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* 
