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.[1]
- Blue-winged teal: Iridescent green.[2] The species' common name comes from the sky-blue wing coverts.
- Crested duck and bronze-winged duck: Iridescent purple-bronze, edged white.[3]
- Pacific black duck: Iridescent green, edged light buff.[3]
- Mallard: Iridescent purple-blue with white edges.[1]
- American black duck: Iridescent violet bordered in black and may have a thin white trailing edge.[1]
- Northern pintail: Iridescent green in male and brown in female, both are white on trailing edge.[2]
- Gadwall: Both sexes have white inner secondaries.[1]
- Yellow-billed duck: Iridescent green or blue, bordered white.[4]
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,[5] though in this case the colors are pigmentary and non-iridescent.
- ^ a b c d Dunn, Jon L. & Alderfer, Jonathan (2006). National Geographic Guide to the Birds of North America. National Geographic Society. ISBN 1-4262-0072-2.
- ^ a b Bellrose, Frank C. & The Audubon Society (1983). The Audubon Society Master Guide to Birding. National Geographic Society. ISBN 1-4262-0072-2.
- ^ a b Madge, Steve; Burn, Hilary (1988). Waterfowl: an Identification Guide to the Ducks, Geese, and Swans of the World. Boston: Houghton Mifflin. ISBN 0-395-46727-6.
- ^ Zimmerman, Dale A.; Turner, Donald A.; Pearson, David J. (1999). Birds of Kenya and Northern Tanzania. Princeton University Press. ISBN 0-691-01022-6.
- ^ Robert S. Ridgely & John A. Gwynne, Jr. (1989). Birds of Panama with Costa Rica, Nicaragua, and Honduras. Princeton University Press. ISBN 0-691-08529-3.