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Crows are smart. Look at them and toss some unsalted peanuts in their general direction and they'll understand what you're doing. After a couple of visits they'll recognize you and slowly get more relaxed around you. They each have their own personalities, where some will be easier to befriend than others, so just give them space and time.

My crow bro, Kenny. Most days I go for a walk after work and meet up with him to feed him some peanuts or dog food.