Commissary Ridge Raptor Migration Project
HWI has been monitoring raptor migrations in North America since the late 1970s. In 2009, HWI conducted or co-sponsored 10 long-term, standardized migration counts in 8 states and Veracruz, Mexico. The primary objective of these efforts is to track long-term population trends of diurnal raptors throughout primarily western North America. Raptors feed atop food pyramids, inhabit most ecosystems, occupy large home ranges, and are sensitive to environmental contamination and other human disturbances. Therefore, they serve as important biological indicators of ecosystem health. Moreover, due to the remoteness and widespread distribution of most raptor populations, migration counts likely represent the most cost-effective and efficient method for monitoring the regional status and trends of multiple raptor species.
To be effective for regional monitoring of broadly distributed species, migration monitoring must involve a network of well-distributed, standardized counts that effectively sample all major flyways and known sub-populations. Currently, no long-term raptor migration surveys are being conducted in the state of Wyoming, and coverage of the central Rockies between Montana and New Mexico is generally sparse. Moreover, exploratory surveys conducted by HWI during 1997 in southwestern and southern Colorado generally failed to reveal concentrations worthy of additional attention. Hence, in 2000 HWI expanded its exploratory efforts to 26 sites across Wyoming and southern Montana. This fall survey concentrated on the prominent mountains of western Wyoming, but also included many more isolated ranges throughout the state and adjacent portions of southwestern Montana.
The 2000 surveys revealed potential concentrations worthy of additional attention in the southern Wind River Range of central Wyoming, and on Commissary Ridge and in the Salt River Range of western Wyoming. The southern Wind River area appeared of particular interest because of the volume of Golden Eagle migration (125 birds in 3 days), whereas the other two sites showed higher overall volume with greater diversity. Thus, during fall 2001, HWI conducted a second round of more intensive counts at these three locations to verify whether the activity in these areas warranted long-term monitoring.
Twenty-two days of counts in 2001 at Commissary Ridge (located about 25 miles north Kemmerer, WY) yielded 1,685 migrants of 17 species. Five species comprised 79% of the total: Red-tailed Hawk (19%), Sharp-shinned Hawk (18%), Golden Eagle (17%), Cooper's Hawk (15%), and American Kestrel (10%). The combined-species average passage rate of 115 birds per 10 hrs. of observation ranked high among other long-term HWI fall-migration projects in the West. Moreover, because the 2001 count at Commissary resulted from a single- as opposed to two-observer (standard at all established HWI sites) effort, it is very likely that a full-season, two-observer count at Commissary Ridge would have yielded a higher-perhaps much higher-passage rate. The other two sites monitored for a second time in 2001 yielded comparatively low passage rates. Moreover, of the three sites explored in 2001, Commissary Ridge was by far the most accessible and logistically well suited to establishment of a long-term operation.
Accordingly, during fall 2002 HWI conducted the first full-season count at Commissary Ridge (27 August - 29 October). An intense wildfire unfortunately precluded access to the site for 12 days in early September; nevertheless, despite this 12 day hiatus, our observers (most notably long-time affiliate Mike Neal) tallied more than 3,300 migrants and yielded an overall passage rate that ranked second highest among HWI's western sites in 2002 (excluding Texas and Veracruz). Since then, HWI has continued full-season counts each year with plans to continue this program as a long-term venture. In 2004, we also initiated an exploratory banding program at the site, and have since continued this effort annually, finally settling on two permanent trapping stations in 2007.
Visitors are welcome at this site at all times. For those interested in overnight stays, there are plenty of remote camping options near the site or in the valley below along the Hams Fork River, a developed campground about 15 miles north along the Hams Fork River, and several motel options in Kemmerer within 25 miles of the site.
Financial and logistical support for this project in 2009 was provided by the Bureau of Land Management - Kemmerer Field Office, the Walbridge Fund, and HWI private donors and members. We also thank Einstein Bagels and Salt Lake Roasting Company of Salt Lake City for supplying our crew with much appreciated supplies.