Speculum feathers explained

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.^[1] The species' common name comes from the sky-blue wing coverts.
• Crested duck and bronze-winged duck: Iridescent purple-bronze, edged white.^[2]
• Pacific black duck: Iridescent green, edged light buff.^[2]
• Mallard: Iridescent purple-blue with white edges.^[3]
• American black duck: Iridescent violet bordered in black and may have a thin white trailing edge.^[3]
• Northern pintail: Iridescent green in male and brown in female, both are white on trailing edge.^[1]
• Gadwall: Both sexes have white inner secondaries.^[3]
• 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.

Notes and References

1. Book: Bellrose, Frank C. . The Audubon Society . amp . 1983. The Audubon Society Master Guide to Birding. 1-4262-0072-2. National Geographic Society.
2. Book: Madge, Steve. Burn. Hilary. Waterfowl: an Identification Guide to the Ducks, Geese, and Swans of the World. Houghton Mifflin. 1988. Boston. 0-395-46727-6. registration.
3. Book: Dunn, Jon L. . Alderfer, Jonathan . amp . 2006. National Geographic Guide to the Birds of North America. 1-4262-0072-2. National Geographic Society.
4. Book: Zimmerman. Dale A. . Turner. Donald A. . Pearson. David J.. 1999. Birds of Kenya and Northern Tanzania. 0-691-01022-6. Princeton University Press.
5. Book: Robert S. Ridgely . John A. Gwynne, Jr. . amp . 1989. Birds of Panama with Costa Rica, Nicaragua, and Honduras. 0-691-08529-3. Princeton University Press.