"Quok! Quok!" cried a strange voice from the marshes back of the beach. "Quok, quok, quok, quok!" answered other voices.
"What can that be?" said Nat; "it isn't a Whip-poor-will, or a Nighthawk—it must be one of the cannibal birds. Uncle Roy, what kind of birds are those calling away over in the marshes?" But the Doctor was not within hearing, and it was some time before they found him, sitting by the cabin door smoking his pet outdoor pipe, which was made of a corn-cob.
"Did you hear the Night Herons calling as you came up?" he asked.
"We heard a very queer squawky sound, and came to ask you what it was, for we couldn't guess," said Nat. "What is a Night Heron—a cousin of the Nighthawk, who lives near the water?"
"I don't think it's a water bird," said Rap, "because I have heard that same squawking up by the mill."
"But is not the mill close to the pond?" said the Doctor, smiling.
"Why, yes, to be sure—but I was thinking of salt water."
"That is a distinction that applies to few of our water birds; when we speak of the birds that wade, paddle, swim, and dive, we must remember that they may do so in lakes, rivers, bays, or the ocean, according to their individual habits. In fact, some members of a single family prefer fresh water, while their brothers are more fond of the salt sea. This is the case in the family of the Night Heron."
"Where does he belong?" asked Rap, "with the paddling birds or the swimming ones?"
"With the paddlers and waders."