WHITE GYRFALCON 5 



Eggs. — The white gyrfalcon lays ordinarily four or five eggs; these 

 are indistinguishable from those of the other races of the species, which 

 are described under obsoletus. The measurements of 90 eggs average 

 58.7 by 45.7 millimeters; the eggs showing the four extremes measure 

 64.4 by 50.8, 53.5 by 44.5, and 56.9 by 41.4 millimeters. 



Plumages. — I have never seen the downy young of this falcon and 

 doubt if there are any anywhere in American collections. This race 

 is easily recognized at any age, as it is always much whiter than any 

 of the other gyrfalcons. Dr. Koelz (1929) describes two nestlings, 

 which were still in the nest but fully feathered, as follows: 



The under parts are entirely white with a creamy cast, except for a band of 

 narrow streaking of brown on the feathers of the breast (the male specimen has 

 only the sides of the breast streaked), and broader streaks of the same color on 

 the feathers of the sides. The under tail coverts and the tarsals are immaculate. 

 The general tone is white above. The top and the sides of the head are faintly 

 lined along the feather shafts with dark brown. The feathers of the back have 

 a streak of brown along the shaft of the feathers, which broadens as it nears the 

 tip to become rather pendant shaped. On the shortest scapulars the drop becomes 

 broader so that the feathers here may be described as brown with a broad border 

 of white. The upper tail coverts are streaked like the breast. The tail feathers 

 are pure white. The wing coverts are marked about like the scapulars; the short 

 ones with a central field of brown and the longest ones with broken v-shaped 

 crossbars. The wing feathers are white with dark shafts and a few broken bands 

 of dark brown, chiefly near the tips. 



The two nestlings, described above, came from Etah in northern 

 Greenland. Of an adult candicans, also from northern Greenland, he 



The adult has the entire under parts immaculate. The back is chiefly white. 

 The crown, sides of head, and fore part of the back are unspotted except for a few 

 lines of black brown on the ear coverts and on a few feathers of the occiput. The 

 upper tail coverts, the rest of the back, and the wing coverts are barred with arrow- 

 shaped blotches of black brown. The tail is virtually pure white. The plumages 

 of adult and juvenile are thus different. Young birds have the markings paler, 

 probably more numerous, and they tend to run lengthwise of the feather, especially 

 on the short feathers. 



Specimens from farther south in Greenland, both juvenals and 

 adults, are darker, showing resemblances to corresponding plumages 

 of islandus, rusticolus, or even obsoletus. These are, of course, not 

 true candicans and have probably been produced by interbreeding 

 with the dark birds from Labrador. Hagerup (1891) says that 

 "Holboll and Fencker repeatedly observed mated pairs, one of which 

 was white (F. islandicus), and the other dark (F. rusticolus)" and that 

 "Holboll also found light and dark colored young in the same nest." 

 The latter is just what might be expected, as a result of the former, 

 under the well-known laws of heredity. 



The juvenal plumage is worn for a year or more and then gradually 

 molted between June and January. This new plumage is practically 



