Download or read book Geographic Distributions of Prey of the Northern Spotted Owl in the Central Western Cascades Oregon 1988 2009 written by Alexis Smoluk and published by . This book was released on 2011 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spatial variation in the diet of the northern spotted owl (Strix occidentalis caurina) influences owl home ranges, and understanding this relationship will aid managers in forest management prescriptions that influence spotted owl recovery. This study describes the spatial variation in owl diet based on 4183 prey collected at 114 owl territories in 1833 km2 area of the Central West Cascades during 1988-2009. The study addressed two questions: (1) What are the spatial patterns of owl territories and prey in owl pellets? (2) What landscape characteristics explain the composition of spotted owl prey? Thirteen prey species/groups were identified as key prey to spotted owl diets because they appeared in 10% of owl territories, comprised 90% of the total abundance and 95% of the total biomass across all pellet samples. Northern flying squirrels (Glaucomys sabrinus) were the most important prey in all areas, comprising 46-64% of prey abundance and 48-75% of prey biomass. The spatial distribution of key prey species, especially red tree voles (Arborimus longicaudus), pocket gophers (Thomomys mazama), and rabbits/hares (Sylvilagus bachmani /Lepus americanus) was significantly related to easting, elevation, and fine-scale relief. Red tree voles were more abundant in owl diets at low elevation, with high fine-scale relief and in the western portions of the study area, whereas pocket gophers and rabbits/hares were more abundant in owl diets at high elevation, with low fine-scale relief and in the eastern portions of the study area. Owl territories exhibited a significantly dispersed spatial pattern in almost all years, but the mean nearest neighbor distance between owl territories was 2090m in the western and 3000m in the eastern portions of the study area. Differences in owl pair densities and nearest neighbor distances were related to spatial patterns in owl diet. Where red tree voles comprised a higher proportion of the diet, owl pair density was higher and owl territories were more closely packed than where pocket gophers predominated. These findings suggest that (1) differences in diet among local areas was due to differences in key prey availability, which in turn are influenced by vegetation zone and topography, (2) at high elevation spotted owl sites with abundant pocket gophers and few woodrats in the diet, owl dietary dependence on flying squirrels over the winter and early in the nesting period may require owls to occupy larger territories than owls require in lower elevations, and (3) the spatial variation in owl diets and associated variation in owl pair densities and nearest neighbor distances suggest that owl habitat requirements vary within the West Cascades physiographic province, raising questions about the use of one-size-fits-all habitat values as a management strategy. These findings may be relevant for regulatory agencies and forest managers as they work to recover the spotted owl.
Download or read book Final Environmental Impact Statement on Management for the Northern Spotted Owl in the National Forests written by and published by . This book was released on 1992 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Northwest Forest Plan the First 10 Years 1994 2003 written by Joseph Lint and published by . This book was released on 2005 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Final Environmental Impact Statement on Management for the Northern Spotted Owl in the National Forests written by United States. Forest Service and published by . This book was released on 1992 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Habitat Utilization by Spotted Owls in the West Central Cascades of Oregon written by Eric D. Forsman and published by . This book was released on 1980 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Eight adult spotted owls (Strix occidentalis) on the west slope of the Cascade Range in Oregon were fitted with radio transmitters and observed for periods ranging from 271 to 383 days. Mean home range size for the owls was 1,177 ha (range = 920-1,376 ha). There was no significant difference between home range size of males and females. On the average, home ranges of individuals occupying adjacent territories overlapped by 12 percent (range = 3-25 percent). Home ranges of paired individuals overlapped by 50 to 73 percent. The size and shape of home ranges varied on a seasonal basis; generally, the largest home ranges were observed during winter. Nest sites were centrally located within the home ranges utilized by the owls. On the radiotelemetry study area, the mean nearest neighbor distance between nests of adjacent pairs was 2.88 km. On 11 other areas in western Oregon where suitable habitat was available, mean nearest neighbor distances ranged from 1.68 to 3.04 km. The overall mean nearest neighbor distance for the 12 areas was 2.42 km. Home ranges occupied by the radio tagged owls were so large that consistent defense of the entire home range was impossible. Territorial defense appeared to take the form of a decreasing zone of influence centered around the nest; areas near each nest were defended consistently, but defense became increasingly inconsistent with distance from the nest. Discrete territorial boundaries could not be determined and probably did not exist. Territorial interactions between individuals of the same sex were much more aggressive than interactions between individuals of opposite sex. Spotted owls may have responded less aggressively toward individuals of the opposite sex because the advantage of allowing potential mate replacements