Date of Award:

1988

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Natural Resources

Advisor/Chair:

Gar W. Workman

Abstract

This study examined the effects of habitat parameters, disturbances and predation on the reproductive success of golden eagles (Aguila chrysaetos), ferruginous hawks (Buteo regalis), red-tailed hawks (Buteo jamaicensis) and prairie falcons (Falco mexicanus) in the desert area southwest of the Great Salt Lake in northwestern Utah. The prairie falcon was the only species examined that had a normal reproductive output during the study years of 1984-1986. The prairie falcon was better able to utilize the avian prey species which were very difficult for the larger and slower raptor species to capture. During the reproductive period prairie falcons used Townsend ground squirrel (Sperrnophilus townsendii) heavily. The golden eagles, ferruginous, and red-tailed hawks were not able to obtain sufficient numbers of their primary prey species, the cottontail rabbit (Sylvilagus nuttallii) and black-tailed jackrabbit (Lepus californicus), to allow for a normal reproductive output. These prey species were at the low point of their cyclic population pattern. Disturbance to raptors was not an important factor on this remote study area. Predation, primarily terrestrial mammals, did have a negative effect on reproductive success; however, it was not a major consideration due to lack of predator access on most of the cliff nesting sites of the golden eagle, red-tailed hawk, and prairie falcon. Predation appeared to have a greater impact on the ferruginous hawk nesting success as their nest sites were normally accessable to mammalian predators. Raptor nest site exposure was unimportant to nesting raptors. The nest exposure was very similar to the exposure ratio of the available cliff sites.

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