The speculum is a patch, often distinctly coloured, on the inner remiges of some birds.
Examples of the colour(s) of the speculum in a number of ducks are:
Common teal and green-winged teal: Iridescent green edged with buff.
Blue-winged teal: Iridescent green. The species' common name comes from the sky-blue wing coverts.
Crested duck and bronze-winged duck: Iridescent purple-bronze, edged white.
Pacific black duck: Iridescent green, edged light buff.
Mallard: Iridescent purple-blue with white edges.
American black duck: Iridescent violet bordered in black and may have a thin white trailing edge.
Northern pintail: Iridescent green in male and brown in female, both are white on trailing edge.
Gadwall: Both sexes have white inner secondaries.
Yellow-billed duck: Iridescent green or blue, bordered white.
Bright wing speculums are also known from a number of other birds; among them are several parrots from the genus Amazona with red or orange speculums, though in this case the colors are pigmentary and non-iridiscent.
