First documented case of combined bill and tarsusdeformities in the Rufous-bellied Thrush Turdus rufiventris Vieillot, 1818 (Passeriformes: Turdidae)

Abstract

Morphological deformities in birds are rare and may reflect genetic, nutritional, or environmental factors. We report an adult Turdus rufiventris Vieillot, 1818, captured in an urban area of Central Brazil, exhibiting simultaneous abnormalities in the bill and tarsus. The mandible was excessively elongated, curved, and deviated laterally; the scales on both tarsi were prominent, and two toes on the left foot had duplicate nails. Despite these deformities, the individual displayed an active reproductive condition, body mass within the expected range, and signs of normal feeding, indicating good physiological condition and functional compensation ability. This record represents the first formal report of such a combination of deformities in T. rufiventris in Brazil and contributes to the understanding of the diversity of morphological anomalies in Neotropical birds, emphasizing the importance of continuous monitoring of wild populations, particularly in urban contexts.