Crows trapped by a researcher in a mask still scold that exact mask five years later
Researchers in Seattle trapped and banded crows while wearing a distinctive mask, then released them. Years afterward, crows across the area scolded anyone wearing that same mask, even disguised with a hat or worn upside-down, while ignoring a neutral control mask entirely. Young crows born after the original trapping joined the scolding too, apparently learning the grudge from their parents, and some mobbing behavior was still being observed roughly five years later.