We don't have synonyms for hagdon yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are hagwon, haddon and haydon.
(n) :
(regional, now rare) One of several species of sea birds of the genus Puffinus, especially, Ardenna gravis (syn. Puffinus gravis, Puffinus major), the great shearwater, and Puffinus stricklandi, the black hagdon or sooty shearwater.
(n) :
(regional, now rare) One of several species of sea birds of the genus Puffinus, especially, Ardenna gravis (syn. Puffinus gravis, Puffinus major), the great shearwater, and Puffinus stricklandi, the black hagdon or sooty shearwater.