Assessment of Chukar and Gray Partridge Populations - Idaho Power

Hells Canyon Chukar and Gray Partridge Report, Ratti and Giudice 47concluded that partridge populations in Hells Canyon during 1999 and 2000 were best classifiedas “abundant.” We did not detect any obvious problems with birds that were examined. (e.g.,external parasites, other signs of disease, body condition, etc.), and coveys seemed to be evenlydistributed throughout the study area. Mean covey size was consistent with data from othergeographic regions, which indicated that reproductive success and its determinants (clutch size,hatching success, and brood survival) were probably average. However, additional research isneeded, especially in Hells Canyon with focus on comparative ecology of the 2 species.Habitat quality in Hell Canyon also seemed to be relatively good. Although somespecific sites were classified as poor, most areas surveyed were classified as good or excellenthabitat for chukar and gray partridge. Rigorous research is also needed on habitat use, selection,and requirements in Hells Canyon. Such research will provide land managers with the necessaryinformation for proper habitat management, which will help safeguard and maintain healthypopulations of partridge. These data are also needed to fully understand direct and indirecteffects of livestock grazing on habitat.6.3. Relative significance of natural and anthropogenic limitingfactors in Hells Canyon.As noted several times on related topics, it is difficult to assess limiting factors, especiallyin Hells Canyon, given the lack of good research information on partridge. However, we canmake a number of speculative comments based on the limited local data available, data fromother regions, research on other gallinaceous species, and from our general experiences withupland birds.Among natural limiting factors we must consider those that affect recruitment andmortality. Precipitation affects vegetation, and vegetative cover and quality is directly related tooverall recruitment. Habitat conditions also influence food availability, predation vulnerability,and effects of harsh winter weather. Thus, we would predict population fluctuations are relatedto precipitation (timing and amount) and temperature in spring-summer, and winter severity(which is commonly noted for many wildlife species). In the long term, if predictions of climatewarming are correct, we may observe warmer winter conditions, which may reduce winter stress.But warmer climate may also result in less annual precipitation, which may reduce grass coverand allow drought tolerant weeds and other species to dominate. Such changes could greatlyreduce populations to levels below current trends.As noted above, loss of bunchgrass habitats and recent invasions by 2 exotic plants,yellow-star thistle and medusahead, may threaten long-term viability of chukar populations (butsee BLM data and observations of Craig Johnson, 4.10.6.1.). Data on this issue with graypartridge are lacking. We also noted above that in Washington, the greatest declines in chukarpopulations over the last 6 years have occurred in areas infested with yellow-star thistle. Thus,research on this question is needed (including adaptive management or manipulativeexperiments).