QUECHEE – Rehabilitators at the Vermont Institute of Natural Science are used to seeing injured barred owls arriving for treatment. After all, raptors are abundant and are not afraid of people. But in some years the number of barred owl entries doubles, and many arrive half-hungry.
“Some are just skeletons with next to nothing of them,” said Bren Lundborg, wildlife protection officer at VINS. In the winter of 2019-2020, nearly a third of barred owls brought to the VINS clinic arrived emaciated, he said.
Naturalists had a hypothesis: in winter, barred owls hunt with their ears, jumping to attention when they hear a rodent rummaging under the surface of the snow. Then, they dive into the hidden prey and capture their food. But in hot, humid winters, a thick layer of ice covers the snow and could put owls out of reach of their food.
In search of a definitive answer, wildlife rehabilitators at the Quechee Nature Center have teamed up with Mike Anderson, a so-called “digitizer” at SAS Institute, an analysis software company. He became a lifelong raptor enthusiast when he read My side of the mountain, an adventure novel about a boy and his peregrine falcon.
He used 18 years of weather data from Killington Ski Resort and VINS records to paint a picture of what a bad year looked like for owls. His findings, which they hope to publish as a research paper, confirmed the hypothesis.
In a bad winter for the barred owl, temperatures have never dropped as low as in other years, instead approaching the freezing point. It snowed at the start of the year, but it rained more than usual, so the ice formed into a thick crust on the snow.
Under these conditions, the barred owl catch was “almost double the baseline,” Anderson said. Weakened by starvation, barred owls struggle to recover from their injuries, compete with other predators, and repel disease. They also reproduce less well, and young barred owls, not used to hunting for themselves, suffer the most. Other species of owls, such as great gray owls, which also dive in the snow to hunt can also suffer, he said.
A bad year for barred owls takes its toll on humans. Brown and white striated raptors are adaptable. They don’t hesitate to hunt near people and learn to hunt in a man-made landscape, Lundborg said. And when they are desperate, they can be aggressive.
“Last winter they were hunting in bird feeders when food was scarce,” Lundborg said. There, they could pursue rodents who collect the fallen seeds.
One was so desperate that he attacked a chicken right in front of a person. At 1.5 to 2 pounds, they’re too small to threaten most pets, he said. But despair also takes other forms. VINS treated another barred owl whose stomach was filled with caterpillar exoskeletons that she had eaten when she could find nothing else.
Climate change is likely to make winter conditions that lead to starvation for barred owls more frequent, VINS employees said.
“Forecasted changes in regional weather conditions in Vermont and New England predict that the frequency of undernourished barred owls will only increase over the next 20 to 30 years as we continue to see unusually winters. wet, ”Anna Morris, senior wildlife educator at VINS, said during a presentation on the topic last year. “This study shows another way in which climate change is currently affecting the health of wildlife around us,” she added.
Yet barred owls are not threatened with extinction. Their population is increasing every year as more forests grow back and age in the region, Lundborg said. They thrive in old growth forests where they can nest in the hollows of old, gnarled dead trees.
But barred owls aren’t the only species to contend with a changing winter climate to which they haven’t adapted.
Data from the Environmental Protection Agency shows that more and more birds have altered their migration patterns. Between mid-December and early January, 305 widely distributed bird species in North America moved 40 miles north, with some moving north up to 200 miles. And birds aren’t the only animals moving north: Parasites that carry new diseases, like avian malaria that now spreads among loons, pose new threats to New England birds.
Loons that spend their summers in New England also linger longer when temperatures slowly drop, Lundborg said. But they need a large body of open water to take flight. So if the ice forms quickly, it can trap them in a small area of open water with no way to escape.
Claire Potter is a member of the Report for America Corps. She can be reached at firstname.lastname@example.org or 603-727-3242.