Science Snapshot · 3-minute read
The paper: Borowski Z, Bartoń KA (2025). Avian predation has the strongest impact on vole survival during winter and spring in temperate grasslands. Scientific Reports 16: 561.
In one sentence: When researchers kept birds of prey away from wild voles in Poland, more voles survived the winter and spring, but by summer vole numbers were about the same as in open plots.
Why it matters here
At the first Vole Summit, growers named “predators and wildlife habitat” as one of four research priorities. Most evidence on birds of prey and voles comes from the far north. This is one of the few experiments from a temperate grassland.
Three take-homes
1. Birds take a real share of voles. From November to March, monthly vole survival was 15–22% lower in open plots than in plots where birds were kept out. At the late-winter peak, birds accounted for an estimated 44% of vole deaths. That estimate is uncertain, with a range of 19% to 72%.
2. Winter and spring are when birds matter most. Cover is thinnest then, so voles are easier to find. Once vegetation thickened in summer, it hid voles from birds.
3. Birds alone did not hold vole numbers down. Netted plots had more voles from March to May. By summer the difference had faded at two of the three sites. It lasted only at the site closest to a forest edge.
What they did
Where: wet sedge meadows in Biebrza National Park, north-east Poland, from November 2005 to November 2006.
Voles: root voles, a wild relative of our gray-tailed vole.
The experiment: three pairs of plots, each 50 m by 50 m. One plot in each pair was covered with netting 1.5 m above the ground. This kept birds out but let foxes, weasels and stoats in.
Tracking: live-trapping every two months, with 3,984 captures of 1,731 marked voles.
The birds: buzzards, harriers and three kinds of owl.
What it means for the Willamette Valley
Predators belong in the toolbox, but they are not the whole answer. Birds removed a meaningful share of voles here and still did not stop numbers rising in spring.
The timing lines up. Birds had their biggest effect in winter and early spring. That is also when speakers at the 2026 Vole Summit recommended control: when populations are low and before the grass is tall.
Cover protects voles. Tall, dense vegetation hid voles from birds in this study.
Trees and perches nearby may matter. The effect was strongest at the plot 300 m from a forest edge, compared with 900 m at the other two. The authors put this down to woodland owls and perching sites. The study did not test perches or nest boxes.
We are looking at predators too. Camera traps for predators are planned at our long-term monitoring sites.
Keep in mind
One year and three pairs of plots. This is a small experiment.
A different vole in a different place. These were root voles in a wetland with snow on the ground from December to March. Willamette Valley winters are mild and wet.
A peak year. The study ran while voles were at the top of their cycle. The authors expect birds to matter more when vole numbers are falling.
Possibly an underestimate. Voles living at the edge of a netted plot could still wander out from under the net.
Old fieldwork. The data were collected in 2005–06 and published in 2025.
Read the paper
https://doi.org/10.1038/s41598-025-30214-y (open access)
