. Outlines of zoology. Zoology. FLIGHT. 617. Fig. 272.—Wings coming down.—From Marey. both directions are combined. The raising of the wing after each stroke requires relatively little effort, the resistance to be overcome being very slight. In steering, the feathers of the tail often bear to the wings a relation compar- able to that be- . ^iV&tfA^" tween rudder and sail. Modes of flight. —There are three chief modes of flight :— 1. By gliding or skimming, during which the bird has its wings spread, but does not flap them, depending for its movement on the velocity ac- quired by previ
. Outlines of zoology. Zoology. FLIGHT. 617. Fig. 272.—Wings coming down.—From Marey. both directions are combined. The raising of the wing after each stroke requires relatively little effort, the resistance to be overcome being very slight. In steering, the feathers of the tail often bear to the wings a relation compar- able to that be- . ^iV&tfA^" tween rudder and sail. Modes of flight. —There are three chief modes of flight :— 1. By gliding or skimming, during which the bird has its wings spread, but does not flap them, depending for its movement on the velocity ac- quired by previous strokes, by de- scending from a higher to a lower level, or by the wind. This may be readily observed in gull and heron, in a pigeon gliding from its loft to the ground, or in a falcon swooping upon its quarry. 2. By active strokes of the wings, in which the wings move down- ward and forward, back- ward and upward, in a complex curve. This is of course the commonest mode of flight. 3. By sailing or soaring with motionless spread wings, in which the bird does not necessarily lose in velocity, or in vertical position, as is the case in gliding. It is illustrated by such birds as crow, falcon, stork, and albat- ross, and has been ob- served only when there was wind. It is still imperfectly understood, but it probably depends on the varying velocity of the wind at different heights. The bird probably sails along the line of two currents of different velocity. Song1 of birds.—Singing is a natural expression of emotional. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, J. Arthur (John Arthur), 1861-1933. Edinburgh, Glasgow and London, H. Frowde and Hodder & Stoughton
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
