From military slang and jargon. A term used to describe anything that is unacceptable or just downright shitass. Also a term of endearment for friends. See also: shitass
"Tweet tweet. Here comes the bird. The Shit-Bird!"
"Hey, shitbird, can you hand me that church key over there?"
"Shitbird! I can't beleive that I forgot my keys in the car."
"This thing is so shitbird. Who would design something to work like this."