Much controversy has arisen concerning the noble Arctic Falcons (_Hierofalco_), especially those occupying Siberia and Northern America; it seems, however, most probable that three grey forms inhabit the latter and two the former region. In _H. candicans_, the Greenland Falcon, the prevailing colour is white at all ages, transversely marked above and spotted below with blackish; it occurs in North Greenland, Spitsbergen, Arctic Siberia and America, the Commander Islands, and Amur-land. _H. gyrfalco_, the Gyr- or Jer-Falcon[141] of Arctic America, Greenland, Scandinavia, Northern Russia, and possibly North Asia, is like a large Peregrine Falcon, but is greyer above and whiter below; _H. islandus_, the Iceland Falcon, of South Greenland, Iceland, North Siberia, and Arctic America is paler, having the whitish head streaked with dusky. _H. labradorus_, of Labrador, is dark throughout. All these species move southwards towards winter, the first three visiting Britain and the Greenland Falcon even Southern France. They are still valued in Falconry; but, though more powerful, they lack the spirit and dash of the Peregrine Falcon. The food consists of lemmings, grouse, sea-fowl, and the like; the nest of sticks, lined with softer materials, is placed on rocks or trees, and contains three or four whitish eggs mottled or completely covered with yellowish or cinnamon markings. Fam. V. PANDIONIDAE.–This group is especially remarkable for the reversible outer toe–recalling that of the Owls, the want of an aftershaft, and the long closely-feathered tibiae. The strong short beak is arched and decidedly hooked; the powerful feet are roughly scaled; the toes nearly equal, with no connecting membranes, but with spicules beneath; the claws sharp, curved, and rounded; the wings long; the tail comparatively short. The other structural details are as in the Falconidae. The downy young are dusky, varied with rufous; the lower breast, the abdomen, a central stripe down the back, and several on the head, being white.