The female is...
Bigger. About 1/3 larger than the male.
Has a heavier brow. Looks a little more evil.
The male...
Is about 2/3 the size of the female.
Has a brilliant, bright white head.
Has a speck "beauty mark" on his check.
Has "guyliner," a black line around his eyes that makes his eyes pop out more.
And generally he looks a little more feminine and prettier than the female I think.
There's something about the length their beaks go back but I'm blanking on what that is.
And there's a good Youtube video that shows how to tell them apart.
Here it is...
Here's a funny video from last year.
They kept moving that corn husk around when the other one took a shift on the nest. They have an incubation path on their belly area and they wiggle to get the eggs close to their skin to keep them warm. Hence the "shimmy." That's what they're doing.