. A dictionary of birds . the wing passes at first backwards, and then, becom-ing partially flexed with a whiplike action, it rises upwards, the, planeof the wing being .altered during the up stroke, so that it looksdown and forward. If the bird be flying fairly rapidly through theair, the up stroke is mainly a passive movement, the bird continuingto rest on the wings, and the velocity of the forward motion of itsbody diminishing, to be increased again Avith the next down starting, and before the bird has acquired velocity, the upstroke is an active one, and the primary feathers can
. A dictionary of birds . the wing passes at first backwards, and then, becom-ing partially flexed with a whiplike action, it rises upwards, the, planeof the wing being .altered during the up stroke, so that it looksdown and forward. If the bird be flying fairly rapidly through theair, the up stroke is mainly a passive movement, the bird continuingto rest on the wings, and the velocity of the forward motion of itsbody diminishing, to be increased again Avith the next down starting, and before the bird has acquired velocity, the upstroke is an active one, and the primary feathers can be provedto separate from one another, facilitating thereby the movementby reducing the resistance offered by the air to the back of theAving. The above description applies mainly to the Pigeon and Fio. 7. (From Marey.) FLIGHT 269 Gull, on which the observations have for the most part been made,but there is at present no reason for supposing that the activeflight of other birds differs from that described in any essential. Fig. 8.—Photographic trajectory of the tip of a Crows Wing. The little arrows shewthe direction of the tips movement. (From Marey.) particulars, though there is still a good deal to be learned about themechanics of active flight, and data sufficient, for example, to enableus to calculate the work done by a bird in flying through the airare still wanting. We have, hoAvever, in the above given only avery incomplete sketch of Avhat has already been learned on thesubject. III. We now come to the interesting subject of soaring or typical soaring birds come under Miillenhoffs ^ Vulture-type,whose sail-area in relation to the total weight of the bird is a largeone. In this category come such birds as the larger Corvidm, Eaven and Crow, the Falcons and Vultures, the Owls, Pelicans,and Storks. Those of them which can soar are mostly large birds,t\i a relatively large Aving-area, and few of them are commonlyvisible in this country, which is possib
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Keywords: ., bookauthorlyde, bookcentury1800, bookdecade1890, booksubjectbirds
