Crows want everyone else to know that they're there:

Crows make a lot of noise at night, but it isn't necessarily an attempt to scare anyone away. In fact, some crow species make noises in order to let other crows know that they're present in the area. The more noise there is, the larger their territory will be!

Why are the crows cawing so much?

One of the reasons why crows or ravens caw, then, is to give off a particular signal to those it encounters. When detecting the presence of other hostile individuals or other unknown birds, crows emit a short and low pitched caw. Ethologists interpret this as an attempt to look larger and more threatening.

How do you get crows to shut up?

Just how do you get crows to shut up and stop cawing? In general, anti-bird spikes, loud noises, scarecrows, shiny decorations, decoys, bird netting, and lasers all can scare crows away and stop them from cawing.