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• 701. [Article] Migration, movement, and habitat use of humpback whitefish (Coregonus pidschian) in the Copper River Delta, Alaska

  Research conducted on humpback whitefish Coregonus pidschian in the Copper River Delta, Alaska has revealed a complex life history involving seasonal migrations and the occupation of a variety of freshwater ...

  Citation × Citation Citation Abstract Copy Title: Migration, movement, and habitat use of humpback whitefish (Coregonus pidschian) in the Copper River Delta, Alaska Author: Neilson, Brian J. Research conducted on humpback whitefish Coregonus pidschian in the Copper River Delta, Alaska has revealed a complex life history involving seasonal migrations and the occupation of a variety of freshwater and marine habitats including lacustrine, riverine, estuarine, and marine. Forty-five whitefish were tagged with radio transmitters in 2006 and 2007, and another 29 whitefish were tagged with acoustic tags in 2008. In addition, otolith chemistry was used to evaluate marine habitat use of humpback whitefish sampled from McKinley Lake in the Copper River Delta, Alaska. Movements and migration of tagged fish were tracked using biotelemetry techniques from boats, airplanes, and fixed receiver stations throughout the spring, summer, and fall. Sagittal otoliths were extracted from 20 humpback whitefish and a chemical analysis was performed to evaluate levels of Sr:Ca. Biotelemetry and sampling results revealed seasonal migrations where humpback whitefish migrated into McKinley Lake in mid to late spring and left the lake by late summer and early fall. Fish migrated to the Copper River in the fall by traveling down Alaganik Slough and then to the Copper River by traveling through Pete Dahl Cutoff Slough or the Gulf of Alaska. Fish travel up the Copper River presumably to their spawning grounds. Nine tagged fish returned to McKinley Lake in 2007 and four tagged fish in 2008, indicating some fidelity to the summer feeding site. Otolith chemistry detected marine migrations in 45% of the samples. Three migratory behaviors were observed, while some individuals inhabited only freshwater environments, some individuals made single migrations to marine habitats, and other individuals made multiple migrations to marine habitats. Age of whitefish ranged from 2 to 9 years. Analysis of small-scale movement of humpback whitefish in McKinley Lake found movement rates to be significantly higher at dusk compared to night in one sampling period. However, diel movement activity in all other diel periods did not significantly differ, suggesting arrhythmic diel movement. A large portion of the lake was occupied at any given time, but not all areas were used equally. Activity levels, measured by change in zones, were variable between dates and indicated that fish often moved between detection zones. An increase in activity was observed in individuals 48 h prior to migration from the lake. This study provides the first documentation of migration, movement, and habitat use of humpback whitefish in the Copper River Delta, Alaska. Results of this study will help inform management of humpback whitefish in order to sustain populations into the future. This information should be considered in land use and species management planning in the Copper River basin including fish passage and harvest regulations. Title: Migration, movement, and habitat use of humpback whitefish (Coregonus pidschian) in the Copper River Delta, Alaska Author: Neilson, Brian J. Research conducted on humpback whitefish Coregonus pidschian in the Copper River Delta, Alaska has revealed a complex life history involving seasonal migrations and the occupation of a variety of freshwater and marine habitats including lacustrine, riverine, estuarine, and marine. Forty-five whitefish were tagged with radio transmitters in 2006 and 2007, and another 29 whitefish were tagged with acoustic tags in 2008. In addition, otolith chemistry was used to evaluate marine habitat use of humpback whitefish sampled from McKinley Lake in the Copper River Delta, Alaska. Movements and migration of tagged fish were tracked using biotelemetry techniques from boats, airplanes, and fixed receiver stations throughout the spring, summer, and fall. Sagittal otoliths were extracted from 20 humpback whitefish and a chemical analysis was performed to evaluate levels of Sr:Ca. Biotelemetry and sampling results revealed seasonal migrations where humpback whitefish migrated into McKinley Lake in mid to late spring and left the lake by late summer and early fall. Fish migrated to the Copper River in the fall by traveling down Alaganik Slough and then to the Copper River by traveling through Pete Dahl Cutoff Slough or the Gulf of Alaska. Fish travel up the Copper River presumably to their spawning grounds. Nine tagged fish returned to McKinley Lake in 2007 and four tagged fish in 2008, indicating some fidelity to the summer feeding site. Otolith chemistry detected marine migrations in 45% of the samples. Three migratory behaviors were observed, while some individuals inhabited only freshwater environments, some individuals made single migrations to marine habitats, and other individuals made multiple migrations to marine habitats. Age of whitefish ranged from 2 to 9 years. Analysis of small-scale movement of humpback whitefish in McKinley Lake found movement rates to be significantly higher at dusk compared to night in one sampling period. However, diel movement activity in all other diel periods did not significantly differ, suggesting arrhythmic diel movement. A large portion of the lake was occupied at any given time, but not all areas were used equally. Activity levels, measured by change in zones, were variable between dates and indicated that fish often moved between detection zones. An increase in activity was observed in individuals 48 h prior to migration from the lake. This study provides the first documentation of migration, movement, and habitat use of humpback whitefish in the Copper River Delta, Alaska. Results of this study will help inform management of humpback whitefish in order to sustain populations into the future. This information should be considered in land use and species management planning in the Copper River basin including fish passage and harvest regulations. Close

• 702. [Article] Effects of thinning on forest-floor vertebrates and analysis of habitat associations along ecological gradients in Oregon coastal Douglas-fir forests

  Thinning has the potential to increase structural diversity of managed forests for wildlife. During 1994-1996, I conducted experimental and observational studies using pitfall trapping to assess short-term ...

