These are medium-sized seabirds with long, barrel-shaped bodies, short tails, very small wings and short legs set far back on the body. Most can hardly walk, but stand upright on cliff ledges where they come to breed each spring.
They fly low and fast with whirring wings and poor manoeuvrability, but they are excellent swimmers and divers, using their wings to ‘fly’ underwater.
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Text (c) RSPB, used with permission