to remain within the territory outweighed other considerations. Except for a few instances in which 2 of the owls foraged in recently clear-cut areas or in rock talus, virtually all foraging occurred in forests over 30 years old. Old-growth forests, which covered 36 to 64 percent of the area on individual owl home ranges, were strongly preferred for foraging by all of the owls; 92 percent of all foraging occurred in such forests. Utilization of younger forests (30 to 200 years old) was generally either less than or not significantly different than expected, indicating that younger forests were less desirable for foraging than old-growth stands. Old-growth forests were also preferred for roosting (97 percent of all roosts). Large old trees apparently were preferred for roosting during inclement weather because they provided better overhead protection from rain and snow. Small trees in the understory were preferred during warm weather because they provided greater protection from high temperatures and solar radiation. Spotted owls were primarily nocturnal. On the average, they left their day roasts to begin foraging at 14 minutes after sunset and stopped foraging at 21 minutes before sunrise. Diurnal foraging was limited primarily to opportunistic attempts to capture animals that wandered into roost areas. The usual method of foraging was to move from perch to perch at night, watching and listening for potential prey. The average rate of movement while foraging in this manner was 247 m/hr, and the average distance moved per nightly foraging period was 2,782 meters (range = 320-8,895 m). Seven species of mammals comprised the nucleus of the diet, the northern flying squirrel (Glaucomys sabrinus), red tree vole (Phenacomys longicaudus), western red-backed vole (Clethrionomys occidentalis), deer mouse (Peromyscus maniculatus), western pocket gopher (Thomomys mazama), snowshoe hare (Lepus americanus), and bushy-tailed woodrat (Neotoma cinerea). The flying squirrel, the most common animal in the diet, comprised 42 percent of all prey captured. During mid-winter, 85 percent of the prey captured were arboreal mammals. During the rest of the year, terrestrial prey became more abundant in the diet, but the flying squirrel remained the most common animal in the diet. Mean prey size and dietary composition for male and female spotted owls were not significantly different; this suggested that males and females did not partition the prey resource on the basis of size or species. Estimates of biomass consumed per owl per day on the study area ranged from 77.6 to 164.8 g, but the latter estimate was probably inflated. Four hypotheses are presented to explain why spotted owls foraged primarily in older forests and avoided recently cutover areas: (1) the biomass of prey preferred by the owls may have been greater in older forests than in cutover areas, (2) switching from arboreal mammals in older forests to terrestrial mammals in cutover areas might have resulted in increased competition with other nocturnal predators, (3) prey may have been less accessible in the dense vegetation that developed on cutover areas, and (4) spotted owls may have been more susceptible to predation in cutover areas where escape cover was absent.
Download or read book Of Spotted Owls Old Growth and New Policies written by Bruce G. Marcot and published by . This book was released on 1997 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recovery Plan for the Northern Spotted Owl Draft written by and published by . This book was released on 1991 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Competitive Interactions and Resource Partitioning Between Northern Spotted Owls and Barred Owls in Western Oregon written by J. David Wiens and published by . This book was released on 2012 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: The federally threatened northern spotted owl (Strix occidentalis caurina) is the focus of intensive conservation efforts that have led to much forested land being reserved as habitat for the owl and associated wildlife species throughout the Pacific Northwest of the United States. Recently, however, a relatively new threat to spotted owls has emerged in the form of an invasive competitor: the congeneric barred owl (Strix varia). As barred owls have rapidly expanded their populations into the entire range of the northern spotted owl, mounting evidence indicates that they are displacing, hybridizing with, and even killing spotted owls. The barred owl invasion into western North America has made an already complex conservation issue even more contentious, and a lack of information on the ecological relationships between the 2 species has hampered conservation efforts. During 2007-2009 I investigated spatial relationships, habitat selection, diets, survival, and reproduction of sympatric spotted owls and barred owls in western Oregon, USA. My overall objective was to determine the potential for and possible consequences of competition for space, habitat, and food between the 2 species. My study included 29 spotted owls and 28 barred owls that were radio-marked in 36 neighboring territories and monitored over a 24-month tracking period. Based on repeated surveys of both species, the number of territories occupied by pairs of barred owls in the 745 km2 study area (82) greatly outnumbered those occupied by pairs of spotted owls (15). Estimates of mean size of home-ranges and core-use areas of spotted owls (1,843 ha and 305 ha, respectively) were 2-4 times larger than those of barred owls (581 ha and 188 ha, respectively). Individual spotted and barred owls in adjacent territories often had overlapping home ranges, but inter-specific space sharing was largely restricted to broader foraging areas in the home range with minimal spatial overlap among core-use areas. I