Some birds make their nests out of grass, twigs, and leaves. Others use mud, fur, or feathers. They might even use paper or yarn. Find out more in Bird Nests, a title in the Nature?s Engineers series. Nature?s Engineers is a series of AV2 media enhanced books. Each title in the series features easy-to-read text, stunning visuals, and a challenging educational activity. A unique book code printed on page 2 unlocksmultimedia content. These books come alive with video, audio, weblinks, slideshows, activities, hands-on experiments, and much more.