Owl weight varies among species but most adult owls weigh between 1.5 ounces and 9 pounds. Elf owls, the smallest owls in the world, reach a very short height and weigh much less than the largest owl breed, the Eurasian eagle owl. In the United States, common Barn owls range in weight from just 8 ounces to over 3 pounds, while larger snowy owls maintain adult weights of 3.5 to 6.5 pounds.
Many species of owls exhibit dimorphism, meaning adult males reach heights and weights exceeding those of females. Owls worldwide belong to two distinct families: strigidae and tytonidae. The strigidae family contains most owls, including nearly 190 species, while the tytonidae family includes approximately 16 species of barn owls. Adult owls from both families stand at full heights between 5 and 28 inches; fully-grown barn owls reach heights between 9 and 21 inches. Female owls lay between one and 14 eggs at a time. Most, however, hatch between two and six owlets, including female Eurasian eagle-owls. After hatching, young owls remain in their nests between 7 days and 6 months. Owls live and raise young in virtually every environment; most prefer deciduous habitats, although snowy owls prefer colder climates. Others, like burrowing owls, reside in deserts, and chestnut-backed owls make their homes in tropical rainforests.