Live decoys: an old but effective tool for attracting, capturing, and studying free-living passerines

Passerines are elusive animals, and their capture generally requires considerable fieldwork. This study describes the capture and sampling of free-living birds from two of the most illegally trafficked Brazilian wild passerine species, namely the red-crested cardinal ( Paroaria coronata ) and green-winged saltator ( Saltator similis ). The study is part of the planning process for a rehabilitation and release program for confiscated conspecifics of both species. A total of 290 free-living wild passerines were captured, and most of them were sampled, banded, and immediately released at the same site. Blood, feces, and oropharyngeal swabs were collected for subsequent health analysis and blood drops were stored on FTA cards for genetic assessments. Conspecific live decoys played an important role in the trapping process, especially those with a high-ranking for dueling behavior and vocal performance. Most of the green-winged saltators that promptly engage in combat were caught with netted trapdoors. However, red-crested cardinals are shy, cautious, open-area passerines that seldom perch on unknown objects. These were mostly captured in loop snares after they perched on tree branches used as triggers. Although mist netting was more difficult to install and captured the most non-target species, it was the fastest technique and also provided comparable numbers of captures for both target species. Despite being an old and well-established practice, detailed information on the use of live decoys for capturing free-living passerines is scarce.