Jackdaw

This is a jackdaw and not a crow. The jackdaw differs from the crow because it is smaller, it has a gray back, a relatively small beak and an iris.
The bird can also be recognized by the typical call that sounds like kjack, kjack.

The jackdaw usually lives in pairs, but sometimes also form large swarms, often together with other jackdaws. The nest is built on chimneys or tall buildings and is made of branches. The jackdaw is a social bird, the male and the female also live together outside the breeding season and usually stay together for the rest of their lives. The jackdaw, like many other crows, has adapted well to humans and therefore occurs in large numbers in cities.

Also in our environment you often see large groups.