64 NATURE STUDY. 



were or might be rivals. Presently a female appeared and 

 slowly approached one of them, but he did not change his 

 position or alter his note. Not until she had mutely and 

 patiently stroked him with her slender antennae did he 

 give her the slightest notice, or appear to be conscious 

 that there was or could be any one but himself in the 

 world. 



The most weirdly fascinating of all night sounds is the 

 call note of the song birds in their fall migration. It comes 

 from out the darkness — sometimes anxious and inquiring, 

 sometimes calm and reassuring, repeated again and again 

 as the birds pass swiftly onward, until the imagination 

 runs riot and the night air seems filled with an invisible 

 multitude. In truth, the number must at times be great, 

 for the calls are frequent, and it is not possible that nearly 

 all cry out within range of our hearing, while no bird could 

 be heard more than once by the same listener in its rapid 

 flight. 



The long, mysterious procession of the birds begins as 

 early as the middle of August in northern New England: 

 The bobolinks and the swallows start off first, impatient 

 for the more abundant food of the southland. They are 

 followed by a swelling throng, the number of migrants 

 increasing until along in October, when it decreases until 

 November and the bluebirds and the robins bring the mi- 

 gration to an end. Instinct, very likely acquired through 

 bitter experience of ancestors long ago, impels the song 

 birds to make their journey in the night. The hawks and 

 kites are then at rest ; the owl swoops downward only from 

 some perch to seize his prey, and is in no way fitted to 

 seek his victims overhead. The great highways of the air 

 are therefore free from marauders, and the tiniest songster 

 passes swiftly and safely on its course, protected by the 

 darkness. 



As is well known, the song birds, when the task of rear- 



