MEXICAN BL4CK HAWK 261 



northern Mexico and the United States, 3 consisted of three eggs, 6 

 of two, and 4 of one. Farther south the sets are apparently smaller, 

 for Mr. Thomas (1908) says: "According to several good authorities 

 the usual complement of eggs is two and three, but in only one in- 

 stance out of the twenty-seven nests examined was there more than 

 one egg, and this exceptional nest contained two. In some cases 

 they are beautifully marked with lavender, umber and light brown, 

 and in other cases they are totally unmarked ; however the greater 

 majority show distinct markings. * * * Like many other hawks, 

 if the nest is robbed, they at once go to work on another nest, and 

 I have taken three sets in one season from the same bird." 



The eggs that I have seen are ovate, short-ovate, or nearly oval. 

 The shell is finely granulated, and the ground color dull white. 

 They are sparingly spotted with dull or light browns, "sepia" to 

 "tawny-olive" or lighter; and some are nearly immaculate. The 

 measurements of 60 eggs average 57.3 by 44.9 millimeters; the eggs 

 showing the four extremes measure 66.5 by 44.5, 61.2 by 48.3, 50 by 

 45, and 53.1 by 42.3 millimeters. 



Plvmiages. — I have never seen the downy young, but Dr. Mearns 

 (1886) describes one, on which the feathers are just emerging, as 

 "Covered with dense woolly down, nearly white on head and breast, 

 passing into grayish posteriorly upon the head, throat, sides of 

 breast, tibiae, and back." On this bird the feathers appeared first 

 on the scapulars, wings, and tail, then on the body, as in other young 

 hawks. 



The Juvenal plumage of Unibifinga is quite distinctive, very dif- 

 ferent from any other North American hawk. The head, neck, and 

 entire under parts are from "cream-buff" to "cinnamon-buff" in 

 fresh plumage, heavily marked on the head and neck, nearly conceal- 

 ing the buff, less heavily on the belly and throat with elongated or 

 tear-shaped spots or streaks of brownish black; the tibiae are paler 

 buff, irregularly barred with dusky; the back, scapulars, and wing 

 coverts are brownish black or dark sepia, narrowly tipped, deeply 

 notched or barred with "tawny" or "russet"; the primaries are barred 

 on the outer webs with dark gray and black, the secondaries with 

 "fuscous" and black ; the under wing coverts are pale buff, sparingly 

 spotted, and the under side of the remiges is mainly whitish, irregu- 

 larly barred and broadly tipped with dusky; the tail is broadly 

 barred with black and white, four or five bars of each, tinged near 

 the end and on the under side with "pinkish buff" and some grayish. 

 As I have seen specimens in this plumage in every month in the 

 year, except January and May, it is evidently worn for at least the 

 first year without much change. A body molt begins in December, 

 at which more black plumage is acquired during winter ; the brown 

 edgings wear away and the buffs fade; the whole plumage becomes 



