Perch-Mounted Camera Traps Record Predatory Birds in Farmland

Abstract

Artificial perches can attract raptors to farmland, where the raptors perform an ecosystem service by consuming insect or rodent pests; however, such perches have not enjoyed widespread use. We used an improved camera trap installation method to record birds on perches, and to test perch height preference of raptors and other species. Our study area was in a mosaic agriculture system, the typical farming environment in Asia. Our “double-branch” perches consisted of a main pole with a branch at the top and in the middle, 8 and 4 m from the ground, respectively. Each branch was equipped with a camera trap, with the focus adjusted to close range. From April to July 2020, the installations at five different crop fields provided a total of 83,740 photographs with birds, including 27 avian species. Photographs of raptors and insectivorous birds accounted for 80.1% to 99.7% in each field. The most frequently recorded raptors were the Black-winged Kite (Elanus caeruleus) and the Collared Scops-Owl (Otus lettia). The most frequently recorded insectivorous birds were the Black Drongo (Dicrurus macrocercus) and the Brown Shrike (Lanius cristatus). The kites preferred to stand on the upper branches, whereas the owls and most of the insectivorous birds tended to choose the lower branches. By our method, numerous clear photographs of birds can be obtained and used to analyze visit frequency, activity patterns, and captured prey. Moreover, we showed that different species used artificial perches of different heights. Artificial perches could be more widely used for enhancing and quantifying avian ecosystem services, and promoting raptor-friendly farming.