Carla, I'll bet those crows thought your father was plucking a crow
(they're smart, but they're not that smart). Crows are very sensitive to
seeing one of their own kind killed, or I suppose in danger, as befits a
social species. As was mentioned on tweeters some time ago about mobbing, I
guess it doesn't matter if it is a related individual or not. As a control,
ask him to pluck a white chicken some time when crows are around! Another
test would be merely to grab a black chicken and set it squawking to see if
the crows were interested; I wouldn't think they would be so attentive if
they knew it wasn't a crow.

Dennis Paulson
Slater Museum of Natural History
University of Puget Sound
Tacoma, WA 98416