I believe this is a green winged teal. If I am wrong let me know. This is one of the many birds I saw in London in one of the parks.
The green winged teal is a dabbling duck. According to Ducks Unlimited they visit shallow waters such as flooded fields and marshes. They feed by tipping up rather than diving.
I am still going back to the many bird photos I took in England and trying to identify them. Happy Columbus Day if you are in the U.S. Happy Thanksgiving if you are in Canada!
Sharon's Iconic Travel Photography Blog 