Sometimes, from a distance, a Northern Shoveler can look like a Mallard to me. But it’s fun to see the ducks swimming in groups of concentric circles like in the zoomed-in photo above—then I can be pretty sure they’re Shovelers that I’m looking at, as they go round and round sifting the water near the surface for food with their bills.
When the lake freezes over, the birds have to squeeze into a smaller space in the un-iced parts of the lake, but the different species of ducks co-exist surprisingly well considering that they are all after a similar limited food supply of small plants and fish in the constrained area.
In this picture you can see the large Canadian Geese, the male and female Mallards with their wings spread, the small American Coots with their white bills and dark bodies, and lastly, a bunch of Northern Shovelers, standing in the back and floating in the water, dark green head and dark, flat-ended bills, and bodies with white breasts and brown flanks.
It was fascinating to see all these different kinds of birds band together and turn around as one when a few aggressive gulls approached; the gulls were not welcome to this party—perhaps they would not play well with others?—and the ducks soon mobbed the gulls and forced them to go elsewhere.