A few examples of avian tool use have been reported, but in many cases the birds were captive animals and it was difficult to assess the advantage their wild counterparts could glean from the behavior. In the new work, Douglas J. Levey of the University of Florida and his colleagues studied wild populations of burrowing owls (Athene cunicularia). The researchers removed all traces of mammal dung from the nests of two owl populations in Gilchrist County, Fla. Half of the nests then received an amount of dry dung typically found surrounding a nest. After four days, the researchers analyzed the birds droppings and collected discarded remains of eaten beetles to determine the owls diets. They discovered that owls with access to dung ate 10 times more dung beetles than those with bare nests did.
The scientists also tested whether the owls might be using the dung to mask the scent of their nests, but found that it did not offer sufficient protection from predators. Instead, the owls appear to fish for dung beetles using excrement as bait. The results of this study, the authors conclude, provide an unambiguous estimate of the importance of tool use in a wild animal.