. Animal flight; a record of observation . In addition there maybe movements or adjustments for checking speed in-dependently of those used for perching. It is necessary to find a simple form of flight inwhich the propulsive movement may be studied desideratum is supplied in a very satisfactory wayby the poising of the pied kingfisher in calm air. The pied kingfisher (Ceryle rudis) differs from otherspecies of kingfisher in having a habit of poising in theair and then suddenly diving down head foremost onto its prey. While poising the bird appears as if fixedin one position with its
. Animal flight; a record of observation . In addition there maybe movements or adjustments for checking speed in-dependently of those used for perching. It is necessary to find a simple form of flight inwhich the propulsive movement may be studied desideratum is supplied in a very satisfactory wayby the poising of the pied kingfisher in calm air. The pied kingfisher (Ceryle rudis) differs from otherspecies of kingfisher in having a habit of poising in theair and then suddenly diving down head foremost onto its prey. While poising the bird appears as if fixedin one position with its wings in rapid motion. It mayremain thus poised for several seconds at a time. The following measurements were obtained from aspecimen of this bird : Weight 90 grammes, say 3 ozs. Span i8in. Length n^in. Area of wings . .352 sq. It,Loading . . .76 lb. In the case of the pied kingfisher poising in still air,since the wings are propelling it vertically upwards, thepropelling movement has no admixture with any other ANIMAL FLIGHT. lS3. Fig. 36. Pied kingfisher poising at com-mencement of down-stroke. movement or disposition for counteracting there are no directive movements as the bird isnot travelling from place to place. If a pied kingfisher is watchedunder these conditions it will beseen that the movement of thewings is not up and down butto and fro in a perfectly hori-zontal direction. It will be con-venient however to use the termup-stroke and down-strokein describing the movement ofits 36 shows the position ofthe wing at the commencementof the down-stroke. Fig. 37 showsthe position at the end of thedown-stroke. During the down-stroke, asshown in fig. 38, the Wing IS Pied kingfisher poising atmoving horizontally forwards. end of down-stroke-The quill feathers, by the pressure of the air, are bent backwards. The area of the wingtherefore forms a slanting surface. Thepressure of the air on this slanting sur-face results in a component tending tolift the
Size: 1714px × 1457px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectan, booksubjectflight
