| Abstract |
- Distribution of nests and nesting success were determined for
sharp-shinned hawks (Accipiter striatus) Cooper’s hawks (A. cooperii),
and goshawks (A. gentilis) in Oregon during 1969 through 1974. 1n
addition, two areas (11,74l hectares in Eastern Oregon and 9,284 hectares
in Western Oregon) were searched intensively for nests to determine
nesting density of each species. During these years 16 A. striatus nests,
42 A. cooperii nests, and 81 A. genti1is nests received surveillance.
Both A. striatus and A. ccooperii nested in all forested areas included
in this study and A. gentilis nested in all areas except the Coast Range
in Western Oregon. In the intensively searched area in Western Oregon
four A. cooperii nests (one nest/2,32l hectares) were located in 1970
and five nests in 1971 (one nest/1,857 hectares). In 1914 four
A. striatus nests (one nest/2,750 hectares), five A. cooperii
(one nest/2,2OO hectares), and four A. gentilis nests (one nest/2750
Hectares) were located in the intensively searched area in Eastern
Oregon. Pairs of accipiters were first noted at their nest sites as
early as: 9 May, A. striatus, 28 March, A. cooperii, and 23 March,
A. gentilis. Mean date of clutch completion was: A. striatus, 26 May,
A. cooperii, 13 May, and A. gentilis, 6 May. Incubation period was
determined to be approximately 30 to 32 days for each species. Mean
clutch size was: A. striatus, 4.6 eggs, A. cooperii, 3.8 eggs, and
A. gentilis, 3.2 eggs. Mean number of young fledged per nest was:
A. striatus, 2.7 young, A. cooperii, 2.1 young, and A. genti1is 1.7 young. An analysis of hatching success, fledging success, and number
of nests that were successful showed that A. striatus suffered the
greatest losses during the incubation period, and A, cooperii and
A. gentilis during the nestling period.
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