I didn't believe my son the Cabela's field tester. He mounted a speaker on the roof of the pick-up and turned on the distress call tape [in the middle of suburbia]. From seemingly out of no where, flocks of crows came and circled...talking back to the tape. It was spell binding. He is frequently called upon by farmers to take-care-of these nuisance birds.
Best he did was 87, not quite a 834 crow day.