The second plumage of a bird that takes more than one year to obtain adult plumage (e.g. eagles). Usually but not always acquired at one year of age and usually worn for a year. It is followed by Basic II, Basic II, etc. .
|This article is part of Project Glossary, a All Birds project that aims to write comprehensive articles on each term related to animals.|
|This article is part of Project Anatomy, a All Birds project that aims to write comprehensive articles on each anatomical term related to birds.|
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