How do we reconcile the hearing of the torment of the grave by animals (excluding humans and jinn) with our observation of birds living and chirping in the graves of disbelievers in Europe without fear or flight?

The torment and bliss of the grave are established by continuous transmission (tawatur), as is the hearing of animals of the sounds of those being tormented. The observation of birds and their not shying away from the graves of polytheists does not mean that they are not being tormented, for the torment of the grave is part of the unseen (ghayb) which must be believed in. Allah willed to conceal this in order to distinguish the people of faith from the people of disbelief. Birds are not startled by a sound if they are not the intended recipients of it, and the cultivation of land and the greenery of graves have no relation to torment or bliss. These matters should not cause confusion to a believer's faith.