Given the task definition and input, reply with output. In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.

Passage: The diet of pelicans usually consists of fish, but occasionally amphibians, turtles, crustaceans, insects, birds, and mammals are also eaten. The size of the preferred prey fish varies depending on pelican species and location. For example, in Africa, the pink-backed pelican generally takes fish ranging in size from fry up to 400 g (0.9 lb) and the great white pelican prefers somewhat larger fish, up to 600 g (1.3 lb), but in Europe, the latter species has been recorded taking fish up to 1,850 g (4.1 lb). In deep water, white pelicans often fish alone. Nearer the shore, several encircle schools of small fish or form a line to drive them into the shallows, beating their wings on the water surface and then scooping up the prey. Although all pelican species may feed in groups or alone, the Dalmantian, pink-backed, and spot-billed pelicans are the only ones to prefer solitary feeding. When fishing in groups, all pelican species have been known to work together to catch their prey, and Dalmantian pelicans may even cooperate with great cormorants. They catch multiple small fish by expanding the throat pouch, which must be drained above the water surface before swallowing. This operation takes up to a minute, during which time other seabirds may steal the fish.
What beats their wings on the water surface?