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National Geographic : 1947 Aug
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The National Geographic Magazine piazza already described, as well as a bird bath, two revolving feeders, and shrubbery planted especially to attract birds. Many visitors come to feast on the fruit of the cornel, lonicera, viburnum, and elder. Five scarlet tanagers were seen here at one time on the weeping mulberry tree; flocks of bluebirds and thrushes come for the woodbine berries; and partridges arrive regularly for cracked corn and the fruit of the bittersweet. Families of young are brought here for meals; foxes appear at the edge of the woods beyond; owls fly over, pursued by robins or other birds; and once the Websters saw a hawk being chased by two hummingbirds. A pileated woodpecker flies over frequently, and one year a pair of wood ducks passed by every afternoon on their way from their nest to the lake for feeding. Perhaps the most unusual occurrence was seeing and hearing a redpoll in full song-an exceedingly rare privilege so far south. Here, too, the hummingbirds are seen bathing. They usually take a "shower" in the rain, or in the spray from garden hose, but occasionally they "splash" vigorously on a rock wet with spray, or in a few drops of rain or dew in the depression of an upturned leaf. The latter makes an ideal bathtub for them. Evening Is Playtime Hummingbirds continue to feed until dusk, and during the peace and quiet of the evening show their greatest friendliness and fearless ness. Experiments tried at this time seem almost like games, which the birds apparently enjoy as much as the Websters do, for they flock around the upstairs window and allow many surprising "liberties." During this performance the family usually resorts to an insecticide, because bees, wasps, and mosquitoes also gather in large numbers. Curiously enough, the odor does not disturb the hummingbirds at all, but they are sensi tive to strange voices and will not come freely when a visitor is talking. It is interesting to observe the variation in pitch of the hum characteristic of the hum mingbird's flight. The pitch of extremely rapid flight, which is occasionally heard, is more than an octave higher than the lowest hovering note. In the spring, as the day for the birds' return approaches, everything is in readiness to provide their special refreshment. On their arrival they fly directly to the position where each bottle was located the previous year, then watch as the bottles are filled and put out, as if there had been no interruption in their visits. This has happened so many times that no banding is necessary to prove the same birds return year after year. These birds have become so accustomed to being studied at close range by large groups of people that they were only temporarily disturbed by the assembling of my photo graphic equipment. The series of Kodachromes reproduced with this article was made last summer with both 2/" x 3/" and 4" x 5" cameras, with two Kodatron electric-flash lamps spaced about two and one-half feet from the subject. A CC15 filter was used to correct the color of the light to give true rendition. An aperture of f:8 was used. Kodachromes were also made with an ex perimental flash unit some ten times more powerful than the Kodatron. Most of the birds would fly a few feet away after the flash of light, but invariably they returned immediately to continue their repast. Eventually some of the birds ignored the lights, even when the larger flash units were concentrated only a few feet away to obtain sufficient illumination for color photography at f:16. High-speed motion pictures were also taken of the birds with a stroboscopic lamp synchro nized to the motion of a continuously moving film. This camera was operated at 800 frames per second with an exposure time of 0.00001 second per picture. Camera Whir Disturbed Birds The sirenlike noise of the camera running at this speed seemed to disturb the birds, so the camera was put in the house and the movies taken through the window. A shield was constructed to obscure the direct daylight from the camera; otherwise it would have produced a blur on the film. A collection of motion pictures was taken which showed the birds in several phases of flight, landing, and take-off. Many people have enjoyed these pictures on the screen, since the motion of the wings can be slowed down until it is possible to see what is hap pening. A study of the film shows that the wings beat 55 times per second on the average when the bird is hovering. The wing-tip ve locity is about 29 feet per second (20 miles per hour). With an exposure of 1/3000 second, as is used in the color pictures, the wing tip shows about a 1/10-inch blur because of the motion. 224
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