Crows are jet black birds that attack and kill any weak animal that can't defend themselves. However, they are not a major enemy or ally to the rabbits.
Crows appear and are mentioned several times in the book. Notably, whilst Hazel's group is crossing a field, Pipkin, who has fallen behind, is attacked by a crow. Bigwig immediately comes to Pipkin's defense and drives the bird off.
During his chapter, it is revealed that General Woundwort once fought and defeated a crow.
After taking shelter in the ruins of a church, Hazel's group encounter a flock of crows led by a certain large individual. Hazel tries to talk to the crows, apologizing for their intrusion, but the crows instead attack the rabbits, resulting in a fierce battle. It ends when Bigwig kills the crow leader by biting its throat, causing the rest to flee.