A study spearheaded by the Wildlife Conservation Society and the University of Minnesota has shown that the world's largest owl -- and one of the rarest -- is also a key indicator of the health of some of the last great primary forests of Russia's Far East. The study found that Blakiston's fish owl relies on old-growth forests along streams for both breeding and to support healthy populations of its favorite prey: salmon. The large trees provide breeding cavities for the enormous bird, which has a two-meter (six-foot) wingspan. And when these dead, massive trees topple into adjacent streams, they disrupt water flow, forcing the gushing river around, over, and under these new obstacles. The result is stream channel complexity: a combination of deep, slow-moving backwaters and shallow, fast-moving channels that provide important microhabitats critical to salmon in different developmental stages. The study was published online on August 6, 2013 in the journal Oryx. Authors include Dr. Jonathan Slaght of the Wildlife Conservation Society, Dr. R. J. Gutiérrez of the University of Minnesota, and Dr. Sergei Surmach of the Institute of Biology and Soils (Russian Academy of Sciences). The authors studied the foraging and nesting characteristics of Blakiston's fish owl in Primorye, Russia, where they looked at nesting habitat over 20,213 square kilometers (7,804 square miles). They found that large old trees and riparian old-growth forest were the primary distinguishing characteristics of both nest and foraging sites. The authors say that management and conservation of old-growth forests is essential for sustaining this species because they are central to the owls' nesting and foraging behavior.
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