Sentence:  He ran back and picked up a dead bird that had fallen. It was not a duck but a <WSD>shag</WSD>. 
Meaning of the word marked with <WSD> tags:  Several species of sea birds in the family Phalacrocoracidae (cormorant family), especially the (common shag) or European shag, "Phalacrocorax aristotelis", found on European and African coasts.