The Sincorá Antwren is restricted to the Serra do Sincorá in the Chapada Diamantina, Bahia. It is found in campos rupestres (rocky montane scrub) while the similar Rusty-backed Antwren F. rufa is found in cerrado, borders of gallery forest and white-sand forest. It differs from Rusty-backed Antwren in having darker and less rufous upperparts, less yellow on the flanks and having underwing coverts that are grey and white as opposed to pure white. Sincorá Antwren Formicivora grantsaui is found only in the campo rupestre vegetation of the Serra do Sincorá between 850 m and 1,100 m in the Chapada Diamantina region. First observed in 1997, it is closely related to Rusty-backed Antwren Formicivora rufa, with which it sometimes occurs sympatrically. It differs slightly in some plumage characters but more importantly it has quite distinctive vocalisations and each species utilises different habitats. Formicivora grantsaui occurs on rocky outcrops in the campo rupestre and F. rufa in the adjacent savannas.
Gonzaga, Luiz Pedrera; Carvalhaes, André M. P. & Buzzetti, Dante R. C. (2007) A new species of Formicivora antwren from the Chapada Diamantina, eastern Brazil (Aves: Passeriformes: Thamnophilidae). Zootaxa, 1473: 25-44.