328 POPULAR SCIENCE MONTHLY. 



neighborhood and were seeking the proper elevation at which to con 

 tinue their flight, but after that time the line of flight was parallel to 

 the earth's surface.' He was able to identify positively only com- 

 paratively 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 ornithol- 

 ogists, 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 inter- 

 mittent 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. Fre- 

 quently, when few could be seen, hundreds were heard passing in the 

 darkness; the air was fllled with the lisping notes of warblers, and 

 the mellow whistle of tlirushes and at no time during the night was 

 there perfect silence." 



The latest recorded observations were made by Mr. 0. 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 esti- 

 mate the number of birds represented by these calls, but the effect was 

 impressive in the extreme. He says: "ISTothing but an actual experi- 

 ence of a similar nature can adequately convey the impression pro- 

 duced 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 cliinh 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. 



