Humphrey–Parkes terminology

The Humphrey–Parkes terminology is a system of nomenclature used to describe the plumage of birds. Before this system, bird feathers were named based on if people thought they were used for breeding or not. This often led to mistakes. The Humphrey–Parkes system was made to fix these problems. It is named after P. S. Humphrey and K. C. Parkes.

Under this system, the main adult feathers of a bird, especially after a full change called a molt, is called basic plumage. In many birds, the feathers they wear when not breeding are basic plumage. For birds that change feathers only once a year, their adult feathers are also called basic plumage.

Some birds go through a smaller change of feathers, called a partial molt, before breeding. These special feathers are known as alternate plumage. If a bird has a third kind of feathers besides basic and alternate, it is called supplemental plumage. This is most common in ptarmigans. The first set of feathers a baby bird has is called juvenal or juvenile plumage.

While a bird is changing its feathers, the process is called a molt. Depending on which kind of feathers will follow, the molt can be called a prejuvenal, prebasic, prealternate, or presupplemental molt. For birds that do not become fully grown adults right away, numbers are used to show which set of feathers they are wearing. For example, the first time a bird gets its basic feathers, it is called first basic plumage. These numbers stop once the bird reaches its full adult feathers.