The little gold and olive mother, trusting Rap from past experience, gave a quick flip of her wings, and perched on a wild blackberry bush near by. The outside of the nest looked as if it were made of silvery-gray linen floss. There were some horsehairs woven in the lining, and here and there something that looked like sponge peeped out between the strands which held the nest firmly in the crotch of the elder stem.

"What is that soft stuff?" whispered Dodo.

"It is wool sc.r.a.ped from the stalks of young ferns," said the Doctor; "the soft brown wool that is wrapped round the leaves to keep them warm in their winter sleep until they stretch out of the ground and feel the warmth of the sun. The little Warblers gather it in their beaks and mat it into a sort of felt."

"There is something else in the nest-lining that looks like feathers,"

said Nat.

"That is dandelion down."

"Don't you think, Doctor, that this nest is very thick underneath?"

asked Rap. "It is twice as high as the one they built here last summer."

The Doctor felt of the bottom of the nest very gently with one finger and said, "I thought so! You have sharp eyes, Rap; it is very thick, and for a good reason--it is a two-storied nest!"

"A two-storied nest! Are there such things?" clamored the children together.

"The mother-bird is worrying; come over under the mulberry tree and I will tell you about this wonderful nest.

"There are some very ill-mannered shiftless Citizens in Birdland, called Cowbirds," began the Doctor; "you will learn about them when we come to the family to which they belong. They build no nests, but have the habit of laying their eggs in the nests of other birds, just as the equally bad-behaved Cuckoos do in Europe. Some birds do not seem to know the difference between these strange eggs and their own, and so let them remain until they are hatched. Others are wise enough to know their own eggs, and chief among such sharp-eyed ones is this little Yellow Warbler.

"Coming home some morning after taking exercise for the good of her health, Mrs. Warbler finds a great white egg spotted with brown, crowded in among her own small pale blue eggs, that have their brown spots mostly arranged like a wreath around the larger end.

"Being disgusted and very angry to find her house invaded, she and her mate have a talk about the matter. Why they do not simply push the strange egg out, we do not know, but instead of that they often fly off for milkweed fibres and silk to make a new nest right on top of the first one, shutting the hateful egg out of sight underneath. Then they begin housekeeping anew, in a two-storied nest like this one, living in the upper story, and keeping the Cowbird's egg locked up in the bas.e.m.e.nt, where no warmth from their bodies can reach it; and so it never hatches. If a second Cowbird's egg is laid, in the new upper story of the nest, the Warblers generally abandon their home in despair, and choose a new nesting place; but sometimes they build a third story over the other two, and thus defeat the evil designs of both their enemies without giving up their home.

"This nest of Rap's is a two-storied one, and when I touched the bottom I could feel that there was an egg in the lower story. By and by, when the birds have flown, we will take the nest apart and you can see for yourselves how ingeniously it is made."

"To think of all the ways birds have," said Rap; "going to such a heap of trouble for something they could fix with one good push."

"What happens when the Cowbird's egg stays in the nest and hatches out?

Aren't the other little birds squeezed and uncomfortable?" asked Dodo.

"Yes, they are very uncomfortable indeed, and often starve to death; but you must wait to hear about that until we come to the Cowbird himself."

"What family does he train with?" asked Nat.

"With the Blackbirds and Orioles," said the Doctor.

Then the male Yellow Warbler flew out along a branch above their heads, gave his lisping song, that sounded like "sweet, sweet, sweet, sweeter,"

seized an insect, and went across the garden toward his nest.

"I'm going to watch that nest," said Rap, "and if a Cowbird lays in it any more I'll take the wicked old egg away."

"Sweet, sweet, sweet," called the Warbler from the bushes.

"Maybe he understood you," said Dodo. "I'd believe most anything about birds."

The Yellow Warbler

(Or SUMMER YELLOWBIRD)

Length about five inches.

Upper parts rich olive-yellow, brightest on the rump and crown, but dark brown on wings and tail, with the inside half of each tail-feather yellow, and some yellow edgings on the wing-feathers.

Under parts bright yellow, in the male streaked with rich brownish-red.

A Summer Citizen of the greater part of North America, nesting in orchards and bushes, and going to the tropics in winter.

Belongs to the guilds of Tree Trappers and Sky Sweepers.

THE YELLOW-RUMPED WARBLER

(Or MYRTLEBIRD)

"This Warbler does not sing much of a song, even in nesting-time; but you will know him on the wing by the bright yellow spot on the rump, and if he perches near by perhaps you will also see the crown of gold on the head and a spot of yellow on each side of the breast. They say there was once a great king named Midas, whose touch turned everything to gold, he was such an avaricious old miser. If that be true he must have put his finger on the Myrtlebird in four different places. Unlike most of his family the Yellow-rump is fond of seeds and berries; and so he is able to live further north in winter than any of his brothers. Unless you are spending the summer near the Canadian border you will not see him in his own home. But when they are on their journeys in spring and autumn you will meet them almost everywhere, travelling in sociable flocks."

[Ill.u.s.tration: Yellow-Rumped Warbler.]

"It must be that dark-backed bird with a yellow spot on his tail, that gobbles all the bayberries--and eats the poison-ivy berries too," said Rap. "Yes, I see that you know him; 'that dark-backed bird with a yellow spot on his tail' is not a bad description of the Myrtle Warbler," said the Doctor; "at least, as you generally see it, in autumn or winter, when that particular spot is the only one of the four which shows off well."

"But why is he called _Myrtle_ Warbler?" asked Nat. "Does he build his nest in myrtle? I thought myrtle was that shiny-leaved plant down on the ground, that doesn't have berries."

"No, my boy, the bird is not named from that sort of creeping flowering myrtle; his name comes from a Latin word for 'bayberry,' because the bird feeds upon its fruit, as Rap told you."

"And bayberry is that low sweet-smelling shrub that we gather in the rocky pasture, to fill the great jar in the fireplace," said Olive.

"Some call it candle-berry, and others wax-myrtle."

"Yes," said Rap, "and these Warblers stay round that pasture in winter as long as there is a berry left."

The Yellow-rumped Warbler

(Or MYRTLEBIRD)

Length about five and a half inches

Upper parts dark gray, streaked with black; two white bars on each wing; large white spots on some of the tail-feathers. _A yellow patch on the rump and crown_.

Under parts white, streaked with black on the breast and sides. A yellow patch on each side of the breast.

A Summer Citizen of the northern United States and northward. Much less common in the West than the East. Travels south, and spends the winter everywhere from southern New England to Panama.

A great Seed Sower and a Tree Trapper.

THE OVENBIRD

[Ill.u.s.tration: The Ovenbird.]