Help with bird ID

Maybe this should be in Avian but I thought I'd give this a try and see what the result would be.
I took this picture and the one in the first message below, yesterday at the botanical gardens in Montreal. The ducks there are wild and there are no domesticated animals.
This guy was with the mallards but was a bit bigger even than the largest males. He has a darker beak but has a violet wing patch that is white on both sides.
The pictures are for ID only.
Thanks for any help.
Rick T

Here is the other shot.
Rick T

Mallard hybrid?
There's an in-city lake near where I live that has permenant resident wild ducks and geese. We see things like this too, where it looks like there has been some hybridization going on. If it's bigger than a mallard perhaps one of its parents was a goose... Just guessing...

Certainly has the traits of a female Mallard, but is also a bit different. These are the ones that hang at the lake in the Japanese gardens (where the colorful fish are), right?

Wikipedia says quite a bit about hybridization and stuff: http://en.wikipedia.org/wiki/Mallard

I have not seen this guy until last week. I've seen most of the summer residents and probably would have spotted this one earlier. Here is one more shot I took today to show the size comparison.
Rick T