Both male and female Great Egrets grow beautiful long display feathers down their backs in breeding season. The male will shake his out and preen as part of his display to attract the female.
I've never given the Cattle Egret it's fair due. They deserve respect. Native to Africa they made their way to South America in 1877, to the northeast in 1941. They started breeding in the US in 1953 and are by now the most abundant egret in the New World. You can find them in Newfoundland! Breeding plummage is identified by the golden color on the head, neck and back.
I was told that when a female is bent over her nest like this she might well be helping one of her babies emerge from it's shell. It is very touching to watch this behavior.