Green’s Dictionary of Slang

shitbird n.1

[shit n. (5a) + bird n.1 (3a)]

a narcotic drug abuser, a heroin addict.

[US]D. Simon Homicide (1993) 247: [...] putting the handcuffs on the most mindless shitbirds.
[US](con. 1964–8) J. Ellroy Cold Six Thousand 91: Wicked Wendell [...] a rape-o/a shitbird/a heel.
[US]N. Green Shooting Dr. Jack (2002) 220: ‘That’ll be the day,’ the black one growled at him, ‘I let these shitbirds dictate where I can go.’.
[US] M. McBride Frank Sinatra in a Blender [ebook] What do I look like, shitbird? I don’t known nothin’ about whatever it is you think I know.