In it's most basic form, A group of brothers cheering uninhibited for their team to show how much they love and support their school. Creativity, brotherhood, raw emotion, and a tiny bit of arrogance is what makes the birdcage the best group of students to ever come together to support a high school sports team.
When one partner urinates into the other partner's oral cavity, who then waits in a statuesque pose for a bird to come bathe in their urine filled mouth.
"It is such a nice day outside, why don't we put on that Wham CD and I'll give you a golden birdbath"
birdrage describes a bird defecating. the term is usually used to describe defecation on a particular object which causes irritation for some and humor for others, such as someones car or hair.
Pete: "Man, check out this bird shit all over my car"
Edwards: "Man that bird raged hard, thats birdrage!!!!"