World’s largest owl, new research

From Wildlife Extra:

Huge trees help huge owls

World’s largest owl, the Blakiston’s fish owl – and their favourite food – rely on huge trees for breeding and feeding

September 2013. A new 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.

Relies on old-growth forests along streams

The study found that Blakiston’s fish owl relies on old-growth forests along streams for both breeding and to support healthy populations of their favourite prey: salmon. The large trees provide breeding cavities for the enormous bird, which has a two-metre (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 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 kilometres (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.

12 species of owl, tigers & bears

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 behaviour. Moreover, conservation of Primorye’s forests and rivers sustains habitat for many other species: including eight salmon and trout species that spawn there; some of the 12 other owl species found in Primorye; and mammals like the endangered Amur (or Siberian) tiger, Asiatic black bear, and wild boar. Listed as Endangered by IUCN, Blakiston’s fish owl is restricted to riparian areas in Russia, China, Japan and possibly North Korea.

“Blakiston’s fish owl is a clear indicator of the health of the forests, rivers, and salmon populations,” said lead author Jonathan Slaght of the Wildlife Conservation Society. “Retention of habitat for fish owls will also maintain habitat for many other species associated with riparian old-growth forests in the Russian Far East.”

Logistical and financial support for this study was provided by the Amur-Ussuri Centre for Avian Diversity, with additional funding from the Bell Museum of Natural History, Columbus Zoo Conservation Fund, Denver Zoological Foundation, Disney Worldwide Conservation Fund, Minnesota Zoo Foundation, National Aviary, National Birds of Prey Trust, United States Forest Service-International Programs, and the University of Minnesota.

The study appears in the August issue of the journal Oryx. Authors include Jonathan Slaght of the Wildlife Conservation Society, R. J. Gutiérrez of the University of Minnesota, and Sergei Surmach of the Institute of Biology and Soils (Russian Academy of Sciences).

Related articles

• World’s biggest owl depends on large old trees (ecobooks4kids.wordpress.com)
• World’s Largest Owl Exposes Health of Russia’s Forests (livescience.com)
• World’s Largest Owl is Key to Conserving Forests in Russia (scienceworldreport.com)
• World’s Largest Owl Needs Equally Large Trees and Forests (But It’s More Complex Than That) (blogs.scientificamerican.com)