yellow corn scattered.

Blacky wasn't wholly surprised to find Dusky the Black Duck, own
cousin to Mr. and Mrs. Quack the Mallard Ducks, with a number of his
relatives in among the rushes and wild rice at the very place where
that corn had been scattered. They seemed quite contented and in the
best of spirits. Blacky guessed why. Not a single grain of that
yellow corn could Blacky see. He knew the ways of Dusky and his
relatives. He knew that they must have come in there just at dusk
the night before and at once had found that corn. He knew that they
would remain hiding there until frightened out, and that then they
would spend the day in some little pond where they would not be
likely to be disturbed or where at least no danger could approach
them without being seen in plenty of time. There they would rest all
day, and when the Black Shadows came creeping out from the Purple
Hills, they would return to that place on the Big River to feed, for
that is the time when they like best to hunt for their food.

Dusky looked up as Blacky flew over him, but Blacky said nothing,
and Dusky said nothing. But if Blacky didn't use his tongue, he did
use his eyes. He saw just on the edge of the shore what looked like
a lot of small bushes growing close together on the very edge of the
water. Mixed in with them were a lot of the brown rushes. They
looked very harmless and innocent. But Blacky knew every foot of
that shore along the Big River, and he knew that those bushes hadn't
been there during the summer. He knew that they hadn't grown there.

He flew directly over them. Just back of them were a couple of
logs. Those logs hadn't been there when he passed that way a few
days before. He was sure of it.