5o6 THE POPULAR SCIENCE MONTHLY, 



THE NOCTURNAL MIGRATION OF BIRDS. 



Br FEANK M. CHAPMAN. 



"'VTO braucli of ornithology offers more attractions to tlie stu- 

 -L> dent of birds than the fascinating subject of migration. 

 Birds come and go; absent to-day, to-morrow tliey -greet us from 

 every tree and hedgerow. Their departure and arrival are gov- 

 erned by as yet unknown laws; their journeys through the path- 

 less sky are directed by an instinct or reason which enables them 

 to travel thousands of miles to a winter home, and in the spring 

 to return to the nest of the preceding year. 



Volumes have been written to explain their mysterious appear- 

 ances and disappearances. 



Theories almost as numerous as the essays themselves have 

 been advanced to account for the phenomena of migration. 

 From the time of Jeremiah (viii, 7) to the present day we might 

 cite a host of authors who have contributed to the literature of 

 the subject. It is not our intention, however, to review the 

 whole question of migration. The combined researches of orni- 

 thologists have placed it among the sciences, and its more promi- 

 nent facts are common knowledge. We desire here to call atten- 

 tion to but one phase of the study, and more especially to outline 

 some recent investigations in connection with the nocturnal mi- 

 grations of birds. 



From the nature of the case, our data concerning these night 

 flights have long been meager and unsatisfactory. Even now 

 our information has but reached a stage which permits us to in- 

 telligently direct further effort. 



We know that the land birds which migrate by night include 

 species of more or less retiring disposition, whose comparatively 

 limited powers of flight would render them easy victims for birds 

 of prey if they ventured far from the protection of their natural 

 haunts during the day. Thus we find that the bush- or tree-lov- 

 ing thrushes, wrens, warblers, and vireos all choose the night as 

 the most advantageous time in which to make their long semi- 

 annual pilgrimage, while such bold rovers as swallows, swifts, 

 and hawks migrate exclusively by day. 



The information we possess concerning the manner in which 

 the first-mentioned class of birds accomplish a journey which 

 leads them from boreal regions to the tropics, has been derived 

 from three sources : First, through the birds which are killed by 

 striking lighthouses or electric-light towers ; second, through 

 observations made at night from similar structures; and, third, 

 through the use of the telescope. 



It has long been known that lighthouses are most destructive 



