§ Of Beren and Lúthien The Silmarillion

Then Beren was aware in his dream of a form that came to him across the water, and it was a wraith of Gorlim; and it spoke to him declaring his treachery and death, and bade him make haste to warn his father. Then Beren awoke, and sped through the night, and came back to the lair of the outlaws on the second morning. But as he drew near the carrion-birds rose from the ground and sat in the alder-trees beside Tarn Aeluin, and croaked in mockery.