Redbilled

Redbilled is a seldom-used, single-word variant of the more common hyphenated form red-billed. It functions as an English compound adjective indicating that something has a red bill (beak). In formal writing and standard style guides, the hyphenated red-billed is the preferred form; redbilled may appear only as a nonstandard spelling or in specific databases and informal texts.

The term appears most prominently in the common names of several bird species, where the color of the bill is a distinguishing field mark. Examples include the red-billed hornbill (Tockus erythrorhynchus), the red-billed quelea (Quelea quelea), the red-billed firefinch (Lagonosticta senegala), and the red-billed buffalo-weaver (Buphagus erythrorhynchus). These names help ornithologists and birders differentiate species with otherwise similar appearances.

In practice, the standard spelling in taxonomy and field guides is the hyphenated red-billed, as in red-billed hornbill or red-billed firefinch. The unhyphenated form redbilled is rarely used in authoritative contexts and is generally considered nonstandard. When writing about birds or discussing bill coloration more broadly, it is advisable to use the hyphenated form to avoid ambiguity.

See also beak coloration in birds, compounding in English, and lists of birds with color-based common names.