The nostril covering found in pigeons and doves, it is protected or partly covered by a swollen opercula, a cover of skin that leaves only a narrow slit for the passage of air [1].
References[]
^Terres, John K. (1980). The Audubon Society Encyclopedia of North American Birds. Alfred A. Knopf, Inc. ISBN0394466519.
This article is part of Project Glossary, an All Birds project that aims to write comprehensive articles on each term related to animals.