80 FOOD OF THE YOUNG 
But altricial birds which may be hatched at longer intervals are 
brooded more or less constantly for days or until their own feathers 
are sufficiently grown to protect them. Even then, when exposed to 
rain or sun, the parent may stand above them with half-spread 
wings. ; 
Food.—The young of precocial birds feed themselves, but either 
learn by experience or are taught by their parents what they shall eat. 
Recall a Hen clucking to her chicks and picking up and dropping bits 
of food she desires them to have. Even the act of drinking is not 
instinctive. (See especially Lloyd Morgan’s ‘Habit and Instincts.’’) 
The young of altricial birds, not only when they are in the nest, but 
as long as a month after leaving it, are fed by the parents. The nature 
of.the food and the manner in which it is given are subjects of far too 
great import to be adequately treated here. The food, at first, is usually 
more or less digested in the crop or stomach of the parent whence it is 
regurgitated into the mouth of the young. With Passerine birds, this 
method, when employed, is soon abandoned, and food in a more or 
less natural state is captured and given directly to the open-mouthed 
offspring; but the Flicker, Hummingbirds, and Doves, for example, 
feed only by regurgitation, inserting their bill far into the mouth of 
their young. . 
Young Pelicans, Cormorants, Water Turkeys, Spoonbills, and 
Tbises thrust their bill down the throat of their parents. Flamingoes 
introduce the tip of their great bill into that of their single chick, giving 
it, by regurgitation, a few drops of predigested liquid food, an exceptional 
method of feeding among precocial birds; young Herons grasp the bill 
of their parent at the base with their own, as one would with a pair 
of scissors, when the old bird either disgorges food into the nest or skill- 
fully into the mouth of the young. Hawks tear the food into bits 
and give it to their young, and larger insects are beaten or pulled 
apart by Passerine birds, both parents sometimes working together at 
the task. 
The young of Passerine birds are fed every few minutes throughout 
a greater part of the day, but the young of larger birds are waited on 
less frequently, hours often elapsing between meals, at which, however, 
they receive large portions. 
The rate of growth of young birds, particularly of young perching 
birds, is little short of marvelous. Herrick (’08, p. 187) writes of a 
young Cedar Waxwing the weight of which “doubled on the first day, 
more than trebled on the second, and nearly quadrupled on the third. 
On the twelfth day, when it weighed approximately one and one-fifth 
ounces, and had increased in weight thirteen-fold, it left the nest.” 
“At a corresponding rate of growth,” he adds, ‘‘a ten-pound baby when 
one day old would weigh twenty-one pounds, and at the age of twelve 
days one hundred and thirty-four pounds.” A young Song Sparrow, 
studied by Owen, weighed, on hatching, 2.9 grams, and when at the 
age of seven days it left the nest, 16 grams, (The Auk, 1899, p. 222.) 
