In the Spring the wanton lapwing gets himself another crest;
In the Spring a livelier iris changes on the burnish'd dove;
In the Spring a young man's fancy lightly turns to thoughts of love.
From Locksley Hall by Alfred Tennyson
The egret you see here is in all his glorious breeding regalia with lots of long, wispy plumes being shown in a peacock-like display. The long plumes are called aigrettes and occur only when breeding. Also notice the bright lime green coloring at the base of his bill, in an area known as the lores. This green coloring will also go away when breeding time has passed.
Because the aigrettes were so highly prized for ladies' hats in the late 19th and early 20th centuries, about 95% of Great Egrets and Snowy Egrets were killed and the birds almost became extinct. The Migratory Bird Act of 1913 put an end to the carnage.