thumb|right|300px|A male [[mallard. The speculum feathers are bright blue with white edges]]
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. 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.
- American black duck: Iridescent violet bordered in black and may have a thin white trailing edge.
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.