used an information-theoretic approach to rank discrete choice models representing alternative hypotheses about the influence of forest conditions and interspecific interactions on species-specific patterns of nighttime habitat selection. Spotted owls spent a disproportionate amount of time foraging on steep slopes in ravines dominated by old (>120 yrs old) conifer trees. Barred owls used available forest types more evenly than spotted owls, and were most strongly associated with patches of large hardwood and conifer trees that occupied relatively flat areas along streams. Spotted and barred owls differed in the relative use of old conifer forest (higher for spotted owls) and slope conditions (steeper slopes for spotted owls). I found no evidence that the 2 species differed in their use of young, mature, and riparian-hardwood forest types, and both species avoided forest-nonforest edges. The best resource selection function for spotted owls indicated that the relative probability of a location being selected was reduced if the location was within or in close proximity to a core-use area of a barred owl. I used pellet analysis and measures of food niche overlap to examine the potential for dietary competition between spatially associated pairs of spotted owls and barred owls. I identified 1,223 prey items from 15 territories occupied by pairs of spotted owls and 4,299 prey items from 24 territories occupied by pairs of barred owls. Diets of both species were dominated by nocturnal mammals, but diets of barred owls included many terrestrial, aquatic, and diurnal prey species that were rare or absent in diets of spotted owls. Northern flying squirrels (Glaucomys sabrinus), woodrats (Neotoma fuscipes, N. cinerea), and lagomorphs (Lepus americanus, Sylvilagus bachmani) were particularly important prey for both owl species, accounting for 81% and 49% of total dietary biomass for spotted owls and barred owls, respectively. Dietary overlap between pairs of spotted and barred owls in adjacent territories ranged from 28-70% (mean = 42%) In addition to overlap in resource use, I also identified strong associations between the presence of barred owls and the behavior of spotted owls, as shown by changes in space-use, habitat selection, and reproductive output of spotted owls exposed to different levels of spatial overlap with barred owls in adjacent territories. Barred owls in my study area displayed both numeric and demographic superiority over spotted owls; the annual survival probability of radio-marked spotted owls from known-fate analyses (0.81, SE = 0.05) was lower than that of barred owls (0.92, SE = 0.04), and barred owls produced over 6 times as many young over a 3-year period as spotted owls. Survival of both species was positively associated with an increasing proportion of old (>120 yrs old) conifer forest within the home range, which suggested that availability of old forest was a potential limiting factor in the competitive relationship between the 2 species. When viewed collectively, my results support the hypothesis that interference competition with a high density of barred owls for territorial space can act to constrain the availability of critical resources required for successful recruitment and reproduction of spotted owls. My findings have broad implications for the conservation of spotted owls, as they suggest that spatial heterogeneity in survival and reproduction may arise not only because of differences among territories in the quality of forest habitat, but also because of the spatial distribution of an invasive competitor.
Download or read book Distribution and Biology of the Spotted Owl in Oregon written by Eric D. Forsman and published by . This book was released on 1984 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Influence of Habitat Abundance and Fragmentation on Northern Spotted Owls in Western Oregon written by Joseph S. Meyer and published by . This book was released on 1998 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Current management for the northern spotted owl (Strix occidentalis caurina) is largely driven by metapopulation models or individually-based models that assume the success of juvenile dispersal in a fragmented landscape is a primary factor determining the future existence of spotted owls in the Pacific Northwest. We tested hypotheses about fragmentation by comparing sites known to be occupied by spotted owls with random sites to determine if relationships existed between landscape indices and spotted owl presence and productivity in western Oregon"--Page 5
Download or read book The Northern Spotted Owl and the Endangered Species Act written by United States. Congress. House. Committee on Merchant Marine and Fisheries. Subcommittee on Fisheries and Wildlife Conservation and the Environment and published by . This book was released on 1990 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Contribution of Federal and Non federal Habitat to Persistence of the Northern Spotted Owl on the Olympic Peninsula Washington written by and published by . This book was released on 1995 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Northern Spotted Owl written by and published by . This book was released on 1997 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Northern Spotted Owl Effectiveness Monitoring Plan for the Northwest Forest Plan written by Joseph Lint and published by . This book was released on 1999 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ecology of the Spotted Owl in Oregon and Washington written by and published by . This book was released on 1986 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Competitive Interactions and Resource Partitioning Between Northern Spotted Owls and Barred Owls in Western Oregon written by J. David Wiens and published by . This book was