Assessing the impacts of manipulative research can be hard when few animals are affected in any one study. Collating information across studies, however, can identify vulnerable organisms and allow researchers to tailor research to reduce, and possibly eliminate, adverse effects. Relatively few studies have documented radiotransmitter impacts on passerine birds. We hypothesized that many studies do not publish problems, and that this lack of reporting hampers improvement of methods. We used an online survey to gather information from researchers about the species affected and the nature of any impacts. Sixty respondents provided information concerning ≥63 passerine species. Negative transmitter impacts were reported for ≥1 bird for 38% of species. Entanglement with vegetation or body parts and nonentanglement-related injuries affected 27% and 19% of species, respectively. Simultaneously, 29% and 33% of species were reported to have caused transmitter damage and lost transmitters, respectively. Only 2 respondents indicated that they had documented these problems in the peer-reviewed literature. The occurrence of negative transmitter effects was similar for adults and juveniles, for transmitters attached with glue or harnesses, and regardless of bird mass. Ground-foraging passerines were significantly more likely than other passerines to have experienced transmitter loss, entanglement, and nonentanglement injuries. Our study suggests a clustering of problems in grassland passerines. We make suggestions to identify and collate problems related to negative transmitter impacts in passerines to help reduce harmful effects on birds and wasted research effort. © 2011 The Wildlife Society.