Of all the classifications for chromaticity in the common names of birds, violaceous is certainly one of the most colorful. This word conjures images of the sultry Neotropics, where assorted trogons, euphonias, turacos, quail-doves, and jays parade about in their purple majesty. Violaceous is simply a fancy term for violet. Most of our violaceous avians are found in the New World, but there is a coucal, a type of ground-cuckoo, crawling around New Guinea that answers to that name.
Violaceous, derived from Violaceae, the name of the violet family of plants, possesses an undeniably ostentatious charm, but plenty of birds get by with the more vulgar violet. This descriptor applies most often to hummingbirds, or more specifically to their bellies, caps, chests, crowns, fronts, heads, tails, or throats.
Some regard violet as nothing more than a fancy term for purple, but in fact, the latter is subsumed by the former when it comes to the visible optical spectrum. Violet incorporates all the shades of purple from amethyst to wisteria. While wisteria isn’t employed in the characterization of avian coloring, amethyst makes a few appearances, again mostly among the hummingbirds, as do lilac and lavender. Purple enjoys an international, though somewhat indiscriminate popularity, used to describe hues as varied as the subtle wisteria (there, someone used this word!) of a Purple Sandpiper and the garish flamboyance of the Purple Gallinule.
The color described as violaceous or violet in birds is often more accurately classified as indigo, an extremely dark shade of violet. Ironically, when indigo appears in a bird’s name, it usually denotes a very vivid blue, as this Indigo Bunting indicates.