Page:Popular Science Monthly Volume 60.djvu/336

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neighborhood and were seeking the proper elevation at which to continue their flight, but after that time the line of flight was parallel to the earth's surface.' He was able to identify positively only comparatively few species, such as the Carolina rail, grackle and a large snipe.

But perhaps the most satisfactory observations of all were those made also by Chapman, who, in company with a number of ornithologists, spent the night of September 26, 1891, at the Bartholdi Statue, New York. The weather proved to be exceptionably favorable, being clear during the early and later portions of the night, with an intermittent rain storm lasting for three hours between. As early as eight o'clock the birds began to be seen and heard, but almost simultaneously with the beginning of the rain there occurred a very marked increase in the number of birds seen about the light. They came singly, in troops, and in thousands, were visible for a moment and passed on into the darkness beyond. "The birds chirped and called incessantly. Frequently, when few could be seen, hundreds were heard passing in the darkness; the air was filled with the lisping notes of warblers, and the mellow whistle of thrushes and at no time during the night was there perfect silence."

The latest recorded observations were made by Mr. O. G. Libby ('Auk,' XVI., 140), who studied the nocturnal migrations at Madison, Wisconsin, in September, 1897. His first place of observation was a small elevation in the vicinity of three small lakes, where he undertook to make a record of the number of bird calls heard. During the night a total of 3,800 calls were recorded. The number of calls varied greatly, sometimes running as high as two or three per second and again falling to that number per minute. The largest number counted was 936.

From the nature of the data it was manifestly impossible to estimate the number of birds represented by these calls, but the effect was impressive in the extreme. He says: "Nothing but an actual experience of a similar nature can adequately convey the impression produced by such observations. The air seemed at times fairly alive with invisible birds as the calls rang out now faintly and far away, now sharply and near at hand. All varieties of bird calls came sounding out of the darkness that evening. The harsh squawk of a water bird would be followed by the musical chink of the bobolink. The fine, shrill notes of the smaller sparrows and warblers were heard only close at hand, but the louder ones came from all along the line, east and west. More than once an entire flock, distinct by the variety of their calls, came into range and passed out of hearing, keeping up their regular formation with the precision of a rapidly moving, but orderly body of horsemen. The great space of air above swarmed with life.