“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.”

“See, here comes the moon up out of the water and it makes a shiny path up to our feet and Olaf is rowing back right down it and the stars have stopped winking and are getting dim,” said eager little Dodo, with an “and” wherever she ought to have stopped to breathe, as usual.  “Hark! the Herons are squawking again—­won’t you tell us about them now, Uncle Roy?”

A LONG-NECKED FAMILY

[Illustration:  Black-Crowned Night Heron.]

“The long-necked, long-legged, long-billed Heron family, to which these squawkers belong, contains many marsh-loving birds.  They are not exactly what we call shore birds, but live contentedly near any water, where they can wade and splash about pools and shallows for their food.  For they eat meat, though they never kill birds, like the cannibals.  Their taste is for frogs, lizards, snakes, snails, crabs, fish, and other small fry; they very seldom eat any warm-blooded animals.  Herons are all rather large birds, the smallest of them being over a foot in length, while the largest stand fully four feet high.”

“Quok!  Quok!” came the cry again, this time just over the cabin.  Looking up, the children saw a dark body flying toward the wood belt; something like a long beak stuck out from its breast in front, and its long legs were stretched out stiff behind, but these were the only details that they could distinguish.