INTRODUCTION. 17 



even twitter, but at times some one of their number 

 will warble snatches of a summer-tide melody, and 

 the whole company applaud by a faint chirrupy twit- 

 ter that makes the hearer think of the far-off spring- 

 time of the coming year. Now the stay of the visitors 

 is very uncertain as to length : perhaps but for the 

 day, possibly for more than a week, and if we have 

 a long, dry, warm autumn, at least a fair proportion 

 may remain even longer. I am writing now of the 

 lower Delaware River Valley region, but the same 

 holds good elsewhere. It is well known that one 

 or more hardy species remain in New England all 

 winter, and so here a great deal depends upon the 

 weather and the food-supply as to when or how far 

 south they go. There are others of these warblers, 

 on the other hand, remarkably like many people we 

 meet, all method and without the power of novel 

 action. They go just so far north every May, and 

 proceed many miles farther south every autumn than 

 there is the slightest necessity for, if it is a matter of 

 food and warmth. They must do as their ancestors 

 did, and anything different is something to be de- 

 plored. It is different with some others of our birds. 

 They appear to be of an experimental frame of mind, 

 and it is now no uncommon sight to find overstaying 

 cat-birds, chewinks, thrushes, and a few summer spar- 

 rows that, as a rule, look up warmer quarters when 

 the river freezes. The water-birds, too, are disposed 

 to stay to some extent ; and herons, bitterns, and 

 rail-birds linger about the open spring-holes in the 

 marshes, and enliven many a stretch of nut-brown 

 meadow. But did those birds that come to us in 

 b 2* 



