Do you see them gathering mostly at dusk? If so, there must be a crow rookery nearby.

When I was growing up in San Mateo, I don't recall seeing any crows. I would see them in Southern Cal and figured they liked warmer weather. Then I moved to Seattle and found that there were tons of crows up here.

We have a rookery about 4 miles from our house. Every evening, you can see hundreds of crows heading east towards the rookery. The area around the rookery will have crows in the trees, on roofs, telephone poles, etc. In the morning you can see them all heading west to do their daily activities.

Crows seem to have taken over the world. Hitchcock was on to something.