First, if you have outdoor cats, I STRONGLY recommend you don't try to interact with crows.
Please don't. It's a recipe for disaster. Even if the cats don't kill one, even if you do make progress with the birds, at some point they will associate the enemy cats with you and you will also become an enemy. And their memory and enmity last across generations.
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They love dry cat food. I read what I could find and it should be healthy for them. I bought a large bag of Whiskas last year and still have lots left. A lot of people suggest peanuts are their favorites, but when I gave them a choice they always took the cat food first.
Common wisdom is not to look at them when trying to initiate contact as they feel threatened by that. By the time I started reading though, I was already doing everything wrong and having too much success to change.
I started throwing the food out on the lawn when I saw them. I threw it in the open, where they had easy getaway routes and a good view all around them. I would talk to them when they showed up and look right at them. I always moved slowly, but never tried to be sneaky.
The platform came after a trust had been established. I had been feeding them on the lawn and been providing water and chasing cats away. It didn't just happen overnight.
Pay attention to their vocalizations. A lot is just them sharing neighborhood conditions among themselves, but the alarm call is pretty distinct. I go outside when I hear it close by and if I can identify the cause(cat, squirrel, etc) I will chase the 'bad guy' away. Do that a few times and you will go in their good books.
There is a special sound they make when they want to say they like you. I hope you get to hear it.