The phrase "black crows" refers to a group of crows that are black in color. It can also be used metaphorically to describe something negative or ominous. Full definition
Tabaimo's at once humorous and meditative single - screen video installation hanabi - ra (flower petal) opens with black crows scattering to reveal the nude posterior of a standing man, covered in what appears to be floral tattoos. (jamescohan.com)