field, and in controlled density plantations of alder and spruce. Growth at high light in all experiments resulted in lower maximum photosynthetic rates in current year shoots. Light response curves showed lower incident quantum yields in spruce seedlings growing at the high light levels typical on the floodplain. Increased soil nitrogen did not increase photosynthetic rates per gram needle in any of the experiments. However, increased seedling growth at high light in growth chamber experiments, and increased plant density in spruce/alder plantations, resulted in dilution of needle nitrogen. High needle nitrogen concentrations did not result in higher maximum net assimilation rates, although needle nitrogen was positively correlated with dark respiration rates. Concentrations of rubsico, a potentially rate limiting enzyme for photosynthesis at high light, was very responsive to changes in irradiance, but constituted only a small part of the needle nitrogen pool and did not appear to be limited by nitrogen availability. This work suggests that on a physiological level, spruce is a stress adapted plant with a low capacity to up-regulate photosynthetic physiological processes in response to increased light or nitrogen conditions.
• #### A toxicity assessment of total dissolved solid ions in mine effluent using two common bioassays: the 22-hour MicroTox assay and a S. carpricornutum growth assay

This research evaluated two microassays and a synthetic TDS standard to measure the effects of elevated TDS from mine effluent on biota of freshwater systems. Field samples from Red Dog and Fort Knox mines were tested on Selenastrum capricornutum and the MicroTox assay, and compared to the synthetic standard. Results indicate that the synthetic TDS standard is a poor representation of produced waters with similar total TDS concentrations. Additionally, no correlation was found between the toxicological responses of the two assays. Principle component analysis found the MicroTox assay to be most sensitive to cadmium and chloride. At concentrations present in the field samples, there does not appear to be a relationship between toxicity and TDS as measured on these assays.
• #### Distribution of hexachlorobenzene concentrations in spruce needle samples across Alaska

The global distribution of persistent organic pollutants has initiated considerable effort towards understanding long range atmospheric transport and partitioning of these potentially damaging compounds. Apparent latitude dependent concentration gradients of organic pollutants in otherwise pristine environments has given rise to a global fractionation model, coined the cold finger effect. According to the cold finger theory, semi-volatile persistent organic pollutant will show a preference for partitioning from the atmosphere to the ground and vegetation at northern latitudes. Here we present a study of hexachlorobenzene in spruce needle samples across Alaska, which offers a large range of climates, from its southern coastal rain forests to the northern arctic. The large variation in climate across Alaska should result in a measurable latitude dependent concentration gradient for HCB, if the cold finger effect is being realized. Spruce needle samples were extracted, cleaned, and analyzed by GC/MS. According to principle component regression analysis, HCB concentrations in all the spruce needle samples across Alaska show a strong positive correlation with lipid content of the needles. The HCB concentrations also show two distinct latitude trends. The spruce needle samples taken from the coast to approximately 63° north show relatively high HCB concentrations and a possible negative correlation with latitude. The samples between 63° and 68° north show a definite positive correlation between HCB concentration and latitude, which is consistent with the cold finger effect.
• #### Maximizing qiviut growth in muskoxen

Qiviut, the insulating underwool grown annually by muskoxen, is the basis of a successful knitting industry in Alaska. This study tested the hypothesis that the dietary sulfur-amino acid methionine could limit qiviut growth. Effects of commercial rumen-protected methionine supplements were measured in three experiments. In Experiment 1, emergent qiviut growth began in May and June, peaked in August and declined substantially by October. Three commercial methionine supplements were palatable and promoted fiber growth in subadult and adult muskoxen. In Experiment 2, the methionine supplement Smartamine promoted qiviut quality, growth, annual yield and strength. In a commercial enterprise, Experiment 3, Smartamine stimulated qiviut yield. For lactating muskoxen, qiviut responses were independent of nutrition, whereas effects on body weight and protein deposition were confined to females on a low plane of nutrition. It was concluded that addition of rumen-protected methionine to diets of farmed muskoxen can effectively promote qiviut production.
• #### Mechanism of impact and potential recovery of pigeon guillemots (Cepphus columba) after the Exxon Valdez oil spill

