National Geographic magazine, volume 87, no. 6 (June 1945)

Page 112

726 The National Geographic Magazine beetles our birds have customarily fed upon. For that reason it has been virtually over­looked by them for several years. William R. Van Dersal lists 16 species of birds as having been observed eating the persimmon in the South, where it is native; yet in 25 years I have never seen a bird touch one of the fruits of a persimmon tree in my garden. My tree is, so far as I know, the only fruiting persimmon in this part of New York State, and consequently, though many of the birds Van Dersal lists pass through my grounds every fall and spring, it stands inviolate. Similarly the high-bush cranberry, relished by birds in New England, where it is native, is recommended by landscape gardeners else­where because "it holds its bright-red berries all winter and the birds don't bother it." I once fed a lot of cabbage worms to a young cedar waxwing I had rescued when it fell out of its nest. Apparently these caterpillars taken in large quantity are toxic to birds. They made the waxwing sick. After that experience he would not eat any kind of green caterpillar, though he readily took brown ones. Birds Use Touch in Choosing Food When I swept a hayfield with an insect net and dumped the contents before him, he at first sailed into the squirming, buzzing, crawl­ing, jumping mess of bugs and devoured them indiscriminately. He soon learned, however, to avoid the little bees and other stinging spe­cies, and to pass up all Hymenoptera and even the little tree hoppers with spines on their backs. Touch as well as taste and sight seems to enter into a bird's selection of food. Both scientists and laymen are still debating the problem of bird migration and the guiding principle that carries the travelers safely to their appointed summer and winter homes through clouds and storms, fog and darkness, without chart or compass. Is it possible, as many have suggested, that birds have a myste­rious sense of direction which enables them to utilize the magnetic lines of force on their long journeys?* Are birds mere automatons which receive stimuli and react mechanically, or are some of these stimuli cogitated and some of their actions controlled by an inner force? An albino rose-breasted grosbeak (Plate XVI) occupies a cage in my kitchen. Pur­sued by a hawk eight years ago, it flew into a window and stunned itself. It was at that time probably only a few months old, for conspicuous albinos usually do not last long in the wild. Though it has lived in our kitchen for eight years, it is still a wild bird. It has learned by long association not to fear us, yet it attacks my hand viciously when I clean the cage or offer it food. Through the window it watches the sky for hawks and the shrubbery for cats, and it is a veritable watchdog for notifying us in its own way when a predator is in sight. It has learned to get along without insects and has become overfat on a vegetarian diet, but it still behaves as a normal grosbeak. The Allen family has become a part of its habitat, to be accepted guardedly, but it bears toward us no affection or gratitude for solicitous care. Why should its behavior be so different from that of Jim Crow? A few years ago we were presented with a brown thrasher reared by Miss Edna Becker, one of my graduate students. A great pet, this bird had the run of the house. When we gave it entire freedom of the out-of-doors, it stayed in the shrubbery about the lawn and greeted all comers with friendliness, if a severe peck on the ankle or a tweak of the ear can be called friendly. Even our pointer received attention, a yank of the tail or the hair on his back. Quick as the dog was, he never quite caught Rufus. There was never any question that we were as much an integral part of the thrasher's life as we now are of Jim Crow's; yet when fall came, Rufus started wandering farther afield and then suddenly disappeared. Perhaps his friendliness toward human beings or his lack of fear of dogs got him into trouble, but I prefer to believe that the instinct to migrate, inherent in thrashers, stimulated him to take off south without understanding what was hap­pening. Effects of Early Training But why the difference in the behavior of the thrasher and the grosbeak-a difference that anyone who has ever kept wild birds in captivity has experienced? The grosbeak had passed at least the first month of its life in the wild, where the only part man played was that of an enemy. The thrasher, on the other hand, had been conditioned to man as a com­panion during this formative period. Two barred owls were brought to us six and ten years ago, respectively. One was a tiny downy youngster when he was found and the other nearly grown, though still with down on his plumage. To this day, though they have lived together for six years, their re­sponses to us are entirely different. The one we received very young flies to us; the other flies away. Throughout life birds re- * See "Bird Banding, the Telltale of Migratory Flight," by E. W. Nelson, NATIONAL GEOCRAPHIC MAGAZINE, January, 1928.