214 BULLETIN 16 7, UNITED STATES NATIONAL MUSEUM 



granulated. The color is dead white or faintly bluish white. They 

 are usually entirely unmarked, but apparently some are faintly and 

 sparingly marked with small spots of pale lavender or pale yellowish 

 brown, sometimes concentrated about one end or the other. Some 

 collectors claim that this hawk never lays spotted eggs, but I see no 

 reason why it should not do so occasionally, as the marsh hawk and 

 Cooper's hawk are known to do. J. H, Bowles writes me that he has 

 a slightly spotted set, the parents of which were shot. The eggs that 

 we collected in Arizona were unmarked, and I have another unmarked 

 set in my collection. Any eggs supposedly of this species that are 

 heavily marked are probably referable to the Mexican black hawk. 

 Major Bendire (1892) discusses this question quite fully. The 

 measurements of 37 eggs average 55.6 by 43.5 millimeters ; the eggs 

 showing the four extremes measure 63 by 45, 56 by 49.6, and 52.4 by 

 38.9 millimeters. 



Young. — That both sexes incubate has been definitely proved. In- 

 cubation probably lasts for about four weeks. Nothing seems to be 

 known about the young. 



Plumages. — So far as I know, no downy young, nestling, or young 

 juvenile zone-tailed hawks have ever found their way into collections, 

 and I have never seen any. I have, however, seen a number of imma- 

 ture birds taken in January, March, April, May, July, and Decem- 

 ber. These are evidently juvenal or first-year birds, and this plumage 

 is apparently worn without much change all through this year. The 

 contour plumage is much like that of the adult, but the concealed 

 portions of the feathers are more extensively white, and more or less 

 white spotting shows on the breast and back. The under sides of the 

 primaries are whiter than in adults, with narrower dusky bars; in 

 adults these are grayer, with more numerous and broader bars. The 

 tail is also quite diiferent ; on the upper side it is "fuscous" or "hair 

 brown", broadly barred with black and narrowly tipped with white ; 

 on the under side it is "pale neutral gray" and white, with a broad 

 subterminal bar and about half a dozen narrow bars of dark gray 

 or dusky. On the under side of the adult tail the three pure white 

 zones, on the inner webs of all but the central pair of feathers, are 

 very conspicuous against the otherwise black tail. Material is too 

 scanty to outline the molts. 



Food. — ^The zone-tailed hawk evidently feeds mainly on lizards, 

 frogs, and small fishes, which it finds along the beds of the streams 

 where it lives. It also eats a few small mammals and an occasional 

 bird. Harry S. Swarth (1920) shot at one which dropped a "desert 

 quail" it was carrying, and another had in its stomach the remains 

 of a Gila chipmunk. He writes : 



Although, as he circles about on lazy wings, or drifts slowly across a canyon, 

 the zonetail appears too sluggish for any rapid action, the capture of the chip- 



