Elf owls, barely four inches tall, eat insects and live in abandoned woodpeckers’ nests in giant cacti in the southwestern United States and Mexico. African pygmy falcons are so small that they can live inside the many-chambered nests of sparrow-like songbirds called sociable weavers, and leap out from time to time to feast on their neighbors. A diminutive falconet from the Philippines is smaller than the largest hummingbird.
