National Geographic : 1945 Jun
Sights and Sounds of the Winged World Study of Birds to Make NATIONAL GEOGRAPHIC Color Photographs Yields Rich Scientific Knowledge of Their Habits and Behavior By ARTHUR A. ALLEN Professor of Ornithology, Cornell University Lith Illustrations from Kodachromes by the Author MY PET crow, Jim, has given up the world of crows and prefers to live with me. Although he is free to fly off with his wild neighbors, they seem to hold no allure for him. "Hello, Jim," I say to him. He bows very politely, spreads his wings, wags his tail rap idly from side to side, and makes a rattling noise in his throat, a greeting I have never seen a wild crow give another. I did not teach Jim to do this; and since he was brought to me as a very young bird when his eyes were scarcely opened, I doubt that he learned it from his parents. I prefer to think of it as a spontaneous reaction devel oped through crow ages like a human smile. At the approach of my pointer or a stray cat, Jim stands high on his legs and hurls in vectives with wide-open mouth and vigorous shakes of his head. He sometimes scolds the wild crows that come into the trees near the house, though more often he pays no attention to them. The Same World Different to Man and Crow Jim's physical world and mine are fairly similar, but our reactions to parts of it are so different that I wonder whether he sees the same things I do, hears the same sounds, smells the same odors, and feels the same heat and cold. Surely, if things tasted the same to him he would not go after worms, grubs, and spiders with such avidity. He pays no attention when I talk to him in low tones, but if I whistle or squeak he shows instant alarm. Is he deaf to certain sounds and overrespon sive to others? How much of our world goes undetected by birds and how much of their world is be yond our ken? Some questions we may never answer, but others lend themselves readily to study and experimentation. Today it is comparatively simple to record accurately on film all the sounds made by birds * and then to analyze the visible sound track record and compute the exact changes in pitch of a bird's song. Indeed, the late Albert R. Brand, who started the bird-song recording project at Cornell, did exactly this for more than a hundred of our common birds. From his studies we know that the highest note of the blackpoll warbler is about 10,225 vibrations a second and the lowest note of the horned owl only 150. The average for some sixty songbirds is 4,280, or a quarter note higher than the highest note on the piano. An ingenious method of testing the hearing of birds, similar to that of the conditioned reflex developed by Ivan Petrovich Pavlov in his classical experiments on animals, was de vised by Mr. Brand and Paul Kellogg of the Cornell Laboratory of Ornithology. Giving some unexpected results, it helps to show how the bird's world differs from ours in at least one particular. Captive starlings, sparrows, and pigeons were trained to feed from a tray so wired that a slight shock could be given to their feet and at the same instant a note of known frequency sounded from an oscillator directly overhead. After a few repetitions of the sound-shock stimulus the birds would jump from the tray when the sound was given without the shock. When the birds were thus conditioned, the note from the oscillator could be raised or lowered until no response was forthcoming. What Birds Hear Through many repetitions of this experi ment it was learned that the range of hearing in starlings is from 700 to 15,000, that of the English sparrow from 675 to 11,500, and that of the pigeon from 200 to 7,500 cycles a sec ond. Man can hear about four octaves lower than the pigeon, or down to about 20 cycles a second, and most of us can hear the highest note detected by a starling. The sounds we hear extremely well, such as middle C on the piano, having a frequency of 259, would pass entirely unnoticed by spar rows and starlings, but are just within the hearing range of pigeons. When you talk * See, by Arthur A. Allen, "Hunting with a Micro phone the Voices of Vanishing Birds," NATIONAL GEO GRAPHIC MAGAZINE, June, 1937, and "Touring for Birds with Microphone and Color Cameras," June, 1944.