332 HOMING WITH THE BIRDS 



to what vast height the birds can fly. Mr. ^Y. E. 

 D. Scott made a record on a night in October, 

 1880, in Princeton, New Jersey, of seeing through 

 an astronomical telescope large numbers of birds, 

 which crossed the face of the moon, flying between 

 one and two miles in height. Among these, he 

 positively identified warblers, finches, woodpeck- 

 ers, and blackbirds. Chapman made a record of 

 having counted three hundred birds in migration at 

 a height of between two and three miles. In my 

 own experience in a boat on the lake, w r ith an 

 unobstructed view on nights of very early spring, 

 I frequently hear the notes of flocks of small bird:; 

 passing over so high that I can not see them, but I 

 can recognize the voices; while I also know by my 

 own experience that on dark cloudy nights birds 

 in migration make twice the chatter and noise 

 that they do on a moonlight night. This probably 

 is to enable them to keep together, to let stragglers 

 know the position of the main flock. I frequently 

 hear them from my sleeping porch anywhere from 

 two to six o'clock in the morning. I think it a 

 well-established fact that the average flight of 

 birds in migration is at such a height that it is 

 ii f Icily impossible for them to see objects, which 

 could guide their course, and I know that this is 

 impossible on cloudy nights, when more birds 

 seem to be in migration than in fairer weather. It 

 is probable that the impression of numbers is ob- 

 tained by the birds' chattering, caused by the fact 



