BLACK GYRFALCON 13 



I have not seen any young of the black gyrfalcon in fresh juvenal 

 plumage. Except for generally darker colors, it is probably much like 

 the European bird of that age, of which Witherby's Handbook (1924) 

 says in part: "Upper mantle usually uniform dark brown, rest of 

 mantle and scapulars dark brown, feathers with brownish-white 

 edgings and spots; back, rump and upper tail-coverts with rather 

 larger spots and edgings, often forming bars on upper tail-coverts; 

 chin white, streaked dark brown; rest of under-parts very widely 

 streaked dark brown, feathers of flanks mostly dark brown with white 

 edgings and spots." 



Evidently the light-colored spots and edgings wear away during the 

 first fall and winter, for many immature birds in our series have uni- 

 formly dark brown upper parts. Some, or perhaps all, of these may 

 be more than a year old and may have partially molted their juvenal 

 plumage. This first, postjuvenal, molt is much prolonged, beginning 

 in summer, when the young bird is a year old, and continuing into the 

 following winter. Consequently there are many birds in collections 

 that are in this transition stage. All the immature specimens of 

 obsoletus that I have seen are heavily streaked on the under parts with 

 "clove brown" or brownish black, in many so heavily that the dark 

 color predominates. Air. Turner says that "birds of the year may be 

 distinguished by the color of the cere, tarsus, toes, and eyelids being 

 of a pale blue, while in the adults these portions are bright yellow at all 

 seasons." Young birds do not reach maturity in plumage until they 

 are nearly, or quite, 18 months old. 



In the normal adult plumage the crown, mantle, and wing coverts are 

 quite uniformly dark brown, "olive-brown" to "clove brown", some- 

 times interrupted by a few whitish streaks on the nape; the lower back, 

 rump, and upper tail coverts are grayer, or slaty plumbeous, but not 

 nearly so bluish gray as in the European birds; the upper breast is 

 heavily streaked, the belly heavily spotted with round spots, and the 

 flanks broadly barred with blackish brown or nearly black. In some 

 birds the entire body plumage, above and below, is nearly uniform, 

 dark, sooty brown, with little or no whitish anywhere; these are 

 probably melanistic individuals, or they may represent a dark phase. 



Ridgway (1880b) has described the adult plumage in detail. 

 Adults apparently have one complete annual molt between June and 

 January, though some of the primaries may be molted in spring. 



Food. — The food of this gyrfalcon is much the same as that of the 

 preceding race, with due allowance for the difference in habitat. 

 Mr. Turner says: "Their food consists almost exclusively of ptar- 

 migans, little else ever being found in their stomachs. They seize 

 their prey while on the wing, depending doubtless on their sudden 

 appearance among a flock of ptarmigans to put their prey to flight when 



