Nesting habitat of Mexican spotted owls in the Sacramento Mountains, New Mexico (original) (raw)

Evaluating Desired Conditions for Mexican Spotted Owl Nesting and Roosting Habitat

Forest Science, 2016

The Mexican spotted owl (Strix occidentalis lucida) was listed as a threatened species in 1993, primarily because of concerns over the loss of late seral forest habitat to timber harvest and wildfire. A recovery plan prepared for this owl subspecies explicitly assumed that nesting (and/or roosting) habitat was a primary factor limiting distribution of Mexican spotted owls and provided four desired conditions for identifying and managing potential owl nesting/roosting habitat in forested habitat. We used data collected at nest sites of Mexican spotted owls in the Sacramento Mountains, New Mexico, to evaluate how well these desired conditions and associated forest structural attributes described nesting habitat in this area. All nest sites included in our analyses successfully fledged young during the study. These nest sites generally featured higher levels of the structural attributes included in the desired conditions (total basal area, density of trees Ͼ46 cm in dbh, percentage of basal area in trees 30-46 cm dbh, and percentage of basal area in trees Ͼ46 cm dbh) than the surrounding stand, yet only 46-87% of sampled nest sites met single desired conditions and only 22% met all four conditions simultaneously. The best generalized linear models using combinations of these four structural attributes plus canopy cover to distinguish between nest sites and random sites within owl home ranges all contained canopy cover and percentage of basal area in trees Ͼ46 cm dbh. Relative importance values were high for both of these attributes (1.000 and 0.983, respectively), and confidence intervals around parameter estimates included zero for all other attributes. The present combination of four desired conditions did not consistently identify nesting habitat in this area, required managing for levels of structural attributes that were greater than levels typically observed at successful owl nest sites, and did not include canopy cover, which was the single best predictor in the Sacramento Mountains. We recommend revising the desired conditions in the Sacramento Mountains to emphasize canopy cover and some attribute measuring the large tree component. We also recommend repeating this assessment in other geographic areas to determine how well the desired conditions for those areas describe nesting habitat for owls.

Old-forest distribution around spotted owl nests in central cascade mountains

1999

Unlike previous spotted owl (Strix occidentalis) habitat association studies, we restricted our inquiry to the old-forest type and thus explored the association of spotted owls with habitat distribution as opposed to habitat type. We compared old-forest distribution around 126 northern spotted owl (S. o. caurina) nests in 70 pair territories, 14 nonreproductive spotted owl activity centers, and 104 points drawn randomly from old forest (closed canopy, >80 yr) in the central Cascade Mountains of Oregon. We quantified the percentage of old forest within 50 concentric circular plots (0.1-5.0-km radii) centered on each analyzed point, and we used logistic regression to make spatially explicit inferences. Owl nests were surrounded by more old forest in plots with 0.2-0.8-km radii (P < 0.05). Results suggested the landscape scales most pertinent to northern spotted owl nest-site positioning in this study were (in descending order) (1) the surrounding 15 ha (approx 200-m radius), (2) the surrounding 30-115 ha (approx 300-600-m radius), (3) the surrounding 200 ha (800-m radius), and (4) possibly the surrounding 700 ha (1,500-m radius). Nests were associated with higher proportions of old forest near the nest, implying that the arrangement of habitat was important for nest-site selection, positioning, or both. The 70 territories of nesting owls had more old forest on average than did the 14 nonreprodu•tive owl sites, and the probability that a pair nested at least once during the study was positively associated with area of old-forest habitat in all radii studied. Because spotted owls in the central Cascade Mountains of Oregon are known to have home ranges that average 1,769 ha, our results apply to nest-site location on the landscape and not to the amount of habitat necessary for pair persistence or successful reproduction.

Canopy Closure around Nest Sites of Mexican Spotted Owls in Northcentral Arizona

The Journal of Wildlife Management, 1997

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. . Wiley and Wildlife Society are collaborating with JSTOR to digitize, preserve and extend access to The Journal of Wildlife Management. Abstract: We analyzed variation in canopy closure around 47 Mexican spotted owl (Strix occidentalis lucida) nest sites 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 (<10, 10-40, 41-70, or >70%), and measured the area in each canopy class within 5 concentric analysis zones with radii of . Landscape composition differed between spotted owl nest and random sites (P < 0.001). Differences were greatest within 0.4 km of nest and random sites but persisted across all analyses zones. Nest sites contained more area in the >70% canopy-closure class and less area in the < 10% class. The most abundant canopy class was 41-70%, except within 0.1 km of nests, where >70% canopy predominated. Nesting spotted owls selected areas with denser canopy than randomly available forest landscapes, but outside the immediate nest area (>0.8 km) canopy closure approached that of the surrounding forest.

