Education
Ph.D. Forest Ecology, Oregon State University, 2004
Specialty
Habitat relationships of forest birds
Oregon white oak communities
Research Interests
Forest and wildlife ecology
Wildlife-habitat relationships
Restoration of native habitats
Great Basin pygmy rabbits
Accurately quantifying and mapping wildlife habitat is critical to investigations of species distribution and habitat relationships, and can greatly facilitate management of forests for multiple resources. However acquiring field-based, empirical data is often costly and labor intensive. Modeling provides an alternative technique for describing and mapping habitat, but the usefulness of models...
Conifer forests in the Pacific Northwest are biologically and economically important, are intensively managed for multiple uses, and represent a large area in public domain. Therefore, understanding how management of conifer forests affects biodiversity across a range of spatial and temporal scales is critical for land management agencies.
Special status species and habitats are often sentinels of accelerated ecosystem change and, by definition, are priorities for protection, restoration, or focused management.
Climate change has been implicated in the range shifts and population declines of many species, but the confounding of climate change with other variables, particularly landscape change, hampers inference about causation. Climate envelope models have been used to predict population trends and future distributions, but the reliability of such predictions remains relatively unknown; without...
We measured characteristics of 731 snags and quantified foraging and breeding use of snags by birds 25-27 years after their creation, and examined whether different harvest treatments (i.e., group selection, two-story, clearcut) and snag configurations (i.e., scattered and clustered) influenced snag characteristics or avian use for foraging and nesting.
This dataset includes two spreadsheets: The "Avian_abundance_oak_mistletoe_bird_data" spreadsheet contains data regarding Oregon White Oak tree (Quercus garryana) measurements. The "Avian_abundance_oak_mistletoe_surveys_data" spreadsheet contains bird survey observations.
The western purple martin (Progne subis arboricola), an avian insectivore, is a species of conservation concern throughout the Pacific Northwest. Compared to the well-studied eastern subspecies (Progne subis subis), little is known of the life history and biology of the western subspecies. Availability of breeding habitat is believed to be a major...
Sherman, Lorelle M.; Hagar, Joan
The western subspecies of the purple martin (Progne subis arboricola) is currently listed as a “critically” sensitive species in four ecoregions of western Oregon: Coast Range, Klamath Mountains, West Cascades, and Willamette Valley (Oregon Department of Fish and Wildlife, 2019). Importantly distinct from the abundant and widespread eastern...
Hagar, Joan; Branch, Eric Livestock grazing is the most prevalent land use practice in the western United States and a widespread cause of degradation of riparian vegetation. Riparian areas provide high-quality habitat for many species of declining migratory breeding birds. We analyzed changes in vegetation and bird abundance at a wildlife refuge in southeastern Oregon...
Poessel, Sharon; Hagar, Joan; Haggerty, Patricia; Katzner, Todd E. Land management practices often directly alter vegetation structure and composition, but the degree to which ecological processes such as herbivory interact with management to influence biodiversity is less well understood. We hypothesized that large herbivores compound the effects of intensive forest management on early seral plant communities...
Stokely, Thomas D.; Verschuyl, Jake; Hagar, Joan; Betts, Matthew G. Snags are important habitat features for many forest‐dwelling species, so reductions in the number of snags can lead to the loss of biodiversity in forest ecosystems. Intentional snag creation is often used in managed forests to mitigate the long‐term declines of naturally created snags, yet information regarding the use of snags by wildlife...
Barry, Amy M.; Hagar, Joan; Rivers, James W.
Habitat models using lidar-derived variables that quantify fine-scale variation in vegetation structure can improve the accuracy of occupancy estimates for canopy-dwelling species over models that use variables derived from other remote sensing techniques. However, the ability of models developed at such a fine spatial scale to maintain accuracy...
Hagar, Joan C.; Aragon, Ramiro; Haggerty, Patricia; Hollenbeck, Jeff P. Snags provide essential habitat for numerous organisms and are therefore critical to the long-term maintenance of forest biodiversity. Resource managers often use snag creation to mitigate the purposeful removal of snags at the time of harvest, but information regarding how created snags change over long timescales (>20 y) is absent from...
Barry, Amy M.; Hagar, Joan; Rivers, James W. This dataset includes two spreadsheets: The "Avian_abundance_oak_mistletoe_bird_data" spreadsheet contains data regarding Oregon White Oak tree (Quercus garryana) measurements such as height, diameter and crown volume along with microhabitat data including number of mistletoe infections, number of cavities, amount of dead wood, amount of loose/...
Pritchard, Kyle R.; Hagar, Joan; Shaw, David C. Mistletoes are parasitic or hemi-parasitic flowering plants that parasitize woody plants around the globe. Important food and cover resources provided by mistletoes have been related to strong patterns of positive association between wildlife diversity and mistletoe density. Mistletoes also create microhabitat features known to be important to...
Pritchard, Kyle R.; Hagar, Joan; Shaw, David C. Natural Resource Condition Assessments (NRCAs) evaluate current conditions for a subset of natural resources and resource indicators in national parks. NRCAs also report on trends in resource condition (when possible), identify critical data gaps, and characterize a general level of confidence for study findings. The resources and indicators...
Hoffman, Robert; Woodward, Andrea; Haggerty, Patricia K.; Jenkins, Kurt J.; Griffin, Paul C.; Adams, M.J.; Hagar, Joan; Cummings, Tonnie; Duriscoe, Dan; Kopper, Karen; Riedel, Jon; Marin, Lelaina; Mauger, Guillaume S; Bumbaco, Karen; Littell, Jeremy S. 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...
Hagar, Joan C.; Eskelson, Bianca N.I.; Haggerty, Patricia K.; Nelson, S. Kim; Vesely, David G. Natural Resource Condition Assessments (NRCAs) evaluate current conditions for a subset of natural resources and resource indicators in national parks. NRCAs also report on trends in resource condition (when possible), identify critical data gaps, and characterize a general level of confidence for study findings. The resources and indicators...
Hoffman, Robert; Woodward, Andrea; Haggerty, Patricia K.; Jenkins, Kurt J.; Griffin, Paul C.; Adams, M.J.; Hagar, Joan; Cummings, Tonnie; Duriscoe, Dan; Kopper, Karen; Riedel, Jon; Samora, Barbara; Marin, Lelaina; Mauger, Guillaume S.; Bumbaco, Karen; Littell, Jeremy S.
In this episode we sit down with USGS wildlife biologist Joan Hagar and discuss her recent study on songbirds in the Pacific Northwest. New research indicates a possible relationship between reductions in the abundance of some species of songbird and reductions in the amount of deciduous trees in evergreen forests. Join us, as we demonstrate how Oregon songbirds sing for
The western purple martin is a species of conservation concern throughout the Pacific Northwest.
Livestock grazing can degrade riparian vegetation, altering habitat for many species of declining migratory breeding birds. At Hart Mountain National Antelope Refuge in southeastern Oregon, cattle were removed from riparian areas in 1990 after 120 years of grazing.
The development of metrics derived from LiDAR to study forest structure has advanced wildlife-habitat modeling.
Land management practices often directly alter vegetation structure and composition, but the degree to which ecological processes such as herbivory are affected is poorly understood.
Managers often intentionally create snags to mitigate the long-term declines of natural snags, yet information regarding use of created snags by wildlife across long timescales is lacking.