  Citation × Citation Citation Abstract Copy Title: Effects of thinning on forest-floor vertebrates and analysis of habitat associations along ecological gradients in Oregon coastal Douglas-fir forests Author: Suzuki, Nobuya Thinning has the potential to increase structural diversity of managed forests for wildlife. During 1994-1996, I conducted experimental and observational studies using pitfall trapping to assess short-term and potential long-term effects of thinning on abundance and reproduction of forest-floor vertebrates in Douglas-fir (Pseudotsuga menzeisii) forests of the Oregon Coast Range. Thinning had posititive effects on relative abundances of creeping voles (Microtus oregoni) and Pacific jumping mice (Zapus trinotatus) in both the short term and the long term. In contrast, relative abundance of western red-backed salamanders (Plethodon vehiculum) was lower in stands thinned 7-24 years previously than unthinned stands, suggesting potential negative effects of thinning in the long term. Relative abundance of western red-backed voles (Clethrionomys calfornicus) decreased within 2 years of thinning but was similar in stands thinned 7-24 years previously and unthinned stands. However, reproductive performance of western red-backed voles was higher in thinned than unthinned stands, suggesting potential positive effects of thinning on reproduction of the voles in the long term. In 1994, I investigated the influences of ecological gradients on habitat associations of forest-floor vertebrates at microsite and stand scales in 12 Douglas-fir stands in the stem exclusion stage. I examined various gradients of microclimate, stand structure, plant community composition, and downed wood. Among the ecological gradients I examined, the highest number of species was influenced by red alder/herb conifer/shrub gradient of community composition at both the microsite and stand scales. At the microsite scale, 7 species were associated with red alder/herb communities whereas only 2 species were associated with conifer/shrub communities. Red-alder patches with herb understory, therefore, have a potential role in maintaining biodiversity of forest-floor vertebrate communities in young Douglas-fir dominated stands. Furthermore, I found that habitat associations of 4 shrew species were generally consistent between the microsite and stand scales, whereas those of 3 rodent species were inconsistent between the 2 spatial scales. I hypothesized that this rodent-shrew dichotomy in habitat association occurring at the 2 spatial scales is a result of differences in their ability to explore habitats at multiple spatial scales. Title: Effects of thinning on forest-floor vertebrates and analysis of habitat associations along ecological gradients in Oregon coastal Douglas-fir forests Author: Suzuki, Nobuya Thinning has the potential to increase structural diversity of managed forests for wildlife. During 1994-1996, I conducted experimental and observational studies using pitfall trapping to assess short-term and potential long-term effects of thinning on abundance and reproduction of forest-floor vertebrates in Douglas-fir (Pseudotsuga menzeisii) forests of the Oregon Coast Range. Thinning had posititive effects on relative abundances of creeping voles (Microtus oregoni) and Pacific jumping mice (Zapus trinotatus) in both the short term and the long term. In contrast, relative abundance of western red-backed salamanders (Plethodon vehiculum) was lower in stands thinned 7-24 years previously than unthinned stands, suggesting potential negative effects of thinning in the long term. Relative abundance of western red-backed voles (Clethrionomys calfornicus) decreased within 2 years of thinning but was similar in stands thinned 7-24 years previously and unthinned stands. However, reproductive performance of western red-backed voles was higher in thinned than unthinned stands, suggesting potential positive effects of thinning on reproduction of the voles in the long term. In 1994, I investigated the influences of ecological gradients on habitat associations of forest-floor vertebrates at microsite and stand scales in 12 Douglas-fir stands in the stem exclusion stage. I examined various gradients of microclimate, stand structure, plant community composition, and downed wood. Among the ecological gradients I examined, the highest number of species was influenced by red alder/herb conifer/shrub gradient of community composition at both the microsite and stand scales. At the microsite scale, 7 species were associated with red alder/herb communities whereas only 2 species were associated with conifer/shrub communities. Red-alder patches with herb understory, therefore, have a potential role in maintaining biodiversity of forest-floor vertebrate communities in young Douglas-fir dominated stands. Furthermore, I found that habitat associations of 4 shrew species were generally consistent between the microsite and stand scales, whereas those of 3 rodent species were inconsistent between the 2 spatial scales. I hypothesized that this rodent-shrew dichotomy in habitat association occurring at the 2 spatial scales is a result of differences in their ability to explore habitats at multiple spatial scales. Close

• 703. [Article] Aquatic invertebrate-habitat relationships and stream channel cross section area change in response to streamside management zones in North Central Mississippi

  The southern states lead the country in timber production and are subject to Best Management Practices (BMPs) designed to mediate the effects of forest harvesting on water quality. Small headwater streams ...

  Citation × Citation Citation Abstract Copy Title: Aquatic invertebrate-habitat relationships and stream channel cross section area change in response to streamside management zones in North Central Mississippi Author: Luecker, Terry A. The southern states lead the country in timber production and are subject to Best Management Practices (BMPs) designed to mediate the effects of forest harvesting on water quality. Small headwater streams on timberland in North Central Mississippi have received little attention with respect to effectiveness of the BMPs designed to protect them. With stand rotations of 25-30 years and with some counties held in nearly 30% private industrial forestry ownership, impacts of intensive forest management on water resources have the potential to be large. In North Central Mississippi, I evaluated the effectiveness of Streamside Management Zones (SMZs), corridors of the riparian zone along the stream left unharvested, as a component of BMPs. The streams sampled were low-order perennial headwaters either within a clearcut with no SMZ, a clearcut with an SMZ, or a site that had not been harvested. Aquatic invertebrate community composition, habitat and substrate composition, and stream channel cross-section areas were evaluated in 2002 and again in 2003. My objectives were 1) to describe the invertebrates and habitat conditions at each site, 2) to determine if there are relationships between invertebrates and water quality, cover metrics, or relative amounts of substrate size fractions, and 3) to determine whether or not there were detectable treatment effects on either substrate composition or stream channel cross-section areas. Water quality, cover, and substrate size classes were highly variable within each harvest treatment. No significant differences were found downstream of harvest treatments for relative distribution of substrate within each harvest treatment group. Even though the habitat and substrate were highly variable, the invertebrate composition at many sites was dominated by a single family, Chironomidae. Ordinations of the presence of invertebrate taxa using non-metric multidimensional scaling showed a separation of the Reference and No-SMZ treatment groups for 2003, indicating that treatment effects may only be expressed in the biota and not in physical stream habitat characteristics measured by this study three to five years after harvesting. Changes in stream channel cross-section area occurred for all treatments, with Reference treatments degrading and SMZ and No-SMZ treatments aggrading between 24 and 29 months after harvesting treatments were established. Overall, No-SMZ treatments did not have significant changes in stream channel cross-section between sampling intervals, while Reference and SMZ treated streams changed significantly throughout the study. High natural variability of the streams made it difficult to discern differences in stream habitat parameters for each harvest treatment. Differences between Reference and No-SMZ sites in the 2003 ordinations and between No-SMZ and the other treatments for stream channel cross-sections indicated that SMZs are functioning in these low-order streams. Title: Aquatic invertebrate-habitat relationships and stream channel cross section area change in response to streamside management zones in North Central Mississippi Author: Luecker, Terry A. The southern states lead the country in timber production and are subject to Best Management Practices (BMPs) designed to mediate the effects of forest harvesting on water quality. Small headwater streams on timberland in North Central Mississippi have received little attention with respect to effectiveness of the BMPs designed to protect them. With stand rotations of 25-30 years and with some counties held in nearly 30% private industrial forestry ownership, impacts of intensive forest management on water resources have the potential to be large. In North Central Mississippi, I evaluated the effectiveness of Streamside Management Zones (SMZs), corridors of the riparian zone along the stream left unharvested, as a component of BMPs. The streams sampled were low-order perennial headwaters either within a clearcut with no SMZ, a clearcut with an SMZ, or a site that had not been harvested. Aquatic invertebrate community composition, habitat and substrate composition, and stream channel cross-section areas were evaluated in 2002 and again in 2003. My objectives were 1) to describe the invertebrates and habitat conditions at each site, 2) to determine if there are relationships between invertebrates and water quality, cover metrics, or relative amounts of substrate size fractions, and 3) to determine whether or not there were detectable treatment effects on either substrate composition or stream channel cross-section areas. Water quality, cover, and substrate size classes were highly variable within each harvest treatment. No significant differences were found downstream of harvest treatments for relative distribution of substrate within each harvest treatment group. Even though the habitat and substrate were highly variable, the invertebrate composition at many sites was dominated by a single family, Chironomidae. Ordinations of the presence of invertebrate taxa using non-metric multidimensional scaling showed a separation of the Reference and No-SMZ treatment groups for 2003, indicating that treatment effects may only be expressed in the biota and not in physical stream habitat characteristics measured by this study three to five years after harvesting. Changes in stream channel cross-section area occurred for all treatments, with Reference treatments degrading and SMZ and No-SMZ treatments aggrading between 24 and 29 months after harvesting treatments were established. Overall, No-SMZ treatments did not have significant changes in stream channel cross-section between sampling intervals, while Reference and SMZ treated streams changed significantly throughout the study. High natural variability of the streams made it difficult to discern differences in stream habitat parameters for each harvest treatment. Differences between Reference and No-SMZ sites in the 2003 ordinations and between No-SMZ and the other treatments for stream channel cross-sections indicated that SMZs are functioning in these low-order streams. Close

