HWI Public Comments (4)

HawkWatch International conducted a study, funded by the Bureau of Land Management (BLM), to assess the ability of perch deterrents to limit raptor and raven perch use on a new power line constructed in southwestern Wyoming.  The results are published in the July 2010 edition of the Journal of Wildlife Management.

THE PROBLEM:
In open habitats, power line poles and other support structures provide attractive perches for raptors and ravens where few natural perches exist.  The study area is home to many species of management concern, including the Greater Sage Grouse, Sage Thrasher, and Pygmy Rabbit, due to recent declines in their populations and threats to their persistence.perch_deterrant

THE QUESTION:
Were perch deterrents effective in excluding raptors and ravens that may be attracted to and concentrate around the new power lines perches?

THE STUDY:
Three types of surveys were conducted along both the “deterrent” line and a control line (no deterrent device) between September 2006 and August 2007 in order to monitor raptor and raven activity.

1.  Driving surveys were conducted along roads parallel to the power lines at a predefined speed during which the observer simply scanned the power poles for any perched birds; when seen, they stopped and recorded information, including species, location, behavior, etc.

2.  Behavioral observation surveys were conducted for 1 hour periods where the observer sat at a pre-selected point and watched a segment of the powerline for any activity.  Their survey “window” was the pole directly in front of them and three on either side, seven poles in total.

3.  Prey-remains surveys consisted of searches under three pre-selected poles for any pellets or prey remains within a 10 meter radius of the poles.

THE RESULTS:
Each of the three survey types showed that raptor and raven activity was significantly lower on the deterrent line, but perching was not prohibited entirely.

During 192 driving surveys along each line, only 42 raptor and raven sightings were noted on the deterrent line, compared to 551 sightings on the control line.

The behavioral studies recorded 31 deterrent line behaviors and 124 control line behaviors during 192 hours of observation.  The behaviors were mostly general perching, flights to and from perches, and flights through the observation area.

Results from 576 prey-remains surveys near each line noted 17 single prey items and 65 grouped items near the deterrent line compared to 398 single prey items and 493 grouped items near the control line

THE BOTTOM LINE:
Overall, our results suggest that perch-deterrent devices can reduce raptor and raven activity

on power-line structures, but to determine their utility on entire power-line segments, we suggest managers consider 1) what level of reduction in perch activity is worth the cost, and 2) the availability of alternate perches in the surrounding landscape.

 

HWI recently completed a comprehensive report based on annual raptor nest surveys in northwestern Utah from 1998-2007.  The objective of this report was to provide land managers with baseline raptor inventory and nest-monitoring data from the region and establish a scientifically defensible basis for making management decisions that help maintain ecosystem integrity and the area’s nesting raptors.  The data resulted in some significant findings and management recommendations.  For the full report, click here.

SPECIES OF FOCUS AND DESIGNATIONS:IMG_1471

  • Golden Eagle (Aquila chrysaetos)
  1. Although Golden Eagles are not yet afforded any special status, long-term nesting studies in the Snake River region of Idaho and in north-central Utah, as well as regional migration-count indices, confirm significant declines in nesting activity and overall populations, with large-scale loss and degradation of native shrubsteppe habitat believed to be the principal cause of declines in the Intermountain region.
  • Ferruginous Hawk (Buteo regalis)
  1. Listed as a Wildlife Species of Concern in Utah
  2. Recognized by the PIF North American Landbird Conservation Plan for the Basin & Range Physiographic Area as priority species in relation to conservation of shrubsteppe, sagebrush grassland, and pinyon-juniper habitats
  • Red-tailed Hawk (Buteo jamaicensis)
  • Swainson’s Hawk (Buteo swainsoni)
  1. At the onset of the study listed as a species of concern in Utah and it is still recognized as a Partners in Flight (PIF) Continental Watch List species
  2. Recognized by the PIF North American Landbird Conservation Plan for the Basin & Range Physiographic Area as priority species in relation to conservation of shrubsteppe, sagebrush grassland, and pinyon-juniper habitats
  • Peregrine Falcon (Falco peregreinus)
  • Prairie Falcon (Falco mexicanus)
  1. Recognized by the PIF North American Landbird Conservation Plan for the Basin & Range Physiographic Area as priority species in relation to conservation of shrubsteppe, sagebrush grassland, and pinyon-juniper habitats
  • Burrowing Owl (Athene cunicularia)
  1. Listed as a Wildlife Species of Concern in Utah

 

STUDY AREA:gbrns_web_map

  • The study area in northwestern Utah was roughly bounded to the south by I-80, to the north by the Idaho border, to the west by the Nevada border, and to the east by the western margins of the Great Salt Lake.

 

CONCLUSIONS AND MANAGEMENT IMPLICATIONS:

Based on the results of the long-term surveys, HWI recommends:

  • The importance of a territory focus for the monitoring and/or protection of nesting raptors, as individual nests typically are not independent entities.  Additionally, our documentation of both regular inter-annual nest fidelity and gaps in activity of three or more years has important implications for the management of individual nests.  Our results suggest that extending 5-years of protection to inactive nests (from the last documented activity) may be a reasonable management prescription; however, longer between-use intervals are fairly common.  More importantly, we strongly encourage adoption of standards that stipulate equivalent protection for all known alternate nests within a territory regardless of which nest was used most recently.
  • Highlights the difficulties of adequately monitoring Burrowing Owls with typical, community-level raptor nest-monitoring protocols.  We suggest that, in the absence of a more advanced understanding of individual territory dynamics, surveyors focus on the overall occupancy, activity, etc. of entire “burrow complexes” (i.e., spatially clumped burrows distinct from other burrow clumps). 
  • We suggest that local land managers pay particular attention to the relatively high raptor nesting activity in the Grouse Creek Valley and Prohibition Springs area, and consider educating local private landowners about the importance of their lands for nesting raptors.
  • Additional research into the complicated relationships between invasive vegetation and Ferruginous Hawk and Burrowing Owl nesting ecology warrant further investigation
  • Further advance our collective, detailed understanding of the ecology of the northwest Utah raptor community, which will require the addition of an extensive and rigorous program to simultaneously monitor prey abundance in the region.