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Duck Hawks Nesting in Colorado

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Duck Hawks Nesting in Colorado.-Although the Duck Hawk (F&o fseregrinus) has been reported nesting in two localities in Colorado, it seems desirable at this time to place on record a third and more northern nesting location in the state. Sclater (A-History of the Birds of Colorado, London, 1912) wrote of a pair that nested in the Garden of the Gods for five years. More recently Bailey and Niedrach (.4uk, 63, 1946:253) reported a pair they observed in 1943 nesting at Chimney Rock between Pagosa Springs and Durango in southwestern Colorado.

On April 25, 19.50, Victor Favier reported a hawk or falcon nest on the back of the third Flatiron, a prominent rock formation just south of Boulder. The next day he and I visited the site fully expecting to see Prairie Falcons but were surprised to find a pair of Duck Hawks with four eggs. Copulation Gas observed at this time. The nest was on a ledge about sixty feet from the ground. The site was visited on May 9, 14, and 21. It was next visited about two weeks later when three well-developed young were present. The fourth egg was infertile. The three young were banded at this time. On June 24 a young female was taken from the nest for use in falconry; this is the last time the birds were observed.

The attitude of the birds toward a pair of Prairie Falcons (F&o mexicanus) may be of interest. The nest of the Prairie Falcons was situated approximately two hundred yards from but not in direct view of the Duck Hawk site. At the time the nest of these birds was discovered it contained five young slightly older than those of the Duck Hawk. When this nest was approached the Prairie Falcons flew about noisily, much more so than we had ever seen the Duck Hawks do. At one time when I had my eyes fixed on the crying bird a Duck Hawk streaked by almost faster than my eyes could follow and only a few feet over the Prairie Falcon. This performance was repeated at least three times. This was the first time we had ever seen the Duck Hawks take any notice of the Prairie Falcons. These actions and the proximity of the two nests would seem to contradict the conjecture of Webster (Auk, 61, 1944:609-616) that the Duck Hawk has been crowded out by the Prairie Falcon as a resident breeding bird in Colorado.-NORMAN R. FRENCH, University of Colorado Museum, Boulder, Colorado, August I, 1950.

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