• 704. [Article] How the animals found their places : pattern detection, experimentation, and epistemology in a high desert stream fish assemblage

  I examined the relative roles of biotic and abiotic factors in structuring redband trout Oncorhynchus mykiss distributions in the South Fork John Day. I first examined the relationship between the biological ...

  Citation × Citation Citation Abstract Copy Title: How the animals found their places : pattern detection, experimentation, and epistemology in a high desert stream fish assemblage Author: White, Seth Michael I examined the relative roles of biotic and abiotic factors in structuring redband trout Oncorhynchus mykiss distributions in the South Fork John Day. I first examined the relationship between the biological traits of the fish assemblage and riparian-geomorphic features in context of prevailing theories of stream ecology stemming from the river continuum concept (Chapter 2). I found that fish traits and habitat characteristics were related to one another in a different manner according to the spatial scale of observation (watershed, tributary, and reach scales) and that mode of species coexistence (niche overlap, niche partitioning, and non-associative) was correlated more strongly with the distribution of traits than with environmental features, suggesting that biotic interactions play an important role in structuring the fish assemblage. Next, I described the 'behaviorscape' of redband trout foraging and aggression in context of prevailing foraging theory (Chapter 3, Part I). I found that redband trout behaviors could be described in terms of expected energetic gains and losses and potentially predation risk, with 'risky' behaviors yielding higher expected energetic gains in habitats with abundant structural refugia. These findings raised the questions of how fish growth and foraging behavior would be affected by increased food resources, questions which I addressed via a supplemental feeding experiment in two streams (Chapter 3, Part II). I observed nearly an order of magnitude increase in instantaneous growth rates of redband trout O. mykiss and a potential competitor, juvenile Chinook salmon O. tshawytscha, upon feeding, demonstrating that food is a limiting factor for salmonid growth in this system. Also upon feeding, redband trout foraging and aggression increased in a stream with no heterospecifics, lower discharge, and colder water temperature, but not in a stream with the opposite characteristics. These findings suggested that O. mykiss and O. tshawytscha may coexist in a state of interactive segregation, contrary to the common wisdom that the two species are selectively segregated and have therefore evolved fully-distinct habitat preferences. To acquire further evidence for this hypothesis and to elucidate the role of competitor densities on habitat selection at local scales (which would in turn affect fish distribution patterns at larger scales), I employed a multi-species habitat selection model (Chapter 4). Redband trout habitat selection of enriched patches was negatively affected by conspecific densities as expected, but positively affected by juvenile Chinook densities, a finding that I attribute to habitat effects or heterospecific attraction. Redband trout foraging and aggression decreased in the presence of both conspecifics and heterospecifics, and aggression appeared to decrease with supplemental feeding. These contrary results between the former and latter experiments testing for aggression as a response to feeding are explained via the manner in which food was delivered to the stream, pulsed at dawn and dusk versus delivered evenly over time, respectively. In the concluding chapter (Chapter 5), I make the case that restoration practices acknowledging a broad range of potential drivers for species distributions—including behaviorally-mediated biotic interactions among the fish assemblage—will better serve a broader range of restoration goals. Title: How the animals found their places : pattern detection, experimentation, and epistemology in a high desert stream fish assemblage Author: White, Seth Michael I examined the relative roles of biotic and abiotic factors in structuring redband trout Oncorhynchus mykiss distributions in the South Fork John Day. I first examined the relationship between the biological traits of the fish assemblage and riparian-geomorphic features in context of prevailing theories of stream ecology stemming from the river continuum concept (Chapter 2). I found that fish traits and habitat characteristics were related to one another in a different manner according to the spatial scale of observation (watershed, tributary, and reach scales) and that mode of species coexistence (niche overlap, niche partitioning, and non-associative) was correlated more strongly with the distribution of traits than with environmental features, suggesting that biotic interactions play an important role in structuring the fish assemblage. Next, I described the 'behaviorscape' of redband trout foraging and aggression in context of prevailing foraging theory (Chapter 3, Part I). I found that redband trout behaviors could be described in terms of expected energetic gains and losses and potentially predation risk, with 'risky' behaviors yielding higher expected energetic gains in habitats with abundant structural refugia. These findings raised the questions of how fish growth and foraging behavior would be affected by increased food resources, questions which I addressed via a supplemental feeding experiment in two streams (Chapter 3, Part II). I observed nearly an order of magnitude increase in instantaneous growth rates of redband trout O. mykiss and a potential competitor, juvenile Chinook salmon O. tshawytscha, upon feeding, demonstrating that food is a limiting factor for salmonid growth in this system. Also upon feeding, redband trout foraging and aggression increased in a stream with no heterospecifics, lower discharge, and colder water temperature, but not in a stream with the opposite characteristics. These findings suggested that O. mykiss and O. tshawytscha may coexist in a state of interactive segregation, contrary to the common wisdom that the two species are selectively segregated and have therefore evolved fully-distinct habitat preferences. To acquire further evidence for this hypothesis and to elucidate the role of competitor densities on habitat selection at local scales (which would in turn affect fish distribution patterns at larger scales), I employed a multi-species habitat selection model (Chapter 4). Redband trout habitat selection of enriched patches was negatively affected by conspecific densities as expected, but positively affected by juvenile Chinook densities, a finding that I attribute to habitat effects or heterospecific attraction. Redband trout foraging and aggression decreased in the presence of both conspecifics and heterospecifics, and aggression appeared to decrease with supplemental feeding. These contrary results between the former and latter experiments testing for aggression as a response to feeding are explained via the manner in which food was delivered to the stream, pulsed at dawn and dusk versus delivered evenly over time, respectively. In the concluding chapter (Chapter 5), I make the case that restoration practices acknowledging a broad range of potential drivers for species distributions—including behaviorally-mediated biotic interactions among the fish assemblage—will better serve a broader range of restoration goals. Close

