Anatomy: Speculum

Waterfowl are just beginning to migrate through Pennsylvania so now’s a good time to learn the name of an important fieldmark on ducks.

The speculum is a patch of distinctive color on the wing.  It is made up of secondary feathers and is usually iridescent on dabbling ducks, as shown here on this female mallard. 

It’s a useful fieldmark when trying to identify mallards and American black ducks.  The speculum on mallards is blue with white borders.  On black ducks it’s purple without white borders.  Unfortunately mallards and black ducks can hybridize and the result can be confusing!

(photo by Chuck Tague)

One thought on “Anatomy: Speculum

  1. Thanks for the great the great tip! It’s very helpful to know about distinctive fieldmarks such as a duck’s speculum. I never knew about the hybridization though, good to know!

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