We have a stream running through our back yard in Downers Grove, so we often get mallard ducks in our back yard. Sometimes they nest (although they've never successfully hatched their eggs), other times they just hang around. Usually, it seems to be the same pairs.

Last summer and this year, we've had a male mallard showing up with a female with significantly darker feathers than most female mallards, and a large white patch on her breast. Is this just some sort of variation on what a female mallard can look like, or is he hanging out with a different breed of duck? They seem to be a pretty dedicated couple.

You can see a photo at: https://goo.gl/photos/cecXM8GrqDFHMH97A

Thanks, Bill Pardue