MEDFORD, Ore. -- Researchers say they have learned why invasive barred owls are thriving while native spotted owl populations are slowly disappearing. The barred owl and the spotted owl are like a pair of siblings. Theyre closely related species, and they compete over everything. They compete over the best trees to roost in. And for the best food source too, juicy flying squirrels. But barred owls are less picky. And that gives them an edge.