Mountain Owls Mystery Unveiled: Tracking the Elusive Night Raptors in the Alps

This feature is part of our series “The Naturalist’s Walk”: a hike that explores a unique species or habitat, accompanied by a passionate expert.

Belledonne Massif (Isère), report

The location of our report is kept confidential. A mixed forest of conifers and deciduous trees somewhere in the Belledonne range, north of Grenoble. Our guide for the day, Pierre Pola, prefers to be vague about the specifics of his annual route to count the population of Eurasian pygmy owls and boreal owls. He is cautious not to spark public interest that could disturb these small mountain raptors, remnants of the Ice Age and now protected species.

With its golden-yellow eyes topped with white eyebrows, a white-speckled brown plumage, and a golden beak, the Eurasian pygmy owl is a tiny raptor, just 16 centimeters tall. It is highly territorial, unlike its relative, the boreal owl, which is slightly larger with dark brown plumage dotted with white and has been found up to 1,200 kilometers away from the Alps.

Pierre Pola has been a forester at the National Forest Office (ONF) for about forty years and is also a member of the National Unified Union of Forestry and Natural Space Workers-Solidaries. A trained ornithologist, he has been conducting these surveys since 2017 with the goal of gaining better understanding of these species to adjust forestry practices for their conservation.

His method is detailed, with five observation points for each owl species: the Eurasian pygmy owl in the late afternoon and the boreal owl at dusk. The first step is active listening: Pierre Pola and his intern, Lara Figuet, pause and try to discern the owl’s call for two minutes. They then play a recording of the owl’s call before listening intently again for five minutes, hoping to hear a hoot.

This technique helps estimate the number of individuals within a given area. In the 2,000 hectares of public forest that Pierre Pola oversees, there are estimated to be five to seven pairs of Eurasian pygmy owls and five pairs of boreal owls. Although not comprehensive, this count provides a demographic trend. This year, for example, Pierre Pola noted the absence of the boreal owl’s call, possibly due to a fluctuating rodent population, its preferred food, which varies annually in the area.

The first listening point is beside a forest trail. Pierre Pola plays the first recording for the Eurasian pygmy owl. A chorus of songbirds responds. Initially, the crested tit whose call sounds like a car failing to start, followed by the wood nuthatch, the peony bullfinch, the crested tit, and a wren. A cacophony known as “mobbing,” where small birds warn the group of a predator’s presence, in this case, the owl. “If they locate it, they may gather to harass it. It’s a remarkable show of interspecies solidarity,” smiles Pierre Pola.

However, this evening, despite our attentive listening, no melodic whistling is heard. To increase our chances, we move silently to the second listening point, alert to any sound in the branches. “You have to watch the treetops carefully. Sometimes, she perches silently and just watches us,” says Pierre Pola.

Neither the Eurasian pygmy owl nor the boreal owl is particularly shy. The forester recalls a nest near a hiking trail frequented by schoolchildren on field trips. “The female nested just 10 meters off the path for two years. But I think by the third season, she had moved on.”

At the second listening post, the same protocol yields no sight of the Eurasian pygmy owl. The playback only triggers the calls of a song thrush, a goldcrest, a coal tit, and a chaffinch “singing the song of rain,” as Pierre Pola poetically describes.

Approaching the third listening station, a series of rapid “tic-tic-tic” sounds fill the air. It’s the noise of a great spotted woodpecker marking its territory while signaling to females. This climbing bird is also a nest builder, using its sharp beak to carve out homes in trunks—a nest it abandons after its first brood, which then benefits other forest dwellers like the owls.

Further on, Pierre Pola points out a spruce with peeling bark. “I saw a male Eurasian pygmy owl circling it three weeks ago. I know there’s an intent to settle.” We stop and listen. Only silence greets us. Pierre Pola thinks the female might be incubating her eggs. To leave her undisturbed, he chooses not to play the recording.

The selected nesting site for this Eurasian pygmy owl is a conifer decimated by bark beetles, tiny beetles that bore tunnels under the bark, disrupting the flow of sap. To prevent their spread, all affected trees are cut down and the dead wood is cleared. A practice that displeases the forester. “By cutting them down, we not only prevent the beetle’s predators from settling in, but we also deprive other fauna of refuge. Moreover, this dead wood feeds the biomass power plants. Yet, in winter, 97% of the food consisting of xylophagous insects is found within it. It is essential for the life of all organisms in the forest.”

Pierre Pola advocates for a moratorium on cutting from February 1 to July 15, during the nesting period. However, the Bird Protection League has yet to address the issue. While the ONF is beginning to consider the idea, it faces the commercial reality of the agency, which needs to be profitable today.

“It’s all about making numbers. We’ll mobilize loggers, machines, boost the economy. But we’ll have destroyed a large part of the forest ecosystem. The entire living world is affected by the radicalization of forestry,” laments Pierre Pola. Thus, the greatest threat to these little mountain owls is not—yet—climate change, but the industrialization of the forest, which destroys their habitat.

As we reach the last listening post, the night falls along with the rain. The birds have quieted, and the Eurasian pygmy owl remains silent. As for the boreal owl, there’s no point in trying to hear it: the bad weather has ended the forester’s protocol. Pierre Pola will have to return to attempt once more to hear the calls of these rare and delicate raptors.