A bird house is a structure designed to provide shelter and protection for birds. The most common type of bird house is the NEST, which is typically made from twigs and other natural materials. A CAGE is a more enclosed structure, usually made of metal or wire mesh, that provides a secure environment for birds. An AVIARY is a large enclosure, often made of netting, that allows birds to fly freely within it. A tree is a natural structure that can provide birds with a safe place to perch and NEST. Finally, a COTE is a small, enclosed structure, usually made of wood, that provides a safe and comfortable home for birds.