The abundance of pigeon guillemots in oiled areas of Prince William Sound, Alaska, failed to increase after the 1989 Exxon Valdez oil spill. Population growth may be constrained by the physiological effects of oil exposure, food availability, and nest predation." The author "conducted a comparative study among unoiled, oiled, and pre-spill data sets, to provide insight on factors limiting population recovery in oiled areas. Blood samples from chicks in oiled and unoiled areas provided little evidence of physiological effects of exposure to oil. Pigeon guillemot diet, productivity, growth rates, and fledging weights in unoiled areas of southwestern Prince William Sound from 1994 to 1998 indicate oiled areas had a lower proportion of high-lipid fish in the chick diet and lower fledging weights, compared to unoiled and pre-spill studies. These results suggest that the lack of recovery in oiled areas is associated with a prey base that results in lower fledging weights, which may reduce juvenile survival.
• #### Late Cenozoic unroofing sequence and foreland basin development of the central Alaska Range: implications from the Nenana Gravel

Facies architecture analysis, lithostratigraphy, and ⁴⁰AR/³⁹AR analyses of syn-orogenic sediments from the Nenana Gravel consistently demonstrate that deformation and erosion of the Late Cenozoic Alaska Range progressed in a foreland propagating sequence. Alluvial braidplain sediments, the oldest sourced from south of the present range divide, were shed into depozones exhibiting characteristics that indicate the growth of an underlying orogenic wedge primarily controlled deposition. Those characteristics include very immature and locally derived sediments, erosional unconformities, evidence for the competing influences of uplift and subsidence, lithology transitions that are correlated with facies transitions, and evidence for drainages that were defeated by surface uplift. Deposition of the Nenana Gravel took place between roughly 7 and 3 Ma. The Nenana Gravel depositional system changed when deformation within the proximal reaches of the basin brought resistant basement rocks to the surface forcing antecedent drainages to incise and abandon the alluvial braidplain they once fed.
• #### Seasonal movements of broad whitefish (Coregonus nasus) in the freshwater systems of the Prudhoe Bay oil field

Adult broad whitefish were tagged with radio transmitters in the Little Putuligayuk and Putuligayuk rivers along the Beaufort Sea coast of the Prudhoe Bay area, Alaska. Thirty-two fish were tagged in Lake Judith, a shallow tundra lake in the Little Putuligayuk River system. An additional 5 fish were tagged in the Putuligayuk River near a suspected spawning and overwintering site. Many fish left the tundra system to overwinter in the west channel of the Sagavanirktok River, however, unexpected movements also occurred. Six (20%) of the fish found in overwintering areas moved to the east channel of the Sagavanirktok River, an area long disregarded as having much potential for overwintering fish. Additionally, 2 fish traveled west over 100 km along the coast to the Colville River. Broad whitefish in this study wintered in marginal habitat and exhibited the ability to travel between distant coastal river systems along the arctic coast of Alaska.
• #### Population dynamics and ecology of yellow-cheeked voles (Microtus xanthognathus) in early post-fire seres of interior Alaska

Yellow-cheeked voles occupy early successional habitats in boreal regions, but specific factors influencing the species' distribution and population dynamics are not well known. Yellow-cheeked voles were studied in three early post-fire habitats in interior Alaska to relate population parameters to habitat characteristics. Voles were live-trapped during June, July, and August of 1997 and 1998, and habitat components were measured withing trapping grids. Capture data were analyzed using the robust design to estimate vole abundance, density, survival, and recruitment. Yellow-cheeked voles were most abundant in the floodplain white spruce, where survival was stable and recruitment was high. The white spruce habitat had the greatest cover of preferred forage species, while grasses, large diameter logs and snags provided escape cover. Observed differences in habitat quality may be related to unique successional processes in black and white spruces communities.