In past, often treated as conspecific with F. tropica; relationships between these two are complicated and confused, and several further species may be involved; genetic study may supply some answers. Situation particularly muddled with regard to birds of Tristan da Cunha and Gough I, where two different forms appear separable at least on biometrics, those of Gough being smaller and shorter-winged but longer-legged#R; race leucogaster sometimes ascribed to F. tropica; some claim that a white-bellied form of F. tropica occurs in these islands, representing either a morph or possibly a race (melanoleuca); if two different taxa do breed in these islands, name leucogaster would appear to refer to smaller birds (Gough) and melanoleuca to larger ones (Tristan)#R. Very large race titan may be more appropriately treated as a full species. Four subspecies currently recognized.
Food and feeding
Status and conservation
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