• 705. [Article] Spatial heterogeneity, meta-analysis and spatial dependence : three essays on environmental valuation and spatial land management decisions

  This dissertation consists of three essays that collectively address the importance of accounting for spatial heterogeneity and spatial dependence of environmental assets and natural resources in policy ...

  Citation × Citation Citation Abstract Copy Title: Spatial heterogeneity, meta-analysis and spatial dependence : three essays on environmental valuation and spatial land management decisions Author: Bu, Meidan This dissertation consists of three essays that collectively address the importance of accounting for spatial heterogeneity and spatial dependence of environmental assets and natural resources in policy making. The first essay examines the value of different wetland ecosystem services using an expanded meta-dataset of valuation studies in North America. The purpose of this essay is to explore the sources of variation in wetland values from valuation methodology, ecosystem functions, and site-specific geographic, demographic and socio-economic characteristics. This essay used panel random effect models stratified "by study", "by state" and "by wetland site" to address the issues of correlation between wetland value estimates. Results indicated that wetland welfare measures reported by the same study and in the same wetland site are correlated. By comparing regression results and conclusions from this study with two internationally scoped meta-analysis studies, this essay found that the wetland valuation literature is not robust to regional characteristics, and wetland welfare estimates are sensitive to geographic extent. The second essay extends the first essay to investigate spatial spillover effects of wetland welfare estimates in North America. The primary purpose of the essay is to explore whether wetland values are correlated across space and what determines the correlation. The goal is accomplished by incorporating spatial econometric methods into the meta-analysis framework. The essay constructed three spatial weight matrices based on threshold distances, the ecological similarity and the economic similarity of wetland sites in the metadata. Results indicate that spatial proximity is an important predictor of wetland values regardless of wetland type and function. In part this is captured through shared contexts including resource availability and market characteristics. However, similar ecological and economic profiles are insufficient to capture shared values when transferring value estimates across spatial areas. Results from this study also raised questions on whether ecological functions and economic markets are sufficient for improving international transfers when studies are beyond geographic thresholds. The third essay incorporates spatial econometric models into a stochastic optimization framework to explore the consequences of ignoring the spatial linkage of management units in land management outcomes. The integrated framework combines an economic decision model, a spatial fire simulation model, a spotted owl population prediction model to maximize the expected post-fire and post-treatment NSO population under a budget constraint. Results from this essay inform us that ignoring spatial habitat connections leads to an underestimate of the fuel treatment disturbance and an over-estimate of the expected post-fire and post-treatment NSO population. However, the negative externality of habitat conversions depends on the degree of habitat connections. Additionally, the amount of total treatment area depends on the degree of habitat connections. The optimization outcome suggests less fuel treatment for a landscape with a higher degree of habitat connections. Moreover, the optimization outcome informs us that the spatial configuration of fuel treatment matters for the NSO population protection. Ignoring the spatial habitat connections leads to a fragmented treatment pattern and fails to protect the core NSO habitat from treatment disturbances. Title: Spatial heterogeneity, meta-analysis and spatial dependence : three essays on environmental valuation and spatial land management decisions Author: Bu, Meidan This dissertation consists of three essays that collectively address the importance of accounting for spatial heterogeneity and spatial dependence of environmental assets and natural resources in policy making. The first essay examines the value of different wetland ecosystem services using an expanded meta-dataset of valuation studies in North America. The purpose of this essay is to explore the sources of variation in wetland values from valuation methodology, ecosystem functions, and site-specific geographic, demographic and socio-economic characteristics. This essay used panel random effect models stratified "by study", "by state" and "by wetland site" to address the issues of correlation between wetland value estimates. Results indicated that wetland welfare measures reported by the same study and in the same wetland site are correlated. By comparing regression results and conclusions from this study with two internationally scoped meta-analysis studies, this essay found that the wetland valuation literature is not robust to regional characteristics, and wetland welfare estimates are sensitive to geographic extent. The second essay extends the first essay to investigate spatial spillover effects of wetland welfare estimates in North America. The primary purpose of the essay is to explore whether wetland values are correlated across space and what determines the correlation. The goal is accomplished by incorporating spatial econometric methods into the meta-analysis framework. The essay constructed three spatial weight matrices based on threshold distances, the ecological similarity and the economic similarity of wetland sites in the metadata. Results indicate that spatial proximity is an important predictor of wetland values regardless of wetland type and function. In part this is captured through shared contexts including resource availability and market characteristics. However, similar ecological and economic profiles are insufficient to capture shared values when transferring value estimates across spatial areas. Results from this study also raised questions on whether ecological functions and economic markets are sufficient for improving international transfers when studies are beyond geographic thresholds. The third essay incorporates spatial econometric models into a stochastic optimization framework to explore the consequences of ignoring the spatial linkage of management units in land management outcomes. The integrated framework combines an economic decision model, a spatial fire simulation model, a spotted owl population prediction model to maximize the expected post-fire and post-treatment NSO population under a budget constraint. Results from this essay inform us that ignoring spatial habitat connections leads to an underestimate of the fuel treatment disturbance and an over-estimate of the expected post-fire and post-treatment NSO population. However, the negative externality of habitat conversions depends on the degree of habitat connections. Additionally, the amount of total treatment area depends on the degree of habitat connections. The optimization outcome suggests less fuel treatment for a landscape with a higher degree of habitat connections. Moreover, the optimization outcome informs us that the spatial configuration of fuel treatment matters for the NSO population protection. Ignoring the spatial habitat connections leads to a fragmented treatment pattern and fails to protect the core NSO habitat from treatment disturbances. Close

• 706. [Article] A comparison of seafloor sonar classification methods through the use of error matrices and 3 dimensional GIS visualization : a multibeam sonar investigation of Nehalem Bank, Oregon

  Multibeam sonar data was collected on Nehalem Bank, off of the Oregon Coast with the purpose of increasing the spatial resolution of our knowledge of the area and delineating seafloor habitats. The system ...

