These Hooded Mergansers were swimming and diving for food at the edge of the ice in a small, half-frozen pond on Long Island, NY.
When I snapped this picture, I thought both of these Hoodies were female. But I discovered that the one on the left is an immature male and the other is an adult female. Note the different colors of the bill, eye, and head. They both have head crests, but the male’s is flattened back and the female’s is half-raised.
Here’s another look at the young male with his head crest.
When the male grows up, he’ll look like this (photo taken at the same pond several months earlier):