22 THE BIRDS OF NEW JERSEY. 



their food over wide areas. Hence, like Swallows, Swifts 

 and Hawks, they migrate during the hours of their habit- 

 ual activity." 



Day migrants perform their journeys either as scatter- 

 ed individuals, or in compact flocks, there being compar- 

 atively little mixture of species. As regards night mi- 

 grants, however, the case is different. All the species 

 which are migrating on any particular night, being 

 attracted by each others' notes, become more or less 

 mingled together in an immense column, not forming a 

 compact flock, but composed of individuals and small 

 bunches flying sufficiently near to one another to be guid- 

 ed by the chirping of those just ahead. Observations 

 made from lighthouses seem clearly to show this to be the 

 nature of the night migrations, and it is really most nat- 

 ural, being merely a continuation of the actions of these 

 same birds while feeding in the woodland during the day, 

 when they go shifting from tree to tree, the various 

 species intermingled and all slowly following the lead of 

 those just ahead of them. The leaders of these migra- 

 tory flights are probably old birds which have had the 

 experience of previous migrations and have thoroughly 

 learned the route of travel. The experience of most of 

 the leading ornithologists of this country, however, seems 

 to show that the old birds of most if not all species mi- 

 grate southward before their young, leaving the nesting- 

 ground soon after the moult is completed and entrusting 

 their young to the guidance of later migrants, often be- 

 longing to quite different species. 



Migrating birds seem to follow the same course year 

 after year, so that it is possible to map out pretty exactly 

 their principal lines of flight. These lines of flight fol- 

 low the courses of rivers, valleys, mountain chains, or 

 coast lines, which to the eyes of the migrants, flying high 

 in the air, are distinctly outlined for many miles, pro- 

 vided the night be clear, and thus form easily recogniz- 

 able landmarks. 



