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Breeding chronology, molt, and measurements of accipiter hawks in northeastern Oregon

Journal of Field Ornithology

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Abstract

Most northern goshawks completed laying eggs in April, while most Cooper's hawks completed their clutches in May with essentially no overlap. The sharp-shinned hawks laid in late May and June. Juvenile females represented 4% of the northern goshawk breeding population; 22% of the Cooper's hawk breeding population (highest reported for the species) and 60% of the sharp-shinned hawk breeding population, northern goshawks and Cooper's hawks in juvenal plumage generally nested later in the season, but not sharp-shinned hawks. Females of each species began molting first. Primaries were molted from the innermost outward in all species, but rectrix molt sequence was variable. Usually R1 was molted first. Primary molt of the 2 wings was usually synchronous; however, the rectrix molt was not as orderly. Arrested molt was observed in some individuals of all species; it probably has an energy-saving function. Wing chords of adult northern goshawks from Oregon were not different from Wisconsin fall migrants or birds from Alaska; however, rectrices were significantly shorter in Oregon than Wisconsin. Cooper's hawks nesting in Oregon were much smaller than those trapped in Wisconsin. Wing chords and rectrices were significantly shorter for both sexes, and, although weights were not directly comparable, Oregon Cooper's hawks also weighed much less. The limited number of sharp-shinned hawks measured precluded statistical analyses.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Breeding chronology, molt, and measurements of accipiter hawks in northeastern Oregon
Series title:
Journal of Field Ornithology
Volume
56
Issue:
2
Year Published:
1985
Language:
English
Contributing office(s):
Patuxent Wildlife Research Center
Description:
97-112
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Field Ornithology
First page:
97
Last page:
112
Number of Pages:
16