“Oh, I remember that now,” said Nat.  “And after the young are hatched and the old birds need new coats, they keep rather still while they shed their feathers, because they feel weak and can’t fly well.”

“Then when the new feathers come they are sometimes quite different from the old ones, and seldom quite so bright—­why is this, Nat?” asked the Doctor.  But Nat could not think, and Rap answered:  “Because in the autumn when they make the long journeys the leaves are falling from the trees, and if they were very bright the cannibal birds would see them too quickly.”  “Have I told you about the Bluebird, and how, though he only sheds his feathers once a year, yet his winter coat is rusty and not bright clear blue as it is in spring?”

“I think not,” answered Nat.

“Well, the outside edges of its feathers are blue, but a little deeper in the feather is brownish.  So when they have worn the same feathers many months, and rubbed in and out of their little houses and bathed a great deal and cleaned their feathers off every day in the dust, as birds always do, the blue ends wear off and the rusty parts show.  It is quite worth while to tell little people things when they have the patience to listen and the interest to remember.”

“Yes, uncle, but it’s the way you tell us about birds that makes us remember.  You talk as if they were real people.”

“Oh, oh, Nat!” laughed the Doctor, “if you flatter me so I shall have to hide my head in a bush like an Ostrich.  Birds are people, though of another race from ours, and I am happy if I can make you think so.  Ah! we must be near a Redwing’s nest—­what a commotion the colony is making!”

“Colony?  I thought a colony was a lot of people who went off into a strange wild land and made a new home,” said Nat.

“That is one meaning of the word, but another one is when a number of people of the same race or trade live close to each other.  A bird colony is a collection of the homes of many birds of the same family.  After the nesting season almost all birds live in flocks of different sizes, each particular kind flocking by itself; but during the migrations great flocks are often made up of smaller flocks of various kinds of birds.  During the nesting season it is quite different; the majority of birds prefer a quiet home life, each pair being independent of any others.  Certain flocks, however, keep together, and all build their nests in a particular swamp or wood, and sometimes, it is said, male birds build nests to sleep in while the females are sitting.  The Redwings nest in colonies; so do the Herons, who eat frogs and nest near water, and the little brown-cloaked Bank Swallows, who live in holes that they dig for themselves in high banks.”

There were some twenty pairs of birds in this Redwing colony, who seemed to be much frightened by the approach of visitors.

“Here is a nest in this alder bush,” said the Doctor; “step carefully on the grass hummocks, and look at it for a moment, Nat.  See how neatly it is made of the dried leaves of flags and grasses, woven in and out between three upright stalks.”