  Citation × Citation Citation Abstract Copy Title: A comparison of seafloor sonar classification methods through the use of error matrices and 3 dimensional GIS visualization : a multibeam sonar investigation of Nehalem Bank, Oregon Author: Lanier, Andrew S. Multibeam sonar data was collected on Nehalem Bank, off of the Oregon Coast with the purpose of increasing the spatial resolution of our knowledge of the area and delineating seafloor habitats. The system used was the Kongsberg Simrad EM-300 operating at 30 kHz. The data set collected includes both topographic and backscatter information, both of which were processed and gridded at a 5m cell-size resolution. This thesis summarizes the methods used in the characterization of seafloor habitat using the Nehalem Bank data and the analysis tools incorporated within a geographic information system (GIS). This work focuses on investigations into the analysis of benthic habitats through the use of algorithmic calculations at multiple scales to quantitatively delineate distinct seafloor regions. A recently developed spatial analysis technique, the bathymetric position index (BPI), was tested and used as part of the Benthic Terrain Modeler Tool to classify the Nehalem Bank data. Those results were compared both qualitatively and quantitatively to a newly developed method (developed for this project) entitled the surface interpretation method (SIM). Both methods of classification use multiple scales of BPI in conjunction with the topographic digital elevation model (DEM) to quantitatively delineate seafloor habitats. While accuracy assessments of remotely sensed imagery on land are usually carried out using groundtruthing information collected specifically for that purpose, sonar imagery is often assessed using any information available. The groundtruth data available for Nehalem Bank is sparsely located throughout the region and includes: submersible dives, sample data, and seismic and sidescan imagery. In order to evaluate the fit of the classification attempts to the DEM quantitatively, a set of reference points was created and interpreted using the three dimensional (3D) visualization capabilities of a GIS. The results were analyzed using error matrix statistical measures that provided a quantitative assessment of the classification results, the feedback from which guided a refinement of the classification methods. This was done in attempt to optimize “real-world” evaluation of a classification methods results, without an idealized level of seafloor groundtruth data. The backscatter component of the data was processed to reduce the influence of grazing angle on the intensity of surface returns, a common source of noise that dominates many datasets. The processed image shows a reduced variability of the grey level of the imagery in both along and across track directions. Submersible dive groundtruth data were then co-located with the backscatter imagery using habitat interpretations of the dives displayed upon the DEM. The backscatter data was then classified in the regions of the dives using textural analysis with grey level co-occurrence matrix derived indices of homogeneity and entropy. The resulting substrate class divisions satisfactorily parsed the landscape into habitat regions, with the exceptions of the nadir and shadow regions. However, higher frequency deep-towed sidescan imagery in the same region shows that the delineation of substrate regions appears to be incorrect with the EM300 imagery likely imaging subsurface seafloor characteristics. Title: A comparison of seafloor sonar classification methods through the use of error matrices and 3 dimensional GIS visualization : a multibeam sonar investigation of Nehalem Bank, Oregon Author: Lanier, Andrew S. Multibeam sonar data was collected on Nehalem Bank, off of the Oregon Coast with the purpose of increasing the spatial resolution of our knowledge of the area and delineating seafloor habitats. The system used was the Kongsberg Simrad EM-300 operating at 30 kHz. The data set collected includes both topographic and backscatter information, both of which were processed and gridded at a 5m cell-size resolution. This thesis summarizes the methods used in the characterization of seafloor habitat using the Nehalem Bank data and the analysis tools incorporated within a geographic information system (GIS). This work focuses on investigations into the analysis of benthic habitats through the use of algorithmic calculations at multiple scales to quantitatively delineate distinct seafloor regions. A recently developed spatial analysis technique, the bathymetric position index (BPI), was tested and used as part of the Benthic Terrain Modeler Tool to classify the Nehalem Bank data. Those results were compared both qualitatively and quantitatively to a newly developed method (developed for this project) entitled the surface interpretation method (SIM). Both methods of classification use multiple scales of BPI in conjunction with the topographic digital elevation model (DEM) to quantitatively delineate seafloor habitats. While accuracy assessments of remotely sensed imagery on land are usually carried out using groundtruthing information collected specifically for that purpose, sonar imagery is often assessed using any information available. The groundtruth data available for Nehalem Bank is sparsely located throughout the region and includes: submersible dives, sample data, and seismic and sidescan imagery. In order to evaluate the fit of the classification attempts to the DEM quantitatively, a set of reference points was created and interpreted using the three dimensional (3D) visualization capabilities of a GIS. The results were analyzed using error matrix statistical measures that provided a quantitative assessment of the classification results, the feedback from which guided a refinement of the classification methods. This was done in attempt to optimize “real-world” evaluation of a classification methods results, without an idealized level of seafloor groundtruth data. The backscatter component of the data was processed to reduce the influence of grazing angle on the intensity of surface returns, a common source of noise that dominates many datasets. The processed image shows a reduced variability of the grey level of the imagery in both along and across track directions. Submersible dive groundtruth data were then co-located with the backscatter imagery using habitat interpretations of the dives displayed upon the DEM. The backscatter data was then classified in the regions of the dives using textural analysis with grey level co-occurrence matrix derived indices of homogeneity and entropy. The resulting substrate class divisions satisfactorily parsed the landscape into habitat regions, with the exceptions of the nadir and shadow regions. However, higher frequency deep-towed sidescan imagery in the same region shows that the delineation of substrate regions appears to be incorrect with the EM300 imagery likely imaging subsurface seafloor characteristics. Close

• 707. [Article] The seasonal occurence and larval habitats of the mosquitoes of Corvallis, Oregon (Diptera-Culicidae)

  From May through November 1963, a mosquito survey was made in the city of Corvallis, Oregon. The information obtained dealt with the species of mosquitoes found, their seasonal occurrence and the location ...

