Geology topics

R.K. Murphy

Publications and source records attributed to R.K. Murphy.

3 recordsLinked to original sources

USGS2022

Golden eagle nesting territory distribution in wind energy landscapes of the southern Great Plains

Deaths of four Golden Eagles ( Aquila chrysaetos ) due to collision trauma at a new wind energy facility in east-central New Mexico during 2004–2005 prompted concerns about the species' population status in the encompassing Southern Great Plains region, primarily because its breeding distribution there was poorly documented and wind energy development was expanding rapidly. Therefore, we conducted aerial searches for Golden Eagle nests across northeastern New Mexico, northwestern Texas, western Oklahoma, and adjacent portions of Colorado and Kansas during 2006–2009 and 2015–2020. We delineated five Golden Eagle Nest Search Areas (NSAs) with unique physiographic/geological origins. Individual NSAs were searched partially or entirely for up to 8 yr. Collectively, we identified 123 nesting territories (NTs) occupied by Golden Eagles ≥ 1 yr, of which 94 (76%) were in northeastern New Mexico. The most NTs (40) were in the 11,720-km 2 Highlands NSA. Greatest NT density (126.6 km 2 /NT) and shortest NT nearest neighbor distance (7.4 km) were in the 3533-km 2 Northern Caprock NSA. Wind turbines existed near (within 3.2 km) eight nests distributed among five of 28 NTs in the Northern Caprock and were planned for sites in two occupied NTs. Elsewhere, only potential turbines were near nests and only within six NTs. The number of nesting territories we found underscores the importance of the Southern Great Plains to Golden Eagles, even though this region lies at the eastern margin of the species' western North American breeding range. Our data provide strong support for protecting breeding habitat from potential threats, particularly those posed by wind energy development, and are also a foundation for long-term population monitoring.

Colorado, Kansas, New Mexico, Oklahoma, Texas↗

USGS2020

Golden Eagle perch site use in the U.S. southern plains: Understanding electrocution risk

Electrocution on overhead electric systems is a primary cause of anthropogenic mortality for Golden Eagles ( Aquila chrysaetos ) in North America. Distribution poles supporting energized equipment are most often involved in electrocutions, but the frequency with which Golden Eagles perch on pole supporting equipment is unknown. To resolve questions of perch frequency, and by extension, electrocution risk and mitigation prioritization, we used Google Earth to identify perch locations of GPS-transmittered preadult Golden Eagles, and specifically to identify perching on poles supporting transformers. We used transformer poles as a proxy for electrocution risk because transformers are visible in Google Earth imagery. We examined 105 randomly selected “perch events” for each of 10 Golden Eagles ( n = 1050 perch events total) tracked for a mean of 16 consecutive mo after fledging. The most frequently used perch sites were cliffs (24.6%), trees (21.2%), and hills (16.6%). Across individuals, 10.8% of perches were on overhead electric systems (individual ranges = 0.0–34.3%). Seven Golden Eagles perched on a distribution pole at least once. Of these, five perched on a transformer pole at least once. Perching on transformer poles occurred more frequently than expected given the proportion of transformer poles present (Yates’ χ 2 = 26.5, P < 0.001). Given the frequency of perching on transformer poles revealed in this study and the frequency of electrocution on equipment poles revealed in previous studies, the data suggest that electrocution mitigation measures should be focused on equipment poles. Future research should quantify perching across a wider variety of habitats and Golden Eagle age and sex to identify whether the patterns reported here occur more broadly.

Colorado, Kansas, Nebraska, New Mexico, Oklahoma, ↗

USGS2009

An emerging crisis across northern prairie refuges: Prevalence of invasive plants and a plan for adaptive management

In the northern Great Plains, native prairies managed by the U.S. Fish and Wildlife Service (Service) can be pivotal in conservation of North America's biological diversity. From 2002 to 2006, we surveyed 7,338 belt transects to assess the general composition of mixed-grass and tallgrass prairie vegetation across five "complexes" (i.e., administrative groupings) of national wildlife refuges managed by the Service in North Dakota and South Dakota. Native grasses and forbs were common (mean frequency of occurrence 47%-54%) on two complexes but uncommon (4%-13%) on two others. Conversely, an introduced species of grass, smooth brome (Bromus inermis), accounted for 45% to 49% of vegetation on two complexes and another species, Kentucky bluegrass (Poa pratensis) accounted for 27% to 36% of the vegetation on three of the complexes. Our data confirm prior suspicions of widespread invasion by introduced species of plants on Service-owned tracts of native prairie, changes that likely stem in part from a common management history of little or no disturbance (e.g., defoliation by grazing or fire). However, variability in the degree and type of invasion among prairie tracts suggests that knowledge of underlying causes (e.g., edaphic or climatic factors, management histories) could help managers more effectively restore prairies. We describe an adaptive management approach to acquire such knowledge while progressing with restoration. More specifically, we propose to use data from inventories of plant communities on Service-owned prairies to design and implement, as experiments, optimal restoration strategies. We will then monitor these experiments and use the results to refine future strategies. This comprehensive, process-oriented approach should yield reliable and robust recommendations for restoration and maintenance of native prairies in the northern Great Plains. 2009 by the Board of Regents of the University of Wisconsin System.

Ecological Restoration↗