By Elise Brosnan
The Spotted Owl just can’t get a break. Endemic to old-growth forests in the Pacific North west, the endangered owl’s population was already declining due to deforestation, but now they have been forced to accommodate an inconsiderate guest: Barred Owls. Native to the eastern half of North America, the Barred Owl’s territory has been expanding westward since the turn of the last century. By the 1990s, Barred Owls have become a permanent fixture throughout much of the Spotted Owl’s historic range. Larger, more aggressive, and more opportunistic than Spotted Owls, Barred Owls have been identified as a significant new factor driving the Spotted Owl’s population collapse.
However, Spotted Owls hold no apparent ill will towards Barred Owls. The two species occasionally hybridize, or mate, producing an offspring that is half spotted and half barred. As you might expect, “Sparred Owls” look like both of their parents. They have the Barred Owl’s larger size, but the Spotted Owl’s darker coloring. Their breast plumage is a mixture of spots and bars, described as looking like a checkerboard pattern. Their call also reflects their mixed heritage; a series of staccato Spotted Owl-like “hoos” followed by a Barred Owl-like “hoo-ah,” described by a biologist as “sort of like a Spotted Owl being strangled.”
Hybridization is surprisingly common in birds. Up to ten percent of birds are suspected to hybridize with other species, at least occasionally. However, hybridization may be increasing as the historic range of many bird species changes. As we lose grassland in the Great Plains states, eastern forest birds are interacting with western forest birds in a way that has never been seen before. Because of climate change, both western and eastern species are finding northern territories more hospitable. The Barred Owl made its way west by colonizing Canadian forests at the very north of its range, before looping south into Spotted Owl territory.
Great Plains hybridization has threatened species before. The Midwestern Blue-winged Warbler is expanding its range eastward, where it outcompetes and hybridizes with the Golden-winged Warbler. (However, some biologists argue that Golden-winged and Blue-winged Warblers are two variants of the same species, and, by definition, cannot be under threat from itself.)
Therefore, what should be done about Barred Owls? Experimental cullings have occurred, with moderate success. However, some environmentalists argue that the arrival of the Barred Owl has provided a convenient scapegoat for another enemy of Spotted Owls: the logging industry. “Competition from Barred Owls may well need to be addressed on an interim basis until Spotted Owls’ populations can be returned to health,” says Bob Sallinger, conservation director of the Audubon Society of Portland, Oregon, “but unless critical habitat needs are adequately addressed, Barred Owl control will be nothing more than a sad and pathetic footnote on the road to Spotted Owl extinction.”
Axelson, G. (2016) Golden-winged and Blue-winged Warblers Are 99.97 Alike Genetically. Living Bird Magazine. Cornell Lab of Ornithology, Ithaca, NY, USA. Retrieved from https://www.allaboutbirds.org/mixed-wing-warblers-golden-wings-and-blue-wings-are-99-97-percent-alike-genetically/