Here is a half shell from the first hatch of Rufous & Henrietta this year. I was surprised to find it is almost as large as a hen egg. The eggshell measured almost 1-1/2" in diameter. (Hen egg shown left; Cooper's hawk egg on right.)
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Here is more information on Cooper's Hawk eggs from Smithsonian Library:
The eggs of a set vary in number from three to six, four being the usual complement. The shell is somewhat granular, and varies in color from chalky white to a faint greenish-blue. Ordinarily it is tinted with greenish-blue. Sometimes the tint is of different intensity in different parts of the same egg. The markings consist of blotches, spots, and, occasionally, streaks of brown. Usually the marks are very indistinct, and may easily be overlooked. Sometimes the brown is decided. The markings are most abundant about the base. Some eggs are entirely unmarked. In size the eggs average about 1.48 x 1.90. According to Dr. Brewer, eggs of this species vary from 1.50 to 1.60 in short-diameter, and from 1.85 to 2.00 inches in long-diameter. Dr. Coues, in "Birds of the North-West," gives the variations from 1.80 to 2.10 in long-diameter, and from 1.55 to 1.60 in short-diameter. A set of eggs collected by Mr. Chas. Dury of Cincinnati, measures respectively 1.45 x 1.90, 1.46 x 1.87, and 1.46 x 1.88. Incubation is said to last twenty-seven days.
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Fri Mar 22, 2013 1:31 pm
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