142
Concord, Mass.
1898.
June 22
  Forenoon clear and sparkling with cool east wind.
A heavy thunder shower in the afternoon.
  Walking around Ball's Hill immediately after breakfast
I heard, besides many of our common summer birds, a
Canadian Warbler and a Solitary Vireo. The Warbler was
singing near the crest of the ridge behind the cabin.
It had probably come from Davis's Swamp where I 
heard one singing about two weeks ago, although it is
just possible that it may be mating in the Ball's Hill
Swamp (an old breeding station) and by some chance
may have escaped my attention up to this time.
  The White Maples along the river banks are infested
with grass-green caterpillars which are fast denuding these
beautiful trees of their foliage. Not content with eating
what they require the caterpillars bite off pieces of the leaves one
or two inches square. The ground under the trees
and the surface of the river as well are strewn
thickly with these fragments. Having constantly seen or
heard Cuckoos (of both species but oftenest the Yellow-Bills)
of late in the maples over the canoe landing I watched one
of the birds (C. americanus) closely today and found, as I had
suspected, that it was feasting on the caterpillars.
It obtained them by flitting or hopping from branch
to branch and reaching or fluttering up to sever them 
from the under sides of the leaves. I saw it catch
and devour six within the space of as many
minutes. I doubt if we have any bird that is much
more valuable as a guardian of our shade trees than
Cuckoos.