INTRODUCTION. 23 



Buntings, and the much less common Evening Grosbeak and Bohemian 

 Waxwing. 



We may study the main features of migration to best advantage among 

 those species in which the whole body of individuals swings northward and 

 southward periodically and for long distances, at least 20° to 25° of latitude 

 or 1,200 to 1,500 miles. Among these are representatives of the most diverse 

 orders and families with many peculiar and exceptional cases, j^et much 

 general agreement as to the main facts. Some go openly, in immense flocks, 

 by day and in fair weather, as the swallows, sandpipers and crows; others, 

 like the cuckoos, flycatchers and rails, are commonly believed to go singly 

 and at night, and they drop away so stealthily, even mysteriously, that this 

 supposition seems justified. Many waterbirds, geese, ducks, and others, 

 seem to wait for storms of wind or rain and to delight in making their long 

 flights in or just before tempestuous weather. 



One of the older and seemingly well-grounded beliefs was that many of 

 the smaller and presumably weaker migrants travelled entirely at night, 

 partly to avoid the attacks of hawks and partly that they might rest and 

 feed by day. The fact that multitudes of such birds do travel at night is 

 undeniable, and perhaps the most marvelous demonstration of this is the 

 discovery (first announced in October, 1880, by W. E. D. Scott) that this 

 migration could be watched easily with a telescope trained on the face of the 

 full moon within a few hours of the horizon. Yet the fact seems to have 

 been very generally overlooked that night flying does not preclude day 

 flying, and that millions of small birds might pass over our heads at midday 

 and in fair weather, and yet be just as invisible as at midnight, provided they 

 flew at the heights claimed for the nocturnal migrants. Similarly, the fact 

 that birds appear by thousands about lighthouses and electric lights during 

 cloudy and foggy nights carries not the slightest proof that the same species 

 do not travel just as freely by day. As a matter of fact we know that almost 

 all the species killed at lighthouses do make long flights by day under favor- 

 able conditions, and an examination of all the accessible evidence leads me 

 to assert that most birds do not fly at night to avoid enemies or escape 

 observation, but merely to take advantage of favorable conditions as yet but 

 partially understood. Telescopic observations at night have shown many 

 small birds flying at heights of from one to three miles, and even at a height 

 of a mile most of the same birds would be entirely invisible to the unaided 

 eye in a clear sky at noon. Moreover, telescopic observations by day — the 

 telescope trained on the sun — have shown in at least two cases birds flying 

 at great heights, far above the reach of our unaided eyesight, and in one of 

 these cases the birds were migrating southward in enormous numbers. 



Different observers of nocturnal migration, using different instruments 

 under similar conditions (that is ahvays against the face of the full moon) 

 have recorded birds migrating at heights estimated all the way from 600 feet 

 to 15,100 feet, and moving at all speeds from nearly stationary up to 134 

 miles per hour, with an average of sixty-seven miles per hour for small birds 

 of ordinary powers of flight. 



I have not the least desire to belittle the discoveries of these pioneer 

 observers, or to cast any reflection on their honesty of purpose or the accuracy 

 of their records, yet I am free to say that until we have very many more 

 observations in corroboration of these I cannot but doubt that any of our 

 birds, large or small, at any height or under any circumstances, attains a 

 speed even approximating 100 miles an hour. At a height of little more 

 than three miles the density of the atmosphere is only half that at the sea- 



