The fledging of common and thick-billed murres on Middleton Island, Alaska

Three species of alcids, Common and Thick-billed murres (Uria aalge and U. lomvia) and the Razorbill (Alca torda), have post-hatching developmental patterns intermediate to precocial and semi-precocial modes (Sealy 1973). The young leave their cliff nest sites at about one quarter of adult weight and complete their growth at sea. At departure, an event here loosely referred to as "fledging," neither primary nor secondary flight feathers are grown, but well-developed wing coverts enable limited, descending flight.