Old-Forest Distribution around Spotted Owl Nests in the Central Cascade Mountains, Oregon

Journal of Wildlife Management, 1999

Cover of tall trees best predicts California spotted owl habitat

Forest Ecology and Management, 2017

Restoration of western dry forests in the USA often focuses on reducing fuel loads. In the range of the spotted owl, these treatments may reduce canopy cover and tree density, which could reduce preferred habitat conditions for the owl and other sensitive species. In particular, high canopy cover (≥70%) has been widely reported to be an important feature of spotted owl habitat, but averages of stand-level forest cover do not provide important information on foliage height and gap structure. To provide better quantification of canopy structure, we used airborne LiDAR imagery to identify canopy cover in different height strata and the size and frequency of gaps that were associated with owl nest sites, protected activity centers (PACs), and territories within four study areas and 316 owl territories. Although total canopy cover was high in nest stands and PAC areas, the cover in tall (> 48 m) trees was the canopy structure most highly selected for, while cover in lower strata (2-16 m) was avoided compared to availability in the surrounding landscape. Tall tree cover gradually decreased and lower strata cover increased as distance increased from the nest. Large (> 1000 m 2) gaps were not found near nests, but otherwise there was no difference in gap frequencies and sizes between PACs and territories and the surrounding landscape. Using cluster analysis we classified canopy conditions into 5 structural classes and 4 levels of canopy cover to assess the relationship between total canopy cover and tree size within nest sites, PACs, and territories. High canopy cover (≥70%) mostly occurs when large tree cover is high, indicating the two variables are often confounded. Our results suggest that the cover of tall trees may be a better predictor of owl habitat than total canopy cover because the latter can include cover in the 2-16 m strataconditions that owls actually avoid. Management strategies designed to preserve and facilitate the growth of tall trees while reducing the cover and density of understory trees may improve forest resilience to drought and wildfire while also maintaining or promoting the characteristics of owl habitat.

Site occupancy, apparent survival, and reproduction of California spotted owls in relation to forest stand characteristics

The Journal of wildlife …, 2005

The California spotted owl (Strix occidentalis occidentalis) has been at the center of political and administrative debate due to its association with commercially valuable forest. Several studies have compared the forest cover types used by California spotted owls with the cover types that are generally available, establishing the association between spotted owls and old/large tree components of forests at the landscape scale. We sought a deeper understanding of spotted owl habitat associations in areas in which owls had already selected territories. We mapped and classified vegetation within circular plots (radius 2.4 km) around 67 spotted owl sites in northeastern California, USA. We evaluated the relationships between habitat composition within the different owl sites and variation in (1) nest success (1990-2000) and (2) site occupancy, apparent survival probability, and reproductive output (1993-1998). All analyses included data representing 2 spatial scales: core area (814 ha) and nest area (203 ha). Site occupancy was positively associated with the amount of the nest area dominated by large trees with high canopy cover within the nest area. It was negatively associated with the amount of nonhabitat (nonforested areas and forest cover types not used for nesting or foraging) and with medium-sized trees with high canopy cover. Site occupancy also decreased with time and elevation. Apparent survival probability varied annually and was positively related to the area of each habitat class multiplied by the quotient proportion used/proportion available for each type, at both the nest and core scales. Reproductive output was negatively related to elevation and nonhabitat within the nest area. Nest success was positively associated with the presence of large remnant trees within the nest stand.

Landscape composition around northern spotted owl nests, central Cascade Mountains, Oregon

