As an antithesis to the apparently lifeless wings of the albatross, Pettigrew compares the ceaseless activity of those of the humming-bird. In these delicate and exquisitely beautiful birds, the wings, according to Gould, move so rapidly when the bird is poised before an object that it is impossible for the eye to follow each stroke, and a hazy circle of indistinctness on each side the bird is all that is perceptible. When a humming-bird flies in a horizontal direction, it occasionally proceeds with such velocity as altogether to elude observation. Mention of the calm majestic flight of the albatross suggests the possibility of birds resting on the wing. An American naturalist asserts that birds of prey and some others have the power to lock securely together those parts of the wing holding the extended feathers, and corresponding to the fingers of the human hand. The action of the air on the wing in this condition extends the elbow, which is prevented from opening too far by a cartilage, and the wings may keep this position for an indefinite length of time, with no muscular action whatever on the part of the bird. While resting in this way, the bird cannot rise in a still atmosphere; but if there be a horizontal current, it may allow itself to be carried along by it, with a slight tendency downward, and so gain a momentum by which, with a slight change of direction, it may rise to some extent, still without muscular action of the wings. This same naturalist also believes it quite possible for birds to sleep on the wing. As bearing on this subject, Professor J. S. Newbury asserts that he once shot a bird which came slowly to the ground as if still flying, but reached it dead. He believed that it had died high in the air; but had never been able to account for the manner of its descent till now, when he found an explanation in the statement just given.
Thousands of gold-crests annually cross and recross the North Sea at the wildest periods of the year, and unless the weather is rough generally make their migrations in safety. And yet this is the smallest and frailest British bird--a mere fluff of feathers, weighing only seventy grains. Another of the tits, the oxeye, has been met upon two occasions at six hundred and nine hundred miles from land. With regard to those birds which cross the Atlantic, it matters not for our purpose whether they are driven by stress of weather or cross voluntarily--suffice it they come. Less likely birds that have occurred in Britain are the belted kingfisher and American yellow-billed cuckoo. The white-winged crossbill must be mentioned with less certainty, for, although a North American bird, it is also found in some northern European countries.