crissum
/ˈkrɪsəm/
noun
- The area of a bird's body around the vent (the opening for waste and eggs), including the undertail coverts.
- Ornithologists examine the crissum to tell similar-looking birds apart.
- The bird's crissum was white, which helped identify the species.
- The feathers on the crissum are often softer than those on the back.