1997

I have often wondered what this nation would look like without the efforts of those whom have cared about and for its natural heritage. Having had the honor and pleasure to know and work with the following individuals and organizations I now know what the nation would look like without their stewardship and citizenship. All too often those of us concerned about our cultural heritage forget that it is inextricable from our natural heritage. I know that the following people and organizations have served the people of this nation for years to come through their love for and dedication to our natural resources and their stewardship. In their regard, I put forward this document, knowing that it cannot serve justice to their efforts that are, however, realized on the landscape. I do hope that this study will provide some further assistance to understanding the northern spotted owl; a fascinating and remarkable component of the world we belong to that would be inexcusable and unforgivable to lose. This study was made possible by and greatly benefitted from over 25 years of work and research on the northern spotted owl conducted by the Oregon Cooperative Wildlife Research Unit under the original leadership of Dr. Howard M. Wight, then Dr. E. Charles Meslow and now by Dr. Robert G. Anthony. Under the auspices of the Unit, Dr. Eric D. Forsman began studying the owl in the early 1970's in the vicinity of the H.J. Andrews Experimental Forest. Dr. Forsman's initial investigations were of the owls' life-history and habits, home-range size and composition, and habitat use. In the early 1980's Gary S. Miller studied juvenile owl dispersal and survival and then began the density and demography study that still continues today under Jim Thrailkill's leadership. Many of the owl territories and owls that Eric and Gary originally identified were part of this study and I am indebted to them. Funding for these studies was provided through several grants by the U. S.

Projected trends in owl habitat

1992

Here we attempt to synthesize many of the analyses presented in other chapters in this document, and to look ahead to the future. As such, this chapter is necessarily more speculative and conclusions expressed here should not be viewed as hard and prescriptive. We hope, however, to highlight areas of concern for future owl habitat, and for the health of the forest ecosystem more generally. Finally, we propose alternate forest management methods that we believe have merit. We do not consider the management methods described here to be an exclusive set to be prescribed forestwide. Rather we view them as potential experiments which, if effective, will alleviate many of the shortcomings that we perceive in current management systems as they relate to owl habitat. This report covers a wide range of forest types and topographic regions. We will focus almost exclusively on the Sierran mixed-conifer forest type, as it contains an estimated 82 percent of the spotted owl sites in the Sierra Nevada and 62 percent of all known California spotted owl sites.

Mexican spotted owl home range and habitat use in pine-oak forest: implications for forest management

To better understand the habitat relationships of the Mexican spotted owl (Strix occidentalis lucida), and how such relationships might influence forest management, we studied home-range and habitat use of radio-marked owls in ponderosa pine (Pinus ponderosa)-Gambel oak (Quercus gambeli~) forest. Annual home-range size (95% adaptive-kernel estimate) averaged 895 ha * 70 (SE) for 1 2 individuals and 997 ha + 186 (SE) for 7 pairs of owls. On average, the 75% adaptive-kernel contour (a probability contour containing 75% of the owl locations) included 32 and 30% of the annual home range for individuals and pairs, respectively, suggesting high concentration of activity in a relatively small portion ofthe home range. Relative area of three covertypes (ponderosa pine forest, pineaak forest, and meadow) did not differ between seasonal ranges, and owls used these covertypes in proportion to their relative area during both breeding and nonbreeding seasons. In contrast, relative area of four c...

Range-wide analysis of northern spotted owl nesting habitat relations

Forest Ecology and Management, 2015

Recently the US Fish and Wildlife Service, as part of a critical habitat analysis for the northern spotted owl (Strix occidentalis caurina), developed habitat suitability models based on thousands of owl nest sites distributed across 11 regions using the MaxEnt tool. Because these models formed the basis for critical habitat designations on millions of hectares of land, we undertook an independent evaluation of the FWS effort. We evaluated the accuracy of vegetation data used as input to develop the models, conducted out of sample analyses, correlated model output with owl reproductive success in two study areas, and developed alternate models using two different statistical methods. Vegetation data appeared accurate for only a few variables, and accuracy varied among model regions. Out of sample testing gave a high rate of classification errors and owl productivity was not correlated with MaxEnt model output in two study areas. Alternate statistical methods produced reasonable models with fewer variables. Critically, neither the models compared across regions nor the regions analyzed with different tools led to comparable use of variables. Thus biological interpretation of owl habitat selection models seemed ambiguous. In addition, for MaxEnt and one of the other tools, a highly significant trend by regression was found showing decreasing model accuracy as number of training nest sites increased. Together, these two results suggest that the generated models may be spurious to some unknown degree, perhaps because the underlying vegetation data, also derived from a model, are not sufficiently accurate to support the analysis and/or because the owls themselves affect habitat suitability by consuming their prey base. We suggest that the USFWS exercise caution in using MaxEnt models as a basis for regulatory purposes such as consultation, estimating likelihood of occupancy by owls, or evaluation of site-specific recovery actions.

Nesting habitat of Mexican spotted owls in the Sacramento Mountains, New Mexico (original) (raw)

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