  Citation × Citation Citation Abstract Copy Title: The seasonal occurence and larval habitats of the mosquitoes of Corvallis, Oregon (Diptera-Culicidae) Author: Kerr, George Ezekiel From May through November 1963, a mosquito survey was made in the city of Corvallis, Oregon. The information obtained dealt with the species of mosquitoes found, their seasonal occurrence and the location and nature of their larval habitats. A quantitative and qualitative analysis of larval and adult mosquito collections by genera and species was used to determine seasonal occurrence and distribution. Results reported here are based on a total of 309 light trap collections made in six locations, 29 aspirator collections made in each of 11 diurnal resting sites and larval surveys which were made every 10 days using the dipper method. During the course of the survey 6,968 specimens comprising nine species and four genera were collected. The species in order of abundance were Culex pipiens, Culex pens, Culex tarsalis, Culiseta incidens, Aedes increpitus, Culiseta inornata, Anopheles punctipennis, Aedes vexans and Aedes sierrensis. With the exception of Culiseta inornata, a seasonal variation in abundance of all the species favoring the late summer and early fall was observed. Culiseta inornata was common during the spring and early fall when temperatures were cooler. Individual collecting techniques did not provide an accurate, quantitative comparison of the relative abundance of all the species. On many occasions when weather conditions were ideal for mosquito activity, the number of specimens that were taken in light trap collections were not a true representative of the numbers present in the vicinity. Culex pipiens and Culex tarsalis were taken in large numbers in light trap collections but Aedes sierrensis and Anopheles punctipennis were not present in large enough numbers to indicate population trends. Conversely, collections in diurnal resting sites included large numbers of Culiseta incidens but very few Culiseta inornata. The results of light trap catches however, corresponded closely with catches in diurnal resting sites as far as qualitative studies were concerned. Routine larval collections from common breeding habitats around the city were positive for all species except Aedes vexans, Aedes increpitus and Aedes sierrensis. These positive collections always confirmed the quantitative adult catches. The presence of the Aedes species in the collections was probably due to adult infiltration from breeding areas outside the city. Larval habitats of the immature mosquitoes collected were divided into two ecological groups. First, temporary bodies of water which include rain pools, water troughs and concrete structures and second, permanent bodies of water including log ponds and sewage disposal ponds. All these habitats gave rise to a number of generations during the mosquito breeding season. Mosquitoes collected from temporary habitats included Culex pipiens and Culiseta incidens while Culex tarsalis, Culex pens, Anopheles punctipennis and Culiseta inornata were abundant in permanent habitats. Title: The seasonal occurence and larval habitats of the mosquitoes of Corvallis, Oregon (Diptera-Culicidae) Author: Kerr, George Ezekiel From May through November 1963, a mosquito survey was made in the city of Corvallis, Oregon. The information obtained dealt with the species of mosquitoes found, their seasonal occurrence and the location and nature of their larval habitats. A quantitative and qualitative analysis of larval and adult mosquito collections by genera and species was used to determine seasonal occurrence and distribution. Results reported here are based on a total of 309 light trap collections made in six locations, 29 aspirator collections made in each of 11 diurnal resting sites and larval surveys which were made every 10 days using the dipper method. During the course of the survey 6,968 specimens comprising nine species and four genera were collected. The species in order of abundance were Culex pipiens, Culex pens, Culex tarsalis, Culiseta incidens, Aedes increpitus, Culiseta inornata, Anopheles punctipennis, Aedes vexans and Aedes sierrensis. With the exception of Culiseta inornata, a seasonal variation in abundance of all the species favoring the late summer and early fall was observed. Culiseta inornata was common during the spring and early fall when temperatures were cooler. Individual collecting techniques did not provide an accurate, quantitative comparison of the relative abundance of all the species. On many occasions when weather conditions were ideal for mosquito activity, the number of specimens that were taken in light trap collections were not a true representative of the numbers present in the vicinity. Culex pipiens and Culex tarsalis were taken in large numbers in light trap collections but Aedes sierrensis and Anopheles punctipennis were not present in large enough numbers to indicate population trends. Conversely, collections in diurnal resting sites included large numbers of Culiseta incidens but very few Culiseta inornata. The results of light trap catches however, corresponded closely with catches in diurnal resting sites as far as qualitative studies were concerned. Routine larval collections from common breeding habitats around the city were positive for all species except Aedes vexans, Aedes increpitus and Aedes sierrensis. These positive collections always confirmed the quantitative adult catches. The presence of the Aedes species in the collections was probably due to adult infiltration from breeding areas outside the city. Larval habitats of the immature mosquitoes collected were divided into two ecological groups. First, temporary bodies of water which include rain pools, water troughs and concrete structures and second, permanent bodies of water including log ponds and sewage disposal ponds. All these habitats gave rise to a number of generations during the mosquito breeding season. Mosquitoes collected from temporary habitats included Culex pipiens and Culiseta incidens while Culex tarsalis, Culex pens, Anopheles punctipennis and Culiseta inornata were abundant in permanent habitats. Close

• 708. [Article] Ecology of breeding mallards : nest parasitism; brood survival; and habitat utilization

  In 1976 and 1977 I examined three broad problems associated with the recruitment of young mallards, Anas platyrhynchos, in the Prairie Pothole Region of North Dakota. The three problems studied were: the ...

