Distance and size matters: a comparison of six wildlife camera traps and their usefulness for wild birds

Camera traps are increasingly used in ecological research. However, tests of their performance are scarce. It is already known from previous work that camera traps frequently fail to capture visits by animals. This can lead to a misinterpretation of ecological results such as density estimates or predation events. While previous work is mainly based on mammals, for birds, no data about if and how camera traps can be successfully used to estimate species diversity or density are available. Hence, the goal of our study was an empirical validation of six different camera traps in the field. We observed a total number of N=4567 events (independent visits of a bird) in 100 different sessions from March 2017 until January 2018, while camera traps were deployed. In addition, N=641 events are based on a comparison of the two close-up camera traps especially designed for birds. These events were all directly observed by the authors. Thus, the cameras can be compared against the human observer. T...