132 THE WORLD OF LIFE 



and that without them some of the most beautiful and 

 enjoyable of the living things around us would be either 

 seriously diminished in numbers or totally destroyed. He 

 might also be informed that he himself is a chief cause of 

 the very evil he complains of, because, by growing in large 

 quantities the plants the insect-pests feed upon he provides 

 for them a superabundance of food, and enables them to 

 increase much more rapidly than they would do under 

 natural conditions. 



Let us now consider what happens over our whole 

 country in each recurring spring. At that delightful season 

 our gardens and hedgerows, our orchards, woods, and copses 

 are thronged with feathered songsters, resident and migratory, 

 engaged every hour of the day in building their nests, 

 hatching their eggs, or feeding and guarding their helpless 

 offspring. A considerable proportion of these — thrushes, 

 warblers, tits, finches, and many others — are so prolific that 

 they have two or three, sometimes even more, families every 

 year, so that the young birds reared annually by each pair 

 varies from four or five up to ten or twenty, or even more. 



Now, when we consider that the parents of these, to the 

 number of perhaps fifty species or more, are all common 

 birds, which exist in our islands in numbers amounting to 

 many millions 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. Almost 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 supply sufficient nourishment 

 in a condensed and easily digestible 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 whole days, and the results are extremely 

 instructive. The chiff-chaff, for example, feeds its young 

 on small grubs extracted 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 



