The term 'high-altitude nest' is often used to refer to an AERIE, which is a large nest built on a high cliff or mountain peak by birds of prey such as eagles and hawks. These nests are usually made of sticks and other materials found in the environment and can be quite large, sometimes reaching up to six feet in diameter. The purpose of these nests is to provide a safe place for the birds to raise their young, as they are often located in areas that are difficult for predators to reach.