Gyrfalcon

Color plate showing a gyrfalcon as seen from the side, perched on a broken branch partly covered in snow. Its mate (presumably) can be seen a little farther behind. 

The gyrfalcon (Falco rusticolus) is the largest of all falcons. It is found in the northern hemisphere, where it breeds in the Arctic regions. Its color ranges from white, to brown, to black. The above illustration, made after Joseph wolf, shows the brown morph.