ly,
and not by an individual act of judgment. Instinct is not always
inerrant, though it makes fewer mistakes than reason does. The red
squirrel usually knows how to come at the meat in the butternut with
the least gnawing, but now and then he makes a mistake and strikes the
edge of the kernel, instead of the flat side. The cliff swallow will
stick her mud nest under the eaves of a barn where the boards are
planed so smooth that the nest sooner or later is bound to fall. She
seems to have no judgment in the matter. Her ancestors built upon the
face of high cliffs, where the mud adhered more firmly.

A wood thrush began a nest in one of my maples, as usual making the
foundation of dry leaves, bits of paper, and dry grass. After the
third day the site on the branch was bare, the wind having swept away
every vestige of the nest. As I passed beneath the tree I saw the
thrush standing where the nest had been, apparently in deep thought. A
few days afterward I looked again, and the nest was completed. The
bird had got ahead of the wind at last. The nesting-instinct had
triumphed over the weather.

Take the case of the little yellow warbler when the cowbird drops her
egg into its nest--does anything like a process of thought or
reflection pass in the bird's mind then? The warbler is much disturbed
when she discovers the strange egg, and her mate appears to share her
agitation. Then after a time, and after the two have apparently
considered the matter together, the mother bird proceeds to bury the
egg by building another nest on top of the old one. If another
cowbird's egg is dropped in this one, she will proceed to get rid of
this in the same way. This all looks very like reflection. But let us
consider the matter a moment. This thing between the cowbird and the
warbler has been going on for innumerable generations. The yellow
warbler seems to be the favorite host of this parasite, and something
like a special instinct may have grown up in the warbler with
reference to this strange egg. The bird reacts, as the psychologists
say, at sight of it, then she proceeds to dispose of it in the way
above described. _All yellow warblers act in the same manner_, which
is the way of instinct. Now if this procedure was the result of an
individual thought or calculation on the part of the birds, they would
not all do the same thing; different lines of conduct would be hit
upon. How much simpler and easier it would be to throw the egg
out