The Zoologist — November, 1871. 2819 



their birth. They are, no doubt, driven away by their parents, as is 

 commonly the habit of birds of prey, and follow the large flocks of water- 

 fowl, which are bred in the north, on their southward migration, though it 

 would appear that the ptarmigan forms the chief sustenance of the old 

 birds. At the same time, it must not be supposed that in Greenland the 

 white form only is found. In the southern districts of that country the 

 Iceland falcon is certainly more numerous, and, on the other hand, there is 

 good reason for believing that the Greenland falcon bi'eeds in some of the 

 northern parts of British America, and perhaps even in the Old World." — 

 Page 36. 



The Iceland Falcon. — " The chief differences between the subject of the 

 preceding article and the Iceland falcon have therein been succinctly 

 mentioned. It remains to point out the characters which distinguish the 

 latter from the true gyr-falcon of the Scandinavian Peninsula, and probably 

 of countries further to the eastward. In immature plumage the two birds 

 greatly resemble each other, so much so that it is often not easy at first 

 sight to separate them, especially as the Icelander, like the Greenland 

 falcon is subject to a considerable amount of variety in the prevailing shade 

 of tint, and it is quite possible that examples of the true gyr-falcon have 

 occurred in these islands, and have been mistaken for the common form. 

 As a rule, however, it may be asserted that in the Iceland falcon the crown 

 of the head is lighter, and generally much lighter, in colour than the back, 

 while in the gyr-falcon the crown of the head and the back are of the same 

 hue, or the former is darker. In the gyr-falcon, also, there is commonly a 

 very perceptible black mystacial streak or patch, which in adults of this 

 form is often as much developed as we find it in the common or peregrine 

 falcon, and the coloration generally is darker than in the Icelander. The 

 late Mr. Hoy, who was well versed in falconry, and seems to have been the 

 first English writer to clearly distinguish the two forms, has pointed out 

 (Mag. Nat. Hist. vi. p. 108) some other differences. The Icelander, he 

 says, rather exceeds the gyr-falcon of Norway in size ; the tail is considerably 

 shorter ; the wings are in proportion longer, and the head is larger, so much 

 so that, in modelhng the hoods for trained birds of the two kinds, falconers 

 use different blocks. Whether all these distinctive features can be esta- 

 bhshed on the comparison of a large series of specimens is perhaps 

 uncertain, but it does appear that in some parts at least of the structure of 

 the two forms there exists a remarkable difference of proportion, which 

 does not seem to have been hitherto noticed. The average length of the 

 sternum and coracoid in Falco islandus, as ascei;taiued by the careful 

 measurement of six female specimens, not specially selected for the pur- 

 pose, in the Museum of the University of Cambridge, is 5.46861 in., while 

 the average length of the same bones in as many specimens of F. gyrfalco 



