Stable Isotope Analysis as a Tool to Prevent Illicit Wildlife Trade of Songbirds in Brazil

ABSTRACT One of the main causes of biodiversity loss, the illegal trade of wildlife, causes several environmental impacts. In Brazil, songbirds are among the most trafficked groups, particularly those from the Thraupidae family, one of the most diverse avian families, comprising both common and threatened species. The regulation of the trade of wild animals was conceived as a conservation strategy. However, if not carefully managed, this activity can have the opposite effect, intensifying the impact on natural populations through wildlife laundering. Identifying whether a traded animal is captive or wild is a challenging task, but crucial to assessing the legality of the trade. Stable isotope analysis is a powerful tool for indicating animal origin and diet. This technique has proven helpful in differentiating between wild and captive individuals across various studies involving different vertebrate groups. Here, we investigated the use of δ 13 C, δ 15 N, δ 2 H, and δ 18 O to differentiate wild and captive songbirds in Brazil. We analyzed 657 feathers of 58 nonmigratory species from the Thraupidae family distributed throughout the country ( n wild = 341; n captive = 250; n unknown = 66). We tested the differences in isotopic ratios between the two rearing environments and compared seven classification models, using the most accurate to classify our unknown samples. The isotopic values of δ 13 C, δ 15 N, and δ 2 H differed between the wild and captive birds. The Random Forest model performed best, using δ 13 C and δ 2 H as the main predictors to distinguish between the two rearing environments. 37.88% of the unknown samples were classified as wild birds, including individuals with official rings, which indicated they were supposedly born in captivity. We have demonstrated the ability of stable isotopes to distinguish between wild and captive songbirds in Brazil, especially δ 13 C and δ 2 H. Our results suggest that some songbirds have been laundered, highlighting the potential of stable isotope analysis in detecting this illegal practice in Brazil.