Sub-lingual oral fistulas in Sooty Terns (Onychoprion fuscata)

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Sub-lingual oral fistulas are a condition first reported in New Zealand Stitchbirds (Notiomystis cincta) in which a lesion develops on the periphery of the mandible in the oral cavity and a fistula develops through which the tongue protrudes. We report that it arises in another species, the Sooty Tern (Onychoprion fuscata), breeding on Ascension Island in the south Atlantic. We discovered five adults with oral fistulas out of a total of 13,664 adults and chicks ringed during 11 breeding seasons over 13 years. Compared with other threats to the Ascension breeding population of over 180,000 pairs of Sooty Terns, we report that oral fistulas are a minor threat to colony stability, especially because afflicted birds were incubating eggs. Nevertheless, our findings suggest that further investigations of whether the condition is sex-linked, of its pathogenesis, and of its causation would augment our knowledge of the biology of Sooty Terns; such information might also have conservation implications for our understanding of the condition in endangered Stitchbirds. We call upon ornithologists to report oral fistulas in other species, because it would seem unlikely that these are the only two species predisposed to the condition.


Original languageEnglish
Pages (from-to)691-696
Number of pages6
JournalJournal of Ornithology
Issue number3
Publication statusPublished - 1 Jul 2009


  • Ascension Island, Deformity, Pathology, Handicap, Tongue, Seabird