COMPARATIVE OOLOGY OF NORTH AMERICAN BIRDS. 477 



From this it will be seen that the eggs of Hawks may vary greatly in 

 the same genus, from an unspotted white egg (A. atricapillus) to a green- 

 ish white egg, heavily marked all over (A. velox.). 



Harris's Hawk (Parabuteo) also lays three or four eggs, whieh are 

 white or a buff white, and show more or fewer light brown markings. 

 About half the eggs of this species also lack markings. The eggs of 

 our common Red-tailed Hawk (Buteo borealis), which I have collected 

 upon numerous occasions, vary •wonderfully in point of size. There are 

 generally four to the clutch, and have a ground color of bluish white. 

 Some have spots, others are irregularly marked with various brown- 

 ish tints, which markings are of the greatest variety, no two specimens 

 being exactly alike in pattern with respect to size, color, intensity, or 

 distribution. Unspotted eggs occur in the same set with spotted ones. 

 Bendire says of the Zone-tailed Hawk (Buteo abbreviatus) that its "eggs 

 vary from 1 to 3 in number, usually 2, and seem to be for the most part 

 unspotted. They are oblong oval in shape, pale bluish white in color, 

 and the shell is rather smooth and finely granulated." (p. 233.) 



Hawks of the genus Falco as a rule lay dark-colored eggs, more or 

 less covered all over with markings of various shades of brown. Falco 

 mexicanns, however, lays from 2 to 5 creamy white eggs, more or less 

 sprinkled over with madder-brown spots and markings. Other whit- 

 ish-colored eggs of species of this genus may have the ground color al- 

 most entirely hidden or obscured by the markings being so numerous 

 and close together. The egg of the Aplomado Falcon is an instance of 

 this kind. Audubon's Caracara ( Polyborus cheriway) also lays from 2 to 

 3 eggs, which, according to Bendire, are "oval in shape; the ground 

 color, when visible, which is not often the case, is creamy white, and in 

 the majority of specimens is entirely hidden, the egg appearing to be 

 of a uniform rufous cinnamon of different shades, some of the darker ap- 

 proaching vinaceous rufous. This is again overlaid with irregular 

 blotches and spots of dark chocolate, claret, brown, and burnt umber. 

 Most of these eggs are heavily marked, a few, however, only slightly, 

 and in these the markings are usually small and more regular in out- 

 line, a few are unspotted, and although the ground color is not visible it 

 is entirely overlaid with an even-colored cinnamon tint." (pp. 317, 318.) 

 It would be impossible here, without far exceeding the limits of space, 

 to begin to describe the eggs of the Osprey (Pandion). They are all 

 wonderfully handsome, but vary in size, form, ground colors, and mark- 

 ings to an endless degree. To view Capt. Bendire's beautifully-colored 

 figures of them (PI. xi) one can hardly believe that they were laid by 

 the same species of bird. Still the eggs of Polyborus shown upon the 

 same plate vary quite as much and in the same particulars, and even 

 more so in the matter of size. 



Eagles, as in the case of the Falcons and Hawks, lay but few eggs, 

 rarely more than three, and they also range from a pure white egg 

 {Halice'etus leucocephalus) tooneshowing upon its surface speckles, spots, 



