Peregrine Falcon enjoying...whose foot is that??

I spotted this Peregrine Falcon perched on top of a utility pole just east of Canon City. I positioned by car so I could photograph from inside, using the car it as a blind, to try to avoid disrupting this bird's meal. Soon after I started taking photos I was surprised to see the Peregrine with a very large foot in it's beak. I had thought it had a duck since it was a large meal and it was very near the Arkansas River; however, this is not a webbed foot but a foot that looks like it came possibly from another raptor as it is not only quite large but has very long nails. It's yellowish foot and leg with the long claws look a lot like that of a Cooper's Hawk's foot, or maybe a  Sharp-shinned foot, but I am open to other species.

Though I was successful in avoiding flushing this Peregrine it did look at me a few times presumably in response to the mechanical sounds of my dslr camera. More pics to follow. SeEtta