RUSSIA — Rada Surmach strained to hear the mournful echo of nesting owls, deep in the Tunsha River Valley of the Russian Far East. In the twilight, she finally heard it: The duet of the Blakiston’s fish owl, an endangered species whose six-foot wingspan makes it the world’s biggest owl. …Rada Surmach, a researcher at the Federal Scientific Center of the East Asia Terrestrial Biodiversity in Vladivostok, has created a long-term conservation plan to reintroduce captive-bred fish owls to the Land of the Leopard National Park. …Today, by far the greatest problem for Primorye’s fish owls are logging roads. These roads are legally built, but since the 1980s, the number of roads has grown more than 17-fold. Although fish owls mostly nest in tall, dead trees of no commercial value, logging roads allow people such as poachers, illegal loggers, and pine nut collectors access.