‘Cah! Cah! Cah! Cah!’ (And yes, I’m familiar with the crows that are being killed in Boston.) This is the call when I toss some unsalted peanuts in the shell or other goodies into the yard. (Crows make marvelous garbage disposals.) One (perhaps there’s only one or two in the trees) will call out, and I’m guessing it’s letting the rest of the flock know there’s good eats. Usually one a brave one or two will come down while I’m sitting on the patio, followed by some more when those see I’m not eating the first ones. But sometimes they’ll sit in the trees and launch into the Cah Cah Chorus. It doesn’t seem to be useful for them to signal there’s food, since they’re already there and can see it.
Also, what does the ‘rooooook!’ sound they make mean?