The commonest call is a hard, repeated "kraa-kraa". The repertoire is large and varied, however, and crows can both mimic other sounds and show local differences in their calls. The Hooded Crow is among the most vocal and communicative of our birds and uses different calls to warn, keep in contact and defend territory. The crow's "kraa" is drier and less deep than the Raven's hollow "korp-korp", which is a useful way of telling the two species apart by call alone.