Identifying these birds took a lot of online research, but I found pictures just like them. They are Wood Ducks, whether they are immature males that haven't yet developed the distinctive crest on their head, or non-breeding birds as was stated by some, isn't clear to me.

A photo said to be of a non-breeding wood duck is seen here - http://www.pbase.com/nsxbirder/image/102682262 Other photos online seemed to indicate they have not yet fully developed distinctive characteristics of the adult wood duck. These are the first like this I have ever seen.