Common Raven (Corvus corax) Abundance in
Relation to Anthropogenic Resources within the Idaho National
Laboratory Site in 2010
This study examines how proximity to anthropogenic resources affects common raven abundance. Determining how anthropogenic resources influence raven density in sagebrush steppe habitat will provide Bureau of Land Management (BLM) land managers with information necessary to identify sources of human disturbance. Specific objectives include the following:
Calculate resource selection functions of habitat use for territorial and non-territorial ravens on the INL Site
Develop predictive model of broad-scale raven habitat use
Identify anthropogenic factors that affect raven presence.
Common raven (Corvus corax) populations in the western United States have increased
substantially during the last 50 years. Ravens typically are more abundant in human-altered
landscapes than in intact ecosystems. This is cause for concern among land managers because
ravens are considered a synanthropic predator (a predator benefi ting from anthropogenic
resources and land actions) of numerous sensitive species, including Greater Sage-Grouse
(Centrocercus urophasianus) eggs and chicks. Increases in linear infrastructures (roads and
power lines) are likely to further increase raven abundances and subsequently increase sagegrouse
nest depredation by ravens. The potential for ravens to limit sage-grouse populations
constitutes a need to assess the presence of ravens over large spatial scales within sagebrush
For surveyed ravens, the simplest and most meaningful models included distance from
transmission lines, facilities, and non-native grasslands. For every 1 km (0.6 miles) increase
in distance to transmission lines and facilities, the odds of raven presence decreased by 9.3
percent and 4.5 percent, respectively. Also, for every 10 ha (25 acre) increase of non-native
vegetation, the odds of raven presence increased by 2.7 percent. In post hoc analyses, the
odds of raven presence increased with greater habitat edge length of big sagebrush (Artemisia
tridentata spp.) and non-native vegetation.
For nesting ravens, the odds of nesting were greater with decreased distance to transmission
lines and increased amount of vegetation type edge. For every 1 km (0.6 miles) increase in
distance away from a power line there was a 37 percent decrease in odds of raven nesting.
Habitat fragmentation indices were 3.1 times greater at nest sites than at random sites. For
every 100 m (328 feet) of added vegetation edge, there was an estimated 20 percent increase in
the odds of raven nesting.