Integrated Pest Management in Idaho: Discovering the Diet of Idaho Barn Owls

Farmers in Idaho’s canyon county have a pest problem: gophers (Thomomys townsendii). These agricultural pests eat or otherwise damage crops and dig holes that disrupt fields and irrigation canals. To reduce the number of gophers without the use of harmful rodenticides, which have the potential to poison secondary wildlife, Canyon County Weed and Gopher Control has developed an integrated pest management program. This program included installing barn owl (Tyto alba) nesting boxes with the intention of attracting barn owls that would reduce gopher numbers through predation. But do barn owls actually prey on gophers? To find out, we collected regurgitated owl pellets found in and around nest boxes that were analyzed for prey contents. Based on analysis of 1,552 pellets from 47 nest box sites, we found 24 different prey species. The main staple of an Idaho barn owl’s diet was the mountain vole (Microtus montanus). The mountain vole made up 67.6% of the prey items found in the pellets analyzed. Only a small percentage of prey items were gophers (2.3%). Although gophers make up a small percentage of barn owl diet, the boxes have still been somewhat effective in controlling the gopher and other rodent populations based on our prey analysis and comments from local landowners about observed declines in gopher damage in fields. Thus, integrated pest management with barn owls is a viable option compared to labor intensive gopher trapping or the use of pesticides