Tundra Swans are smaller than Trumpeter Swans with a little more dish in the bill and a yellow mark at the bridge. The brown stains you see on two of these swans are the product of the alkalinity and other minerals in the marsh water. Although these swans congregate in massive numbers where people can view them from the road, they are quite wild and will fly if approached.
I always welcome the opportunity to photograph whitish birds like gulls and Snow Geese against clouds and blue sky. I’m not sure why but it really seems to make a flying bird “pop” as they say.
Canon 7D, EF 400mm f5.6 L, AV, 1/2000 sec, f5.6, ISO 125, no flash