Date of Award:

5-1-1988

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Biology Ecology

Committee Chair(s)

James A. Gessaman

Committee

James A. Gessaman

Committee

Keith Dixon

Committee

Ivan Palmblad

Committee

Don Sisson

Abstract

Measurements from more than 5,000 Sharp-shinned Hawks, Accipiter striatus, Cooper's Hawks, A. cooperii,, and Northern Goshawks, A. gentilis, trapped on the Goshute Mountains of eastern Nevada, were compiled. New species identification and sexing criteria were derived for accipiters in western North America. Goshute migrants averaged proportionately the longest wings and tails but weighed Jess than migrants from Marin Headlands, CA, Cedar Grove, WI, and Cape May Point, NJ. Interior migrants averaged less weight and longer wings and tails than coastal migrants. It is suggested that low flight-loading might be adaptive for migrating long distances, inhabiting open country, or in regions of high altitude or thermal production. Fifteen measurements were taken from over 500 Sharp-shinned and Cooper's hawk museum specimens, collected during the breeding season. Methods were developed to adjust specimen measurements for wear of feathers, age dimorphism, and drying of museum specimens, and the significance of these problems was analyzed. A rigorous test of the hypothesis that comparative morphometrics could be used to identify the approximate breeding ground origins of Goshute migrants was not possible; there were too few specimens. However, some consistent, general patterns of geographic variation were elucidated, using Principal Components Analysis and contour mapping, and these yielded some insight about the possible origins of Goshute migrants. Overall size, the length of the wings and tail relative to the size of other appendages, and the shape of the wings were the most important sources of variation. Overall size variation of Sharp-shinned Hawks conformed to Bergmann's Rule. The smallest Cooper's Hawks were associated with the Rocky Mountain complex. Long, swept-back wings and long tails were most characteristic of hawks from the dry, open country of the eastern Great Basin and southern Rocky Mountain region. These trends suggested that northern Sharp-shinned Hawks do not migrate farther south than southern breeders, and that most Goshute migrants probably originate from the central Rocky Mountains and farther south in the drier, more open forests of interior Oregon, Washington, Idaho, and the eastern Great Basin.

Download

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .