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Oregon City, OR, United States

Ronan N.A.,Oregon State University | Rosenberg D.K.,Oregon Wildlife Institute
Journal of Wildlife Management | Year: 2014

Studies of habitat relationships indicate that burrowing owls (Athene cunicularia) often select nest sites with multiple burrows. This behavior may increase survival of post-emergent nestlings. We experimentally blocked access to burrows within 20 m of nests (satellite burrows) within a large grassland in central California to evaluate the response by year-round resident burrowing owls to removal of satellite burrows. We compared reproductive performance and nest fidelity between owls whose access to potential satellite burrows was blocked and owls whose nests had similar numbers of naturally occurring burrows within 20 m of the nest prior to manipulation. Adult owls and their young moved away from treatment nests, but reproductive rates between owls from treatment and control nests did not differ. Movements involved the entire family, occurred before young had fledged, and owls did not return to the natal nest burrow. Movements ranged from 25 m to 120 m and occurred at 5 of the 7 treatment nests with young. No such movement occurred at any of the control nests. Our findings support results from correlational studies that multiple nearby burrows influence nest site selection. © 2014 The Wildlife Society © The Wildlife Society, 2014. Source


Hagar J.C.,U.S. Geological Survey | Eskelson B.N.I.,Oregon State University | Haggerty P.K.,U.S. Geological Survey | Nelson S.K.,Oregon State University | Vesely D.G.,Oregon Wildlife Institute
Wildlife Society Bulletin | Year: 2014

LiDAR (Light Detection And Ranging) is an emerging remote-sensing tool that can provide fine-scale data describing vertical complexity of vegetation relevant to species that are responsive to forest structure. We used LiDAR data to estimate occupancy probability for the federally threatened marbled murrelet (Brachyramphus marmoratus) in the Oregon Coast Range of the United States. Our goal was to address the need identified in the Recovery Plan for a more accurate estimate of the availability of nesting habitat by developing occupancy maps based on refined measures of nest-strand structure. We used murrelet occupancy data collected by the Bureau of Land Management Coos Bay District, and canopy metrics calculated from discrete return airborne LiDAR data, to fit a logistic regression model predicting the probability of occupancy. Our final model for stand-level occupancy included distance to coast, and 5 LiDAR-derived variables describing canopy structure. With an area under the curve value (AUC) of 0.74, this model had acceptable discrimination and fair agreement (Cohen's k=0.24), especially considering that all sites in our sample were regarded by managers as potential habitat. The LiDAR model provided better discrimination between occupied and unoccupied sites than did a model using variables derived from Gradient Nearest Neighbor maps that were previously reported as important predictors of murrelet occupancy (AUC=0.64, k=0.12). We also evaluated LiDAR metrics at 11 known murrelet nest sites. Two LiDAR-derived variables accurately discriminated nest sites from random sites (average AUC=0.91). LiDAR provided a means of quantifying 3-dimensional canopy structure with variables that are ecologically relevant to murrelet nesting habitat, and have not been as accurately quantified by other mensuration methods. Published 2014. This article is a U.S. Government work and is in the public domain in the USA. © 2014 The Wildlife Society. Source


Hagar J.,U.S. Geological Survey | Vesely D.,Oregon Wildlife Institute | Haggerty P.,U.S. Geological Survey
GIM International | Year: 2016

The traditional sampling protocol for quantifying potential nesting habitat for murrelet requires an observer to peer up through the tree crown from the forest floor, a task resulting in data of dubious quality. Two-dimensional features of the canopy surface can be quantified using satellite imagery, but the three-dimensional attributes of the inaccessible middle strata of the canopy are the most critical to understanding and mapping the habitat. The development of Lidar as a tool for quantifying forest structure offers great promise of new solutions to existing habitat measurement problems and opens up a ew realm of possibilities for exploring wildlife-habitat relationships. Source


Catlin D.H.,Oregon State University | Rosenberg D.K.,Oregon State University | Rosenberg D.K.,Oregon Wildlife Institute
Journal of Raptor Research | Year: 2014

Natal dispersal is an important driver of population and colonization dynamics, yet factors that affect timing and distance of post-fledging movements are poorly understood. We studied post-fledging movements of 34 (12 male and 22 female) juvenile Burrowing Owls (Athene cunicularia) between June 2002 and April 2003, in a nonmigratory population in the Imperial Valley, California. We found high variation in movement patterns among individuals. Juvenile Burrowing Owls left their nest throughout the year, with two females (6%) remaining within 100 m of their natal burrow until the beginning of the following year's breeding season. Juvenile Burrowing Owls moved up to 11.7 km (males: 397 ± 124 m; females 1762 ± 630 m) between emergence from the nest to the following breeding season. Those that fledged early in the season remained closer to their nests for a longer period than those that fledged later in the season. Female Burrowing Owls remained ≤100 m from their natal nests for a longer duration than males. Members of male-female, but not male-male, sibling pairs were more likely to be within 100 m of one another than members of female-female sibling pairs. After members of sibling pairs were >100 m apart, distance between members of sibling pairs was related only to time since fledging. Our study, conducted in a highly simplified agricultural environment, provides evidence that sex, fledging date, and sibling relationships can be responsible for the high individual variation in post-fledging movements of Burrowing Owls that has often been attributed to environmental variation. © 2014 The Raptor Research Foundation, Inc. Source


Haley K.L.,Oregon State University | Haley K.L.,Florida Fish And Wildlife Conservation Commission | Rosenberg D.K.,Oregon State University | Rosenberg D.K.,Oregon Wildlife Institute
Journal of Raptor Research | Year: 2013

Reproductive strategies of birds are shaped by patterns of food supply, yet empirical evidence of the consequences and mechanisms of food limitation on reproductive performance is inconsistent, probably due to variable responses from species of differing life-history strategies. We tested the hypothesis that food supplementation would increase reproductive rates of a nonmigratory population of Burrowing Owls (Athene cunicularia) via direct and indirect pathways. We predicted increasing food availability would directly increase growth and survival of the youngest nestlings and would indirectly decrease predation rates of eggs and nestlings by increasing nest attendance. We experimentally supplemented food from clutch completion through brood-rearing during two breeding seasons (April-July 1999 and 2000) in the agricultural matrix of the Imperial Valley, in southeastern California. In both years, hatching success (hatchlings/egg laid) was similar between supplemented and non-supplemented nests, but the proportion that survived to 28 d was higher in food-supplemented nests. Growth rates and survival rates of last-hatched young were lower in non-supplemented than supplemented nests in only one year of the study. A greater proportion of hatchling deaths were attributed to starvation in non-supplemented nests. Nest attendance was greater in supplemented nests although low predation for supplemented and non-supplemented nests resulted in no effects on reproductive success. Our results were consistent with the brood-reduction hypothesis that predicts that food supplementation would result in a greater number of fledglings by increasing survival of the youngest nestlings through increased growth rates when hatching asynchrony exists and food is limited. © 2013 The Raptor Research Foundation, Inc. Source

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