  Citation × Citation Citation Abstract Copy Title: Ecology of breeding mallards : nest parasitism; brood survival; and habitat utilization Author: Talent, Larry Gene In 1976 and 1977 I examined three broad problems associated with the recruitment of young mallards, Anas platyrhynchos, in the Prairie Pothole Region of North Dakota. The three problems studied were: the effects of interspecific nest parasitism on production; the chronology and magnitude of total-brood loss during the brood-rearing period; and, mobility, home range, and habitat utilization of broods. Nest parasitism occurred only in mallard nests that were in marsh habitat. Of 24 active mallard nests located in marsh habitat during 1976, 46% were parasitized. Forty-two percent were parasitized by redheads, Aythya americana, and 8% by ruddy ducks, Oxyura jamaicensis. Only three mallard nests were found in marsh habitat in 1977, presumably because of a severe drought, and none were parasitized. Nest parasitism by redheads or ruddy ducks did not significantly decrease mallard nest success (P>0.05). Parasitism by redheads reduced mallard clutch-size by about 1.5 eggs; parasitism by ruddy ducks had no significant effect on mallard clutch-size. In successful nests, nest parasitism by redheads significantly reduced mallard egg success (P<0.05), primarily through host egg displacement. Due to a small sample size, the effect nest parasitism by. ruddy ducks had on mallard egg success was not determined. Nest parasitism by redheads could potentially reduce the number of mallards produced in the Prairie Pothole Region during some years. Survival of mallard broods was estimated from data obtained from 25 radio-marked broods monitored during 1976 and 1977. Radio-equipped mallard hens fledged at least one duckling in 44% of broods initially hatched in 1976 and 55% in 1977. Combined brood survival for 1976 and 1977 was 48%. Eighty-five percent of the loss of entire broods occurred within the first two weeks after hatching and all losses occurred in wetlands. Few ducklings and no broods were lost during overland travel. The primary predators on ducklings in wetlands were mink, Mustela vison. Mallard broods were quite mobile during the first few weeks after hatching, but mobility varied greatly between 1976 and 1977. Of 16 broods monitored in 1976, 12 made major overland moves among wetlands and utilized from 2 to 10 different wetlands during the brood-rearing period. In 1977 only 2 of 9 radio-marked broods made major habitat shifts. The reason for the difference in brood mobility between 1976 and 1977 appeared to be related to drought conditions. The area of the corrected 'home range of radio-marked broods increased rapidly until broods were about one week old; by two weeks the home range of most broods was stable. Cumulative home ranges varied among broods but averaged 11.0±4.7 ha (mean±SD). Broods used only a small portion of the home range in any one week period. Generally, the home range of a brood on a particular wetland ranged in size from 4 to 6 ha. Habitats utilized by broods varied greatly between 1976 and 1977. In 1976, when many types of wetlands contained water, mallard hens with broods demonstrated a significant preference for whitetop ponds, but rejection was indicated for other types of seasonal wetlands. In 1976 overall use of semipermanent wetlands was significantly less than expected; but in 1977, when drought conditions prevailed on the study area, semipermanent wetlands were used by mallard broods directly in proportion to their availability. Mallard hens with broods used brood-rearing areas with high standing crops of benthic invertebrates. Title: Ecology of breeding mallards : nest parasitism; brood survival; and habitat utilization Author: Talent, Larry Gene In 1976 and 1977 I examined three broad problems associated with the recruitment of young mallards, Anas platyrhynchos, in the Prairie Pothole Region of North Dakota. The three problems studied were: the effects of interspecific nest parasitism on production; the chronology and magnitude of total-brood loss during the brood-rearing period; and, mobility, home range, and habitat utilization of broods. Nest parasitism occurred only in mallard nests that were in marsh habitat. Of 24 active mallard nests located in marsh habitat during 1976, 46% were parasitized. Forty-two percent were parasitized by redheads, Aythya americana, and 8% by ruddy ducks, Oxyura jamaicensis. Only three mallard nests were found in marsh habitat in 1977, presumably because of a severe drought, and none were parasitized. Nest parasitism by redheads or ruddy ducks did not significantly decrease mallard nest success (P>0.05). Parasitism by redheads reduced mallard clutch-size by about 1.5 eggs; parasitism by ruddy ducks had no significant effect on mallard clutch-size. In successful nests, nest parasitism by redheads significantly reduced mallard egg success (P<0.05), primarily through host egg displacement. Due to a small sample size, the effect nest parasitism by. ruddy ducks had on mallard egg success was not determined. Nest parasitism by redheads could potentially reduce the number of mallards produced in the Prairie Pothole Region during some years. Survival of mallard broods was estimated from data obtained from 25 radio-marked broods monitored during 1976 and 1977. Radio-equipped mallard hens fledged at least one duckling in 44% of broods initially hatched in 1976 and 55% in 1977. Combined brood survival for 1976 and 1977 was 48%. Eighty-five percent of the loss of entire broods occurred within the first two weeks after hatching and all losses occurred in wetlands. Few ducklings and no broods were lost during overland travel. The primary predators on ducklings in wetlands were mink, Mustela vison. Mallard broods were quite mobile during the first few weeks after hatching, but mobility varied greatly between 1976 and 1977. Of 16 broods monitored in 1976, 12 made major overland moves among wetlands and utilized from 2 to 10 different wetlands during the brood-rearing period. In 1977 only 2 of 9 radio-marked broods made major habitat shifts. The reason for the difference in brood mobility between 1976 and 1977 appeared to be related to drought conditions. The area of the corrected 'home range of radio-marked broods increased rapidly until broods were about one week old; by two weeks the home range of most broods was stable. Cumulative home ranges varied among broods but averaged 11.0±4.7 ha (mean±SD). Broods used only a small portion of the home range in any one week period. Generally, the home range of a brood on a particular wetland ranged in size from 4 to 6 ha. Habitats utilized by broods varied greatly between 1976 and 1977. In 1976, when many types of wetlands contained water, mallard hens with broods demonstrated a significant preference for whitetop ponds, but rejection was indicated for other types of seasonal wetlands. In 1976 overall use of semipermanent wetlands was significantly less than expected; but in 1977, when drought conditions prevailed on the study area, semipermanent wetlands were used by mallard broods directly in proportion to their availability. Mallard hens with broods used brood-rearing areas with high standing crops of benthic invertebrates. Close

• 709. [Article] Response of juvenile steelhead trout to an instream habitat rehabilitation project in Meadow Creek, Oregon

  Responses of juvenile steelhead trout to changes in stream habitat resulting from an instream habitat rehabilitation project in Meadow Creek, Oregon were measured from 1991 through 1992 and compared to ...

  Citation × Citation Citation Abstract Copy Title: Response of juvenile steelhead trout to an instream habitat rehabilitation project in Meadow Creek, Oregon Author: Miller, Alan Christopher Responses of juvenile steelhead trout to changes in stream habitat resulting from an instream habitat rehabilitation project in Meadow Creek, Oregon were measured from 1991 through 1992 and compared to pre-treatment data from 1987 through 1990. Sixty nine pool-forming, and 59 channel-stabilizing log structures were constructed by the U.S. Forest Service in a 3.7 km reach in 1990. A 20-year flood caused extensive modifications to the instream structures in May 1991. Pool habitat and large wood volume increased in the treatment and the two reference reaches but pool development was greater in the treatment reach compared to the two reference reaches. Summer rearing densities of juvenile steelhead were similar for the treatment and the two reference reaches at the reach scale. Summer rearing densities were lower in the post-treatment period compared to the pre-treatment period for the treatment and two reference reaches. Mean density of juvenile steelhead was higher in complex pools compared to non-complex pools throughout the study area. Mean density of juvenile steelhead was higher in pools associated with large wood from washed-out structures compared to pools associated with intact structures in the treatment reach. Changes in smolt production from the treatment reach following the rehabilitation project could not be determined due to trapping difficulties. Only three percent of the smolts emigrating from the basin overwintered in the treatment reach in 1992. Four life history patterns of juvenile steelhead were identified. Only one of the four life history patterns rears in the Meadow Creek basin until smolting. From these findings I conclude that the instream habitat rehabilitation project did not increase the abundance of juvenile steelhead or smolt production during the first two years after treatment. An extended drought and a 20-year flood may have been the dominant factors controlling abundance of juvenile steelhead over the study period. The Meadow Creek rehabilitation project may have limited success at increasing smolt production because it influences only one of four life history patterns of juvenile steelhead during the entire freshwater rearing phase. Title: Response of juvenile steelhead trout to an instream habitat rehabilitation project in Meadow Creek, Oregon Author: Miller, Alan Christopher Responses of juvenile steelhead trout to changes in stream habitat resulting from an instream habitat rehabilitation project in Meadow Creek, Oregon were measured from 1991 through 1992 and compared to pre-treatment data from 1987 through 1990. Sixty nine pool-forming, and 59 channel-stabilizing log structures were constructed by the U.S. Forest Service in a 3.7 km reach in 1990. A 20-year flood caused extensive modifications to the instream structures in May 1991. Pool habitat and large wood volume increased in the treatment and the two reference reaches but pool development was greater in the treatment reach compared to the two reference reaches. Summer rearing densities of juvenile steelhead were similar for the treatment and the two reference reaches at the reach scale. Summer rearing densities were lower in the post-treatment period compared to the pre-treatment period for the treatment and two reference reaches. Mean density of juvenile steelhead was higher in complex pools compared to non-complex pools throughout the study area. Mean density of juvenile steelhead was higher in pools associated with large wood from washed-out structures compared to pools associated with intact structures in the treatment reach. Changes in smolt production from the treatment reach following the rehabilitation project could not be determined due to trapping difficulties. Only three percent of the smolts emigrating from the basin overwintered in the treatment reach in 1992. Four life history patterns of juvenile steelhead were identified. Only one of the four life history patterns rears in the Meadow Creek basin until smolting. From these findings I conclude that the instream habitat rehabilitation project did not increase the abundance of juvenile steelhead or smolt production during the first two years after treatment. An extended drought and a 20-year flood may have been the dominant factors controlling abundance of juvenile steelhead over the study period. The Meadow Creek rehabilitation project may have limited success at increasing smolt production because it influences only one of four life history patterns of juvenile steelhead during the entire freshwater rearing phase. Close

