"Trees! Yes, trees of course," cried the children eagerly; "all kinds of trees, for trees grow apples and pears and plums and cherries and chestnuts and firewood too." "Now what is there that preys upon all this vegetable life--upon every plant, from the grass to the tree, destroying them all equally?" "Bugs and worms and all kinds of crawlers and flyers and hoppers," said Rap. "Yes, every plant has an insect enemy which feeds upon its life juices. So a set of animals has been developed by Heart of Nature to hold the plant destroyers in check, and these animals are the birds. "Man may do all he can to protect his gardens, his orchards, his fields and forests, but if the birds did not help him the insects that work by night and day--tapping at the root, boring inside the bark, piercing the very heart of the plant, chewing off the under side of leaves, nipping off the buds--would make the earth bare and brown instead of green and blooming. Yet House People, both young and old, forget this. They shoot and frighten away the birds, either because some few of their feathered friends take grapes or other fruits and berries by way of pay, or merely from thoughtlessness, to see how many they can hit." "Do _all_ birds eat bugs and such things?" asked Nat. "Olive said she used to put out grain and crumbs in winter for some kinds." "Some birds eat animal food and some seed food, while others eat both; but almost all birds feed their babies upon insects. The nesting season is chiefly in spring, when all plants begin or renew their growth. Spring is also the season when the eggs of many insects hatch out and when others come from the cocoons in which they have slept all winter. "Then the farmer begins his annual war upon them, and day after day he fights the Battle of the Bugs. But if he stops to think, and remembers that Heart of Nature has a use for everything, he will win this battle against the creeping, crawling, squirming regiments more easily. For above him in the trees of his forest, in the hedgerows and bushes of his pasture and garden, on the rafters of his barn, even in the chimney of his house, live the birds, willing and eager to help him. And all the wages they ask is permission to work for a living and protection from those of his fellowmen who covet the Oriole and Cardinal for their gay feathers and the Robin and Meadowlark for pot-pie." "Singing-bird pie is wicked. I would like to pound them all," said Dodo, striking her fists together, as Nat did sometimes, not making it clear whether it was pie or people she wanted to pound. "But uncle, it is right to eat some birds--Ducks and Chickens and Geese and Turkeys."