170 PROBLEMS OF BIRD LIFE. 



case) birds of various species quickly collect, often in extraor- 

 dinary numbers. This pause allows the stragglers to come up, 

 and when the host again starts, the different leaders are natu- 

 rally followed by all the members of their own particular 

 species. I believe further that the southern extremity of the 

 Alleghanies is the chief point of departure in the eastern 

 United States. 



" It may be further objected that the adults of many or, as 

 I believe of all, species migrate southward first, and often 

 several weeks in advance of the young. It is perfectly true, 

 nevertheless, that a few old birds are always to be found in 

 the larger flights, although the latest of these are certainly 

 composed mainly of young. The two facts taken in connec- 

 tion, however, seem to me to strengthen rather than to weaken 

 the conclusions just advanced, for it is evident on the one hand 

 that many of the smaller parties must be entirely without ex- 

 perienced leaders, and equally clear on the other, that a few 

 such guides must always mingle in the armies which these 

 parties collectively form. 



"Another possible objection which has occurred to me is 

 that the flood-tide of migration is preceded, as well as closed, 

 by more or less local or limited movements, during which the 

 birds at any one time on the wing must be too few and too 

 scattered to constitute an uninterrupted stream. How, then, 

 do they find their way ? It may be answered that the earlier 

 flights can have no difficulty, for, as already stated, they are 

 made up chiefly, if not wholly, of old birds, who, being familiar 

 with the route, are independent. With the closing flights 

 there is more trouble, for these, as we have also seen, are com- 

 posed chiefly, and in) some cases entirely, of young. But is it 

 necessary to assume that such tardy travellers often reach 

 their southern destination, unless fortuitously and after long 



