Great gray owls ( Strix nebulosa ) in Yosemite National Park: on the importance of food, forest structure, and human disturbance

Charles van Riper; Joseph J. Fontaine; Jan W. van Wagtendonk

doi:10.3375/043.033.0307

Home/Archive/USGS

USGS · 70047851

Great gray owls ( Strix nebulosa ) in Yosemite National Park: on the importance of food, forest structure, and human disturbance

Charles van Riper·Joseph J. Fontaine·Jan W. van Wagtendonk

View original source ↗Export metadata ↓

Abstract

We studied great gray owls (Strix nebulosa Forster) in Yosemite National Park, California, measuring variables that could potentially influence patterns of occurrence and conservation of this stateendangered species. We found that owl presence was closely tied to habitat (red fir (Abies magnified A. Murray) and the abundance of meadows), prey, and snags across the landscape. We also found that indicators of human recreational activities negatively influenced owl distribution and habitat use. Great gray owls appear to prefer mid-elevation red fir forest with meadows that are drier and more productive in terms of small mammal populations. That these areas also have the highest human activity presents a paradox, both for individual owls and for the future conservation and management of this California endangered species. The extent to which human recreation in natural areas affects animal behavior, species distribution, and productivity is a growing issue in natural area management. We present information that will allow land managers to better understand how existing natural resources, coupled with human recreation, influence the distribution and habitat use of the great gray owl.

Explore related subjects

Natural Areas Journal Article

Source-reported bounding extent: 37.494762° to 38.185228° latitude; -119.886496° to -119.195416° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Charles van Riper, Joseph J. Fontaine, Jan W. van Wagtendonk. 2013. Great gray owls ( Strix nebulosa ) in Yosemite National Park: on the importance of food, forest structure, and human disturbance. https://doi.org/10.3375/043.033.0307

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Conducting feasibility assessments of potential conservation reintroductions: A case study with the imperiled foothill yellow-legged frog, Rana boylii

Conservation translocations are an increasingly common and often necessary component of recovering species that have become extirpated from portions of their range. Understanding and ameliorating potential threats that reduce the likelihood of successful population establishment at recipient sites is a key component of successful translocation planning. We examined multiple potential threats, including pathogens, contaminants, and invasive species, as well as habitat suitability and food resources, to assess the feasibility of reintroducing threatened, stream-obligate foothill yellow-legged frogs, Rana boylii , to Pinnacles National Park. Foothill yellow-legged frogs were extirpated from this protected area more than half a century ago. Although invasive species, disease, contaminants, food resources, and water temperatures are unlikely to inhibit foothill yellow-legged frog population establishment, potential recipient streams at Pinnacles National Park had shorter hydroperiods and much higher canopy cover than reference streams with extant foothill yellow-legged frog populations. Although the exact cause of extirpation of foothill yellow-legged frogs from Pinnacles National Park is unknown, translocations of foothill yellow-legged frogs to the park are more likely to succeed if riparian canopy cover is reduced and stream hydroperiods increased to better match those at nearby populations. Thoroughly understanding the threats to and characteristics of potential recipient sites could improve the likelihood of success of translocation outcomes in natural areas.

California↗

USGS2026

A template for integrated ecological restoration planning, implementation, and monitoring: Case study from the Little Saint Francis River Chat Pile mining site

We present here a template for integrated ecological restoration planning and monitoring, using a case study from the Little Saint Francis River chat pile restoration site in Madison County, Missouri, USA. We used US Department of Agriculture Ecological Site Descriptions (ESDs) to identify a range of potential target vegetation communities given the site's biophysical setting. Preliminary site inspection allowed qualitative assessment of current vegetation condition in relation to potential ESD community types and identification of broad restoration goals (for example, “restore woodlands”). By examining the results of the site assessment with ESD descriptions, we identified specific and achievable objectives for those goals as well as relevant metrics for monitoring vegetation change through time. Pre-restoration vegetation sampling enabled refinement of objectives and quantified conditions against which to assess change as restorations mature. Because the sampling methods were adopted to address the specific objectives for the restoration, they continue to provide the framework for monitoring vegetation changes following restoration implementation. Herein we describe how this approach was applied in each of the broad community types encountered at the Little Saint Francis River site, relating pre-restoration species abundance measures to abundance values typical of community types associated with each ESD. In so doing, we demonstrate an iterative, data-driven process that can be applied to restoration planning and monitoring in many ecological systems and restoration contexts.

Missouri↗

USGS2026

A little-known piñon from the Mogollon Highlands: Natural history of Pinus x fallax in the Prescott National Forest, Arizona, USA

The Mogollon Highlands is an area of rich biodiversity in central Arizona and western New Mexico. The piñon-juniper/chaparral in the Mogollon Highlands is unique from other piñon-juniper woodlands in both taxonomy and structure. The hybridization of the common piñon there, Pinus × fallax (Mogollon Highlands piñon, MHP), is hypothesized to render it more tolerant to heat and aridity than one of the parent plants, Pinus edulis (Colorado piñon). Yet as Climate Water Deficit continues to increase, so does concern for the future of these woodlands and the MHP. Using demographic data on MHP from the last four decades, we evaluate fecundity and mortality patterns in woodlands where MHP is co-dominant with three Juniperus species and numerous perennial shrubs. Our data indicate that MHP stands continue to reproduce and that mortality is low relative to the more northern P. edulis stands. We also present a simple calculation of historical fire rotation in Prescott National Forest woodlands, estimating a fire rotation of two centuries, far shorter than other piñon-juniper associations. We also explore fire patterns since 1985 across the ecoregion; abundant charcoal indicates small patchy fires were common. In spite of widespread fires, most Mogollon Highlands fires have occurred in Pinus ponderosa (ponderosa pine) forests, leaving piñon-juniper/chaparral intact. Together these trends indicate that MHP and associated perennial co-dominants are tolerant of current climates. We suggest that hybrid genetic combinations, the complex perennial understory (e.g., actinorhizal shrubs, rich diversity of nurse microsites), and fire patterns are responsible for this resiliency.

Arizona↗