National Geographic : 1932 Jul
SEEKING THE SMALLEST FEATHERED CREATURES Birds of this order are active at night, and, except for the nighthawks and their relatives, are not seen by day except when flushed from their roosting places. The name of goatsucker comes from a superstition of Old World peasants, who hear the calls of these nocturnal birds about their herds at night and believe that they subsist on stolen milk. Nightjar is a name bestowed in England, referring to calls heard from the woodland at night. The goatsuckers include about Ioo forms of small to medium size. All have soft, fluffy feathers, colored in delicate grays, buffs, and browns, with occasional markings of white. Their wings are long and pointed and their feet small, the claw on the middle toe possessing a comb, or pecten, perhaps of use in cleaning the plum age. The bill is small and weak, but the mouth is enormous, its capacious opening extending back beneath the large eyes. On opening the mouth, the outline of the lower portion of the eyeball is visible through the thin membranes lining the roof of the mouth. Years ago some nat uralists, believing that these birds had the power of rolling their eyes inward, so that they could look out through the transpar ent mouth membranes and so direct the capture of their insect food, aroused a highly amusing controversy that continued for some years before it was determined that the eye was really only slightly mov able in its socket. When at rest in trees, these curious birds ordinarily perch lengthwise on limbs, so that with their dull coloration they appear to be merely knots or excrescences. WEIRD VOICES HEARD ONLY AT NIGHT The voices of this family are unusual or even weird and, being heard mainly at night, have been the subject of much su perstition. Most of them consist of a rapid repetition of a phrase or a series of notes that may be heard for a considerable dis tance and in imitation of which many spe cies, as the whippoorwill, pauraque, and chuck-will's-widow, have been given their common names. Like many other nocturnal creatures, the eyes of goatsuckers shine from re flected light, and one method used in se curing specimens is to hunt them at night by the aid of headlights. While studying the bird life of the Chaco in western Paraguay, I went out one eve ning equipped with a small electric head light to ascertain the source of a tremulous call heard from the forest for several eve nings. The time was September, spring in the Southern Hemisphere, and the night air soft and warm, as I left the house. I walked slowly along a trail that led toward a deep forest. As I crossed an open pasture the eyes of horses glowed clear green in the reflection from my head light. A screamer called loudly from the edge of a lagoon, but flew with heavy flight without giving reflection of any kind from its eyes. In the trees were great beetles with two luminescent spots of clear green that shone steadily like little lamps, and I saw other small luminous points that I could not identify. The scent of blossoming trees hung heavy in the night air, and as I entered a footpath leading into the depths of a dense forest a jaguar coughed near at hand. My light threw only a small beam that illuminated a tiny circle of branches and leaves. The tremulous note that I had heard from the tree tops came now near at hand, and suddenly I saw a single spot of deep ruby red a few feet from the ground. The point seemed to be nearly an inch in diameter and appeared and disappeared, apparently as the bird turned its head. It suggested a glowing coal, but had a deeper, more intense light. Raising my gun so that the sight was visible in the weak ray from the headlight, I took careful aim and fired. In the dead night air the gas from the discharge crowded back in my face and the red spot disappeared. Hastening up, I found a beautiful little goatsucker (Setopagis par vulus), eight or nine inches long, of a kind that I had not seen before. The food of goatsuckers consists prin cipally of insects that the birds capture on the wing. They eat many moths, as these creatures are active at night, and also take almost anything else that flies. In the stomach of a wood nightjar (Nyctibius griseus abbotti) killed by Dr. W. L. Ab bott in Haiti were remains of beetles of very large size. The larger goatsuckers are known to swallow small warblers and other birds.