The Rufous Hornero (Furnarius rufus), often called the "ovenbird" of South America, is a fascinating and much-loved bird. Rufous Horneros are famous for building oven-shaped nests out of mud, straw, and manure. These nests harden like clay and can weigh up to 5 kilograms (11 pounds)! The nests are so well-built that they can withstand heavy rains, strong winds, and predators. Some abandoned nests even get reused by other birds, lizards, or small mammals. Mated Rufous Horneros often sing together