Surprise!

This isn’t a female mallard.  It’s a mottled duck. 

Though she resembles a mallard, her head and neck are noticably paler than her body and her speculum is light blue instead of purple.  (Here’s the speculum on a female mallard.)

The mottled ducks’ lifestyle is very similar to the mallards’ except that these live only in Florida and along the Gulf coast. 

Not in Pennsylvania.

(photo by Chuck Tague)