A group of crows is called a Murder of Crows

It is likely that if you see a great number of crows

That the death of one of their number has taken place

 

It is also thought that they are in mourning

As crows are known to be emotional creatures

 

Another explanation notes

That they need to know

What killed the unfortunate crow

So that they might avoid the same fate

 

In the Bible, if a crow is weeping in a tree,

It means that it is not weeping elsewhere

 

 

From Notes on Crows (1891)