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We studied Mexican spotted owl (Strix occidentalis lucida) diets and the relative abundance and habitat associations of major prey species in a ponderosa pine (Pinus ponderosa)-Gambel oak (Quercus gambelii) forest in north-central Arizona, USA, from 1990 to 1993. The owl's diet was comprised of 94% mammals by biomass and consisted of primarily the deer mouse (Peromyscus maniculatus), brush mouse (P boylii), Mexican woodrat (Neotoma mexicana), and Mexican vole (Microtus mexicanus). Spotted owl prey in our study area were smaller on average than prey in other locations, and the total biomass of potential prey was less than that reported in other areas within the owl's geographic range. Although all prey populations...
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We analyzed variation in canopy closure around 47 Mexican spotted owl (Strix occidentalis lucida) nest sires and 47 random forest sites on the Coconino National Forest in northcentral Arizona. We mapped distinct habitat polygons on 1:15,840 color aerial photographs, assigned each polygon to one of 4 canopy-closure classes (70%), and measured the area in each canopy class within 5 concentric analysis zones with radii of 0.1, 0.4, 0.8, 1.2, and 1.6 km (delineating rings of about 4, 47, 150, 252, and 352 ha). Landscape composition differed between spotted owl nest and random sites (P 70% canopy-closure class and less area in the 70% canopy predominated Nesting spotted owls selected areas with denser canopy than randomly...
We studied first-year movements of Mexican Spotted Owls (Strix occidentalis lucida) during natal dispersal in canyonlands of southern Utah. Thirty-one juvenile Mexican Spotted Owls were captured and radiotracked during 1992-95 to examine behavior and conduct experiments related to the onset of natal dispersal. Juvenile Spotted Owls dispersed from their nest areas during September to October each year, with 85% leaving in September. The onset of movements was sudden and juveniles dispersed in varied directions. The median distance from nest area to last observed location was 25.7 km (range = 1.7-92.3 km). Three of 26 juveniles tracked (11%) were alive after one year, although none were observed with mates. We conducted...
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This dataset contains the result of the bioclimatic-envelope modeling of nine bird species -- Northern/Masked Bobwhite Quail (Colinus virginianus), Scaled Quail (Callipepla squamata), Pinyon Jay (Gymnorhinus cyanocephalus), Juniper Titmouse (Baeolophus ridgwayi), Mexican Spotted Owl (Strix occidentalis lucida), Cassin’s Sparrow (Peucaea cassinii), Lesser Prairie-Chicken (Tympanuchus pallidicinctus), Montezuma Quail (Cyrtonyx montezumae), and White-tailed Ptarmigan (Lagopus leucurus) -- in the South Central US using the downscaled data provided by WorldClim. We used five species distribution models (SDM) including Generalized Linear Model, Random Forest, Boosted Regression Tree, Maxent, and Multivariate Adaptive...
The recovery plan for the Mexican spotted owl (Strix occidentalis lucida) recommended protection of owl nesting and roosting habitat. Descriptions of rnicrohabitat (less than or equal to-0.04 ha) characteristics associated with suitable nesting sites have been limited for the area of pine-oak forest occupied by this species in Arizona, USA. Therefore, we studied Mexican spotted owl habitat on a 585-km(2) study area on the Coconino Plateau near Flagstaff, Arizona. Mexican spotted owls nested primarily in mature (greater than or equal to45.7-cm diameter at breast height dbh) Gambel oak (Quercus gambelii; 40%) and ponderosa pine (Pines ponderosa; 37%) trees. We examined a plausible set of a priori models using both...
The Mexican spotted owl (Strix occidentalis lucida) is a threatened subspecies whose recovery depends, in part, on both an understanding of its habitat requirements and the protection of its habitat. Therefore, we evaluated habitat composition and configuration around owl sites in the Tularosa Mountains, New Mexico, using a vegetation map derived from Landsat Thematic Mapper (TM) digital imagery and digital elevation models. Owls occupied sites with more mature mixed-conifer and mature pine and less pinyon-juniper than random sites. No difference existed in the amount of young forest between owl and random sites. After correcting for the area of the vegetation classes within owl territories, no difference existed...
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Finite population sampling theory is useful in estimating total population size (abundance) from abundance estimates of each sampled unit (quadrat). We develop estimators that allow correlated quadrat abundance estimates, even for quadrats in different sampling strata. Correlated quadrat abundance estimates based on mark-recapture or distance sampling methods occur when data are pooled across quadrats to estimate, for example, capture probability parameters or sighting functions. When only minimal information is available from each quadrat, pooling of data across quadrats may be necessary to efficiently estimate capture probabilities or sighting functions. We further include information from a quadrat-based auxiliary...


map background search result map search result map Estimating population size with correlated sampling unit estimates Canopy closure around nest sites of Mexican spotted owls in northcentral Arizona Projected future bioclimate-envelope suitability for bird species in South Central USA Canopy closure around nest sites of Mexican spotted owls in northcentral Arizona Estimating population size with correlated sampling unit estimates Projected future bioclimate-envelope suitability for bird species in South Central USA