Motion detection or time lapse? A comparison of camera trap triggers in the monitoring of elusive ground dwelling birds

Wildlife cameras have emerged over the recent years as an effective research tool for collecting various types of data on wild animals, and they are used increasingly also in avian studies. However, choosing the best method to collect data depends on the aim of the research and the characteristics of the target species and its habitat. Here, we compared the performance of game cameras taking images by passive infrared motion sensitive (PIR) and time-lapse triggering in gathering occurrence and relative abundance data of the taiga bean goose (Anser fabalis fabalis) in peatlands across Finland in 2020-2021. We found the time lapse trigger mode to be more efficient in collecting data on goose presence than PIR triggering. However, there was no significant difference in the goose numbers between the two trigger modes. We also found the capture probability and relative abundance to vary between years, but this could be attributed to random inter-annual variation. In general, we find time lapse to be a more suitable method to study elusive ground dwelling birds like the taiga bean goose due to fewer required visits to camera sites compared to motion triggered cameras that may produce a lot of empty images due to false triggering. This reduces the disturbance to the geese and other wildlife during the sensitive breeding period.