The Wildfowl Trust, Slimbridge, Gloucestershire T H E A N N U A L M O U L T of the Shelduck (Tadorna tadornd) results in the simultaneous loss of all the flight feathers, but before this happens the great majority of the north European population migrates to a small area in the Heligoland Bight. The existence of this migration was first suggested by Hoogerheide and Kraak (1942), and was confirmed ...

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