MIGRATION 95 



Although the migratory movements such as we have just 

 described take place, as a rule, on a stupendous scale they attract 

 comparatively little attention. A few stragglers tell us that 

 the arrival of our guests is at hand, or remind us that they have 

 departed, but the main body of these wandering hordes is seen 

 but by a few privileged ones. And this largely because, as a 

 rule, they come in rushes, and come, very commonly, by night, 

 leaving in a like manner. This, however, is largely determined 

 by the conditions of the weather. But whether they travel by 

 day or night, as a rule they appear to prefer to perform their 

 journeys at high altitudes, perhaps because less wearisome. 

 Often they betray their presence only by their whistling, though 

 it would appear that as a rule they travel in silence, save only 

 on dark, foggy nights, when their constant cries serve to keep 

 the troop together. 



American naturalists have made some interesting observa- 

 tions by directing a telescope against the sky. Thus Mr. Frank 

 Chapman, by turning his instrument towards the full moon, has 

 seen birds passing at night at an altitude, according to his 

 computation, of five miles, while Mr. W. E. D. Scott saw, 

 through an astronomical telescope at Princeton, in New Jersey, 

 great numbers of birds passing across the face of the moon. 

 Most of these were the smaller land birds, among which he 

 recognised Warblers, Finches, Woodpeckers and Icteridje 

 {Quiscalus purpureus). These, it is computed, were travelling 

 at heights varying from one to two miles. Mr. Chapman again, 

 on another occasion, when in New Jersey, during three hours 

 saw no less than 262 birds pass over the field of the telescope 

 at a height of from 1,500 to 15,100 feet ; and the most remark- 

 able thing of all was the fact that the lowest birds were flying 

 upward, as if they had risen from the immediate neighbour- 

 hood and were seeking the proper elevation at which to continue 

 their flight. Mr. S. Tennant has recorded the fact that through 

 a telescope turned towards the sun, at Roorkee, he saw birds, 

 apparently Kites, frequently pass over its face, some of which 

 were in focus with the sun itself and must therefore have been 

 several miles high, while the nearest must have been quite a 

 mile above the earth's surface. These birds, it should be re- 

 marked, were soaring in search of prey, and not migrating. 



More than once doubt has been expressed as to whether 