• 710. [Article] Resource partitioning and reproductive success of three species of hawks (Buteo spp.) in an Oregon prairie

  In a native prairie of Oregon (363 km²) red-tailed (Buteo jamaicensis), ferruginous (Buteo regalis), and Swainson's hawks (Buteo swainsoni) coexist in one of the highest nesting Buteo densities in North ...

  Citation × Citation Citation Abstract Copy Title: Resource partitioning and reproductive success of three species of hawks (Buteo spp.) in an Oregon prairie Author: Cottrell, Marcy Jean In a native prairie of Oregon (363 km²) red-tailed (Buteo jamaicensis), ferruginous (Buteo regalis), and Swainson's hawks (Buteo swainsoni) coexist in one of the highest nesting Buteo densities in North America. In 1979 and 1980, the distribution, density, and productivity of the three species was studied in relation to availability of food and nesting habitat. The degree of ecological segregation among the three species was also investigated. Red-tailed and ferruginous hawks showed considerable overlap in the timing of their nesting cycles; the Swainson's hawk nested about one month later in the spring. The major food item of all three species was the Belding ground squirrel (Spennophilus beldingi). The total dietary overlap among the three hawk species was high: in 1979 and 1980, red-tailed and ferruginous hawks overlapped 90 percent and 80 percent, red-tailed and Swainson's hawks 88 percent and 83 percent, and ferruginous and Swainson's hawks 83 percent and 95 percent. Although timing and use of food resources exhibited considerable overlap, habitat was partitioned. Nine major habitat types occurred within the study area. Red-tailed hawks had almost exclusive use of pine groves and cultivated areas with cottonwood trees. Ferruginous hawks had almost exclusive use of south exposure sites where large rocky outcrops occurred. Use of other habitat types overlapped to some degree. The total habitat overlap between the red-tailed and ferruginous hawk in 1979 and 1980 was 33 percent and 37 percent. The Swainson's hawk exhibited slightly greater overlaps in 1979 and 1980 of 54 percent and 52 percent with red-tailed hawks and 47 percent and 41 percent with ferruginous hawks. Habitat overlap of the Swainson's hawk tended to be minimized by its selection of nest trees whose configuration differed from red-tailed and ferruginous hawks. Space was also partitioned by the maintenance of intraspecific and, to a lesser degree, interspecific nesting territories. Nest success of red-tailed and ferruginous hawks significantly declined when nesting pairs were visible to one another. This suggests that competition for space was a mechanism affecting distribution, density, and nest success. Based on the findings from this study, Buteo management could involve: (1) range management for prey species, which in this case is in accord with good management for cattle, (2) range management for nesting habitat, and (3) maintenance of properly spaced nesting sites. Title: Resource partitioning and reproductive success of three species of hawks (Buteo spp.) in an Oregon prairie Author: Cottrell, Marcy Jean In a native prairie of Oregon (363 km²) red-tailed (Buteo jamaicensis), ferruginous (Buteo regalis), and Swainson's hawks (Buteo swainsoni) coexist in one of the highest nesting Buteo densities in North America. In 1979 and 1980, the distribution, density, and productivity of the three species was studied in relation to availability of food and nesting habitat. The degree of ecological segregation among the three species was also investigated. Red-tailed and ferruginous hawks showed considerable overlap in the timing of their nesting cycles; the Swainson's hawk nested about one month later in the spring. The major food item of all three species was the Belding ground squirrel (Spennophilus beldingi). The total dietary overlap among the three hawk species was high: in 1979 and 1980, red-tailed and ferruginous hawks overlapped 90 percent and 80 percent, red-tailed and Swainson's hawks 88 percent and 83 percent, and ferruginous and Swainson's hawks 83 percent and 95 percent. Although timing and use of food resources exhibited considerable overlap, habitat was partitioned. Nine major habitat types occurred within the study area. Red-tailed hawks had almost exclusive use of pine groves and cultivated areas with cottonwood trees. Ferruginous hawks had almost exclusive use of south exposure sites where large rocky outcrops occurred. Use of other habitat types overlapped to some degree. The total habitat overlap between the red-tailed and ferruginous hawk in 1979 and 1980 was 33 percent and 37 percent. The Swainson's hawk exhibited slightly greater overlaps in 1979 and 1980 of 54 percent and 52 percent with red-tailed hawks and 47 percent and 41 percent with ferruginous hawks. Habitat overlap of the Swainson's hawk tended to be minimized by its selection of nest trees whose configuration differed from red-tailed and ferruginous hawks. Space was also partitioned by the maintenance of intraspecific and, to a lesser degree, interspecific nesting territories. Nest success of red-tailed and ferruginous hawks significantly declined when nesting pairs were visible to one another. This suggests that competition for space was a mechanism affecting distribution, density, and nest success. Based on the findings from this study, Buteo management could involve: (1) range management for prey species, which in this case is in accord with good management for cattle, (2) range management for nesting habitat, and (3) maintenance of properly spaced nesting sites. Close