Page:Natural History, Birds.djvu/36

Rh during the diminished light of the dusk or night. They have the head very large, with great, dilated, and projecting eyes, looking forwards, each surrounded by a concave disk formed of singular diverging feathers. Behind these disk-feathers is the opening of the ear, which in these birds is of immense size, and of elaborate construction. If we separate the feathers that form the hinder part of the disk, we shall expose the great ear enclosed between two valves of thin skin, from whose edges these feathers grow, and which are capable of being widely opened at the will of the bird, to catch every sound that may give notice of its prey amidst the silence and darkness. The plumage is lax and downy, a character that extends even to the wing-quills; whence the flight of the Owls is unattended with any sound produced by the striking of the air. Even the outer primary has the barbs of its edge separated like the teeth of a saw, allowing a passage to the air. The colours of the plumage are, for the most part, sombre, consisting of various tints of dull yellow, and brown, or white; often spotted, or minutely and most delicately pencilled: a peculiarity of coloration that we find in most nocturnal birds, and, by a beautiful analogy, in the moths and sphinges among Insects.

Mr. Yarrell observes, that from the loose and soft nature of the plumage in these birds, as well as their deficiency in muscle and bone, rapid flight is denied them as useless, if not dangerous, from the state of the atmosphere at the time they are destined to seek their food; but that they are recompensed for this loss, partly by their acute sense of hearing, from the structure of the ear