Ancient forests can help songbirds cope with global warming: NPR

Each spring, songbirds migrate for thousands of miles to breed in the Cascade Mountains of Oregon. At the bottom of a forest, Hankyu Kim, a researcher at Oregon State University, has the feeling that he has entered the head of a species, the Hermit Warbler.

"These birds are territorial in the breeding area, they have created their territory and are fighting to defend it," he said.

Armed with this knowledge, an almost invisible net is threaded between two recycled fishing rods, a plastic lure and a looping record of bird songs, Kim's trap is set.

Its yellow helmet matches the yellow head of the Hermit Warbler, which at any time descends from the treetops to look for the origin of the song. Kim hides in the bushes, trying to follow the frantic bird with binoculars.

"When the birds arrive, they hit the net, fall into a pocket and lie there like a hammock," says Kim.

And in just a few minutes, the Hermit Warbler bites on the hook, flies over a small clearing and hits the net.

It's another win for the lure.

Kim and her colleagues develop a new experience, trying to follow the movements of hermit warblers through the forest. Learning how they move could help explain how bird species are managing rising temperatures and climate change.

"We have these long-term population monitoring routes in the Northwest, and a surprising number of species are in decline," said Matt Betts, a professor at Oregon State. "In fact, more than half of the species living in a forest like this are in decline."

Rising temperatures may decrease where some birds can live and where they can find food.

For the Hermit Crab Warbler, these decreases reach 4% per year.

Research conducted by Betts and Sarah Frey, in the state of Oregon, found that warblers had declined in areas of young forests, including those replanted after clear-cutting. But the hermit warblers are doing better in other areas.

"In landscapes where forests were older, the decline in their population was reduced or even reversed, even as the climate warmed," said Frey.

The Pacific Northwest has been striving for decades to preserve its ancient forests and warblers thrive there. This suggests that these forests have somehow protected them from the adverse effects of rising temperatures.

The question is why and this is where this new study comes in.

Kim and fellow researcher in the state of Oregon, Adam Hadley, spread the feathers of the imprisoned hermit's warbler and secure a radio tag on his back using non-toxic glue (of the type used for false eyelashes). Then they release the bird and it flies away.

The next day is the real test.

Hadley and the others grow in a dense stand of trees, equipped with receivers that look like old-fashioned television antennas.

"He's off," Hadley said, holding the antenna over his head.

"We'll try to be as quiet as possible," says Betts, while the branches break underfoot.

They walk in a drainage network of a 50-year-old tree plantation, remnant of the forest past of the H.J. Andrews Experimental Forest. They then go to a grove of much older trees, some of which are nearly 300 years old.

Hadley explains that temperatures can be different at different heights of a tree. "It's possible that when it's hot, [songbirds] "Maybe use only the lowest and shaded parts of the trees," he says, which he assumes they can climb higher when it's cooler.

He says that the complex layers and pure biomass of old vegetation keep the temperature in these forests up to 5 degrees lower. But researchers can not fully understand what is happening without knowing more about how birds use forests.

Hadley put the antenna in the air trying to locate the location of the warbler. "I do not get the most powerful signal at the top of the tree, it seems to be a little stronger in the middle of the copy," he tells Betts.

He and the others will compare the movements of the Hermit Warblers to the temperature data they also collected. They hope to take a step closer to understanding how this species of native songbird could cope with global warming.

"I do not see the likelihood that Hermit Warblers will have air conditioning in the near future," said Betts.

Old growth might be the best solution.