Wildlife conservation in the Willamette Valley’s remnant prairie and oak habitats

Oregon white oak (Quercus garryanna) and prairie plant communities of Oregon’s Willamette Valley are one of the most imperiled vegetation types in North America, yet few studies have been conducted on wildlife in these plant communities. The primary goal of our synthesis is to help guide future conservation and restoration efforts of these important wildlife habitats in the Willamette Valley. We synthesize relevant research and discuss future research and monitoring challenges and needs. We identify several species that are strongly associated with these habitat types in the Willamette Valley, and highlight their ecology and conservation. Our synthesis is intended for managers and researchers working to improve oak and prairie habitats for wildlife in the Willamette Valley. The project was sponsored by the Interagency Special Status Sensitive Species Program (ISSSSP) of the Pacific Northwest Regional Office of the U.S. Forest Service and Oregon/Washington State Office of the Bureau of Land Management. Oak and prairie habitats are managed as wildlife habitat by the Eugene and Salem Districts of the Bureau of Land Management in Oregon and this synthesis is intended to help guide their efforts as well as other efforts to restore oak and prairie vegetation communities for wildlife habitat in the Willamette Valley.

Despite the large loss of oak and prairie plant communities in the Willamette Valley, there have been surprisingly little research conducted on the ecology of wildlife in these habitats. What was most striking to us in our review was the large number of in-depth studies of butterfly response to restoration and the paucity of studies of vertebrates that went beyond distributional surveys. Almost all of the vertebrate studies remained descriptive, without understanding potential consequences under different management scenarios. Several studies on Fender’s blue butterfly seemed particularly valuable as a model for linking field studies with management. Developing management-oriented models can provide useful heuristic tools for identifying research needs.

The lack of experimentation and formal sampling designs in most of the studies on vertebrates that we reviewed highlights the differences with studies conducted on butterflies and restoration in the Willamette Valley. The majority of studies on vertebrates have used informal sampling approaches to investigate habitat associations at relatively small spatial scales. Understanding habitat relationships to guide restoration is difficult and traditional approaches may not be as useful as other approaches that may involve case studies, adaptive management, and indicator variables that respond to smaller-scale changes from restoration.

Research on how vertebrate wildlife responds to restoration in the Willamette Valley is challenging for four primary reasons: (1) disconnect of spatial scale of restoration and animal use patterns, (2) the high variability within and among restoration units and the typical lack of control (non-restored) areas, (3) the extremely high variability of numerous elements of habitat characteristics at the spatial scale of the landscape, making it difficult to detect larger scale patterns, (4) time lags of restoration activities and habitat response, and (5) the existence of non-habitat factors that affect bird occurrence and abundance in the restored areas.