Petrels form a strange group of seabirds. They have a thick bill with two elongated nostrils. They use these nostrils to get rid of salt. They have a salt gland in their head so that they can drink seawater and remove excess salt. Petrels spend the greatest part of the year at sea. There are two separate families: petrels, which include the fulmar and the manx shearwater, and the storm petrels, such as the Leach's storm petrel.