Aubrey Valley is approximately 46 km northwest of Seligman, AZ, adjacent to historical Route 66. This site is home to Arizona?s largest colony of Gunnison?s prairie dogs (Cynomys gunnisoni), and for this reason it was also designated as a reintroduction site for black-footed ferrets. The large prairie dog population also provides a regional prey base for resident and migrating raptors, including Golden Eagles (Aquila chrysaetos) and Ferruginous Hawks (Buteo regalis) as well as synoptic species like Burrowing Owls (Athene cunicularia). The extensive north-south cliff line provides abundant raptor nesting and perching opportunities.

Ornithological Summary

Aubrey Valley is extremely important for birds, especially raptors, because it juxtaposes important landscape features along with vital biotic community resources raptors need to survive. Sixteen species of raptor have been found here by surveyors during transects and point counts. The valley has abundant small-mammal species, including a large colony of prairie dogs, cottontail rabbits (Sylvilagus audubonii), and jackrabbits (Lepus californicus). These provide food for numerous resident and migratory raptorial species. Aubrey Cliffs, the most prominent feature on the landscape, rises approximately 300 m from the valley floor and provides ideal habitat for species such as Golden Eagles (high of 24/survey), a species of high conservation status (SGCN Tier 1b, USFWS BBC BCR 16). Survey data also shows this area to support high numbers of Ferruginous Hawks (high of 23/survey) at certain times of the year, also a species of high conservation status (IUCN Near Threatened, SGCN Tier1b and USFWS BCC 16). Although no systematic raptor nest searches have been conducted, regional biologists have documented at least one Golden Eagle nest territory and one Ferruginous Hawk nest confirmed as active. The road transect data indicates the area is a significant post-breeding dispersal and migration corridor for these two species. Other raptors are also very abundant in the area, notably Red-tailed Hawks and American Kestrels. Burrowing Owls are prevalent throughout the valley, and are consistently seen during Black-footed Ferret spot-light surveys. Out of 129 surveys, 377 Burrowing owls were opportunistically observed.

Conservation Issues

The largest potential threat to birds in Aubrey Valley is the proposed wind farm that will put electricity-generating wind turbines on the Aubrey Cliffs. The large abundance of raptors in the area would be at risk for collisions with the large rotating turbine blades. Visual and auditory disturbance may displace birds into less suitable habitat which could reduce their survivability and nesting success. Construction of the towers would also impact a considerable amount of the pinion-juniper habitat that exists on the ridge. This habitat is likely used by both raptors and songbirds for nesting. Nesting birds could be displaced by the construction of the towers and/or killed by colliding with the rotating blades.

Ownership

The Aubrey Valley is part of the Diamond A Ranch and is comprised of checkerboard State Trust and private land owned by the Navajo Nation. Primary and historic use is cattle grazing with grazing rights currently leased to the Cholla Cattle Company. Aubrey Valley is also used as a reintroduction site for black-footed ferrets (Mustela nigripes).

Habitat

Brown (1982) characterizes Aubrey Valley as a Plains and Great Basin Grassland Community, with annual precipitation averaging 25 to 30 cm. It is dominated by high elevation grassland in the valley floor and pinyon-juniper among the ridges. This site also contains approximately 25 km of exposed cliff face that follows a northwest-southeast axis.

Land Use

Primary and historic use is cattle grazing with grazing rights currently leased to the Cholla Cattle Company. Aubrey Valley is also used as a reintroduction site for black-footed ferrets (Mustela nigripes).

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