released on 2012 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: The federally threatened northern spotted owl (Strix occidentalis caurina) is the focus of intensive conservation efforts that have led to much forested land being reserved as habitat for the owl and associated wildlife species throughout the Pacific Northwest of the United States. Recently, however, a relatively new threat to spotted owls has emerged in the form of an invasive competitor: the congeneric barred owl (Strix varia). As barred owls have rapidly expanded their populations into the entire range of the northern spotted owl, mounting evidence indicates that they are displacing, hybridizing with, and even killing spotted owls. The barred owl invasion into western North America has made an already complex conservation issue even more contentious, and a lack of information on the ecological relationships between the 2 species has hampered conservation efforts. During 2007-2009 I investigated spatial relationships, habitat selection, diets, survival, and reproduction of sympatric spotted owls and barred owls in western Oregon, USA. My overall objective was to determine the potential for and possible consequences of competition for space, habitat, and food between the 2 species. My study included 29 spotted owls and 28 barred owls that were radio-marked in 36 neighboring territories and monitored over a 24-month tracking period. Based on repeated surveys of both species, the number of territories occupied by pairs of barred owls in the 745 km2 study area (82) greatly outnumbered those occupied by pairs of spotted owls (15). Estimates of mean size of home-ranges and core-use areas of spotted owls (1,843 ha and 305 ha, respectively) were 2-4 times larger than those of barred owls (581 ha and 188 ha, respectively). Individual spotted and barred owls in adjacent territories often had overlapping home ranges, but inter-specific space sharing was largely restricted to broader foraging areas in the home range with minimal spatial overlap among core-use areas. I used an information-theoretic approach to rank discrete choice models representing alternative hypotheses about the influence of forest conditions and interspecific interactions on species-specific patterns of nighttime habitat selection. Spotted owls spent a disproportionate amount of time foraging on steep slopes in ravines dominated by old (>120 yrs old) conifer trees. Barred owls used available forest types more evenly than spotted owls, and were most strongly associated with patches of large hardwood and conifer trees that occupied relatively flat areas along streams. Spotted and barred owls differed in the relative use of old conifer forest (higher for spotted owls) and slope conditions (steeper slopes for spotted owls). I found no evidence that the 2 species differed in their use of young, mature, and riparian-hardwood forest types, and both species avoided forest-nonforest edges. The best resource selection function for spotted owls indicated that the relative probability of a location being selected was reduced if the location was within or in close proximity to a core-use area of a barred owl. I used pellet analysis and measures of food niche overlap to examine the potential for dietary competition between spatially associated pairs of spotted owls and barred owls. I identified 1,223 prey items from 15 territories occupied by pairs of spotted owls and 4,299 prey items from 24 territories occupied by pairs of barred owls. Diets of both species were dominated by nocturnal mammals, but diets of barred owls included many terrestrial, aquatic, and diurnal prey species that were rare or absent in diets of spotted owls. Northern flying squirrels (Glaucomys sabrinus), woodrats (Neotoma fuscipes, N. cinerea), and lagomorphs (Lepus americanus, Sylvilagus bachmani) were particularly important prey for both owl species, accounting for 81% and 49% of total dietary biomass for spotted owls and barred owls, respectively. Dietary overlap between pairs of spotted and barred owls in adjacent territories ranged from 28-70% (mean = 42%) In addition to overlap in resource use, I also identified strong associations between the presence of barred owls and the behavior of spotted owls, as shown by changes in space-use, habitat selection, and reproductive output of spotted owls exposed to different levels of spatial overlap with barred owls in adjacent territories. Barred owls in my study area displayed both numeric and demographic superiority over spotted owls; the annual survival probability of radio-marked spotted owls from known-fate analyses (0.81, SE = 0.05) was lower than that of barred owls (0.92, SE = 0.04), and barred owls produced over 6 times as many young over a 3-year period as spotted owls. Survival of both species was positively associated with an increasing proportion of old (>120 yrs old) conifer forest within the home range, which suggested that availability of old forest was a potential limiting factor in the competitive relationship between the 2 species. When viewed collectively, my results support the hypothesis that interference competition with a high density of barred owls for territorial space can act to constrain the availability of critical resources required for successful recruitment and reproduction of spotted owls. My findings have broad implications for the conservation of spotted owls, as they suggest that spatial heterogeneity in survival and reproduction may arise not only because of differences among territories in the quality of forest habitat, but also because of the spatial distribution of an invasive competitor.
Download or read book A Conservation Strategy for the Northern Spotted Owl written by and published by . This book was released on 1990 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt:
