Looks like we've got a badass over here.
Blakiston's fish owl, the largest owl in the world, makes its home in old growth forests surrounding streams and rivers in Russia's Far East, east China, and Japan. But due to rapidly disappearing habitats, the huge birds—females can hit 10 pounds, which is a lot to fly with—are in decline.
New research published in Oryx explores just how crucial old growth forests are to the survival of the owls, and notes that without big, old trees, the big owls can't survive. With six foot wingspans, it's clear that the birds need large trees in order to breed and nest. But beyond making new owls, big trees are crucial for the productivity of the birds' environments.
As authors Jonathan Slaght of the Wildlife Conservation Society, R. J. Gutiérrez of the University of Minnesota, and Sergei Surmach of the Russian Academy of Sciences explain, the owls rely on streams to find their diet of fish, the bulk of which is salmon. Now, trees fall into rivers all the time, but only old, large trees are big enough to disrupt the flow of a river and create the eddies, riffles, and ponds that are crucial to salmon development.
After surveying 7,804 square miles in Russia, the team found exactly that: The major hallmarks of the bird's nesting and foraging sites were old growth forests and large trees. No surprise, right? But what's really fascinating is that, with the correlation being pretty tight, the reverse may also be true: If Blakiston's fish owls rely on pristine, healthy forests to survive, a decline in the owl population in historic ranges would suggest that the habitat itself is in decline.
“Blakiston's fish owl is a clear indicator of the health of the forests, rivers, and salmon populations,” Slaght said in a release. “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.”
Because the owls have such strict habitat requirements, they thus may act as excellent indicators of habitat quality, as even subtle declines could produce corresponding effects on the birds. An analog is amphibians, which are generally very sensitive to habitat decline and have thus been long studied as indicators of habitat quality. But in this case, instead of a chill frog, we've got a massive, fluffy owl.