[100] “If the albatross desires to turn to the right he bends his head and tail slightly upwards, at the same time raising his left side and wing, and lowering the right in proportion to the sharpness of the curve he wishes to make, the wings being kept quite rigid the whole time. To such an extent does he do this, that in sweeping round, his wings are often pointed in a direction nearly perpendicular to the sea; and this position of the wings, more or less inclined to the horizon, is seen always and only when the bird is turning.”--“On some of the Birds inhabiting the Southern Ocean.” Ibis, 2d series, vol. i. 1865, p. 227. [Illustration: FIG. 106.--The Pigeon (_Treron bicincta_, Jerdon), flying downwards and turning prior to alighting. The pigeon expands its tail both in ascending and descending.--_Original._] [Illustration: FIG. 107.--The Red-headed Pochard (_Fuligula ferina_, Linn.) in the act of dropping upon the water; the head and body being inclined upwards and forwards, the feet expanded, and the wings delivering vigorous short strokes in a downward and forward direction.--_Original._] _The Flight of Birds referable to Muscular Exertion and Weight._--The various movements involved in ascending, descending, wheeling, gliding, and progressing horizontally, are all the result of muscular power and weight, properly directed and acting upon appropriate surfaces--that apparent buoyancy in birds which we so highly esteem, arising not from superior lightness, but from their possessing that degree of solidity which enables them to subjugate the air,--weight and independent motion, _i.e._ motion associated with animal life, or what is equivalent thereto, being the two things indispensable in successful aërial progression. The weight in insects and birds is in great measure owing to their greatly developed muscular system, this being in that delicate state of tonicity which enables them to act through its instrumentality with marvellous dexterity and power, and to expend or reserve their energies, which they can do with the utmost exactitude, in their apparently interminable flights.