The horneros are members of the genus Furnarius in the family Furnariidae, native to South America. Horneros are brown birds with rather short tails and fairly long bills. They are known for building mud nests that resemble old wood-fired ovens (the Spanish word "hornero" comes from horno, meaning "oven"). These nests have a unique chambered construction. While many Furnariids have different nests, the hornero nest is the reason for the common name applied to the entire family ovenbirds (though unrelated to the ovenbird, which is a parulid warbler). The size and exact shape of the hornero nest varies depending on the species. They generally lay two to four eggs, although the breeding behavior of the bay hornero is virtually unknown. Adult horneros can frequently be seen sitting on top of their nest. Disregarding the uncommon and relatively shy bay hornero, horneros are typically fairly common and highly conspicuous birds. They are generally noisy. All horneros are partially terrestrial, and commonly seen walking on the ground with a relatively upright posture.