The speculum is a patch, often distinctly coloured, on the secondary wing feathers, or 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-iridescent.
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