Finland’s boreal owl dialect disappearing with old-growth forests in the south

A unique regional “dialect” of Finland’s boreal owl is vanishing from southern Finland as ancient forests decline, according to research by the University of Helsinki. The species, once widespread, has seen its population collapse by 70–80% since 1980, with the last confirmed nesting in Kanta-Häme recorded in 2011.

Acoustic monitoring using AI-assisted recorders has detected only a handful of individuals this year—down from just 2–3 owls logged in over 8,000 hours of audio last spring. Researchers warn that without large, protected forest areas, the species may disappear entirely from southern Finland.

AI reveals owl “accents” tied to vanishing habitats

Hanna Rosti, a researcher at the University of Helsinki’s Lammi Biological Station, has deployed dozens of acoustic recorders in Kanta-Häme’s forests, capturing sounds from 7 PM to 9 AM—peak owl activity hours. While AI helps analyze the data, each potential boreal owl call is manually verified.

The recordings reveal striking regional variations in the owls’ calls, akin to human dialects. Finnish boreal owls “puput” (hoot) differently from their Swedish relatives, with distinct rhythms and pitches. “They’re like rock stars marking territory—I’m here, this is mine,” Rosti describes. But as southern Finland’s old-growth forests vanish, so does this local vocal identity.

Logging and predators push owls to the brink

Birdwatcher Markku Hyvärinen, who has monitored forests since the 1960s, calls the boreal owl the “spirit of the forest.” He traces its decline to the loss of mature spruce-dominated woods—prime nesting sites that are also lucrative for timber harvesting. “The boundary now runs roughly from Tampere southward. Below that, it’s a void,” he says.

Small owls face additional threats during migrations between forest patches, where larger predators like the pygmy owl and northern goshawk prey on them. Rosti’s findings suggest that even light conservation measures fall short: “We need expansive protected areas—not just scattered patches.”

This year’s surveys in Kanta-Häme turned up just one boreal owl, a stark contrast to the 45 hours of calls recorded in early 2025. Without urgent habitat protection, researchers fear the species’ southern Finnish dialect—and the owls themselves—could be silenced permanently.