CASES OF ADAPTATION 143 



raillions each, we can partially realise the enormous quantity 

 of insect-food, required to rear perhaps five or ten times that 

 number of young birds from the egg up to full growth. Al- 

 most all of the young of the smaller birds, even when their 

 parents are seed-eaters, absolutely require soft insect-food, such 

 as caterpillars and grubs of various sorts, small worms, or such 

 perfect insects as small spiders, gnats, flies, etc., which alone 

 supjoly sufficient nourishment in a condensed and easily digest- 

 ible form. 



Many enthusiastic observers, by means of hiding-places near 

 the nests or by the use of field-glasses, have closely watched the 

 whole process of feeding young birds, for hours or even for 

 w^hole davs, and the results are extremelv instructive. The 

 chiff-chaff, for example, feeds its young on small grubs ex- 

 tracted from buds, small caterpillars, aphides, gnats, and small 

 flies of various kinds ; in a nest with five young, the hen-bird 

 fed them almost all day from early morning to sunset, bringing 

 mouthfuls of food at an average four times in five minutes. 

 This may no doubt be taken as typical of a number of the 

 smaller warblers and allied birds. 



Blue tits, with a larger family, worked continuously for 

 sixteen hours a day at midsummer, bringing about two thou- 

 sand caterpillars to the ravenous young birds, who, taking the 

 average at 10 (and they sometimes have 16) would swallow 

 200 each in the day. A pair of marsh tits were observed to 

 feed their young entirely with small green caterpillars, and 

 in one case made 475 journeys with food in seventeen hours. 



A gold-crest with eight young brought them food 16 times 

 in an hour for sixteen hours a day. A wren fed its young 

 278 times in a day. Even the common house-sparrow, itself 

 a typical seed-eater, feeds its young on caterpillars or on small 

 insects which it catches on the wins:. A flvcatcher was ob- 

 served to sit on a dead branch of an ash tree near her nest, 

 whence by short flights she cauglit small flies, etc., on the 

 wing, bringing a mouthful to her young every two to five min- 

 utes. 



