The term 'bird diving' refers to the act of birds plunging into water in order to catch prey. OSPREY (6 letters) is a large bird of prey that dives into water to catch fish. LOON (4 letters) is a type of aquatic bird that dives underwater to catch small fish and aquatic invertebrates. AUK (3 letters) is a seabird that dives underwater to catch small fish and crustaceans. PETREL (6 letters) is a type of seabird that dives into the ocean to catch small fish and squid. All of these birds use their wings to propel themselves underwater and have adapted to be able to hold their breath for extended periods of time while they search for food.