Findings show Barred Owls may be bullies of the Pacific Northwest
Much has been done since 1990 to thwart the decline of the threatened northern spotted owl. As such, this shy and secretive predator of the Pacific Northwest has been the focus of intense controversy, mostly due to stricter timber harvest regulations aimed at protecting its habitat. But a new kid in town may be adding to the spotted owls’ woes. The barred owl, a species historically restricted to eastern North America, is expanding its range to overlap that of the northern spotted owl and may be causing spotted owls to abandon their territories. To begin to tease out what is happening in this complex system, Colorado State University researchers Nick Van Lanen and Dr. Kathryn Huyvaert, as well as NWRC’s Dr. Alan Franklin, examined whether barred owls might be excluding northern spotted owls from their territories through interference competition. Interference competition is a fancy way of saying the owls bully each other through physical attacks and aggressive vocal displays. In a series of field trials, researchers used taxidermy mounts and recorded vocalizations to see how each species would react to the other intruding upon their territory. Barred owls were more likely to respond with higher levels of vocal and physical aggression to northern spotted owl mounts and calls, than vice versa. Thus, researchers believe barred owls may be a factor in the continuing decline of northern spotted owl populations in areas where the species co-occur.