A nest is a place of refuge to hold an animal's eggs and/or provide a place to raise their offspring. They are usually made of some organic material such as twigs, grass, and leaves; or may simply be a depression in the ground, or a hole in a tree, rock or building. Human-made materials, such as string, plastic, cloth, hair or paper, may be used.
Generally each species has a distinctive style of nest. Nests can be found in many different habitats.
They may have some or all of the following zones: attachment; outer decorative layer; structural layer; lining.
Most species of birds build some sort of nest, though some lay their eggs directly onto rock ledges or bare soil without first modifying the area. Nest types vary from the very simple scrape, which is merely a shallow depression in soil or vegetation, to the elaborately woven pendant or sphere; some bird species use cavities in trees or dig burrows into the ground.