Teal.

[RobinHood]

Southern Ontario this morning.

At the time I was fairly sure it was Green-winged - despite the early morning light fairly dark overall, pale rear end but no definite streak, couldn't see any eye arcs.

However the bill looks really chunky so just interested in other opinions to be sure.

Thanks.

[Birds are cool]

I do not think that your bird is a teal. It has yellow on the bottom of its bill, and i agree with the bill seeming to chucky. Why not a small female/ imm. male mallard.

[IKLland]

My gut reaction was also Mallard. 

[RobinHood]

24 minutes ago, Birds are cool said:

I do not think that your bird is a teal.

You've got me wondering now. I initially saw a duck much smaller than the adjacent Mallards with an all black bill.

Attached another photo.

[Charlie Spencer]

1 hour ago, Birds are cool said:

I do not think that your bird is a teal. It has yellow on the bottom of its bill, and i agree with the bill seeming to chucky. Why not a small female/ imm. male mallard.

There's also white on the undertail.

[Bird-Boys]

All birds are mallards.

[Avery]

5 hours ago, Birds are cool said:

I do not think that your bird is a teal. It has yellow on the bottom of its bill, and i agree with the bill seeming to chucky. Why not a small female/ imm. male mallard.

Looks like a young bird almost reaching adult size. It still has a puff-butt!

[von Humboldt]

The two birds in the first picture are definitely mallards. The one on the right with the yellow bill is a male in eclipse plumage or possibly a juvenile.
The second picture – the three birds in front are mallards as you can clearly see white tails on all of them. I'm unsure of the bird in the back as you cannot see the tale or shape due to the shadows and the bill sure looks solid black. It's probably a female juvenile mallard whose bill is just starting to turn, but I can't eliminate teal. Maybe others can point out something distinctive in that bird to say why it is a mallard.