Old-Growth Forests Could Shield Songbird Populations From Effects Of Climate Change, Researchers Say

A yellow-capped bird rests on a branch.
Frode Jacobsen / Wikimedia Commons/Cropped and Resized (CC BY-SA 2.0)

New research suggests that old-growth forests could be instrumental in helping warblers — and other songbirds — survive the rising temperatures brought about by climate change.

According to NPR, a team of researchers from Oregon State University has been monitoring the behavior of hermit warblers in the forests of the Pacific Northwest, in hopes of finding out how the birds are responding to progressively warming temperatures. Oregon State professor Matt Betts explained that the research is important because a “surprising” number of songbird species are seeing their populations decline, with the declines being as high as 4 percent per year for the hermit warbler population.

“Actually, more than about half of the species that live in a forest like this are in decline,” Betts told NPR.

While hermit warbler populations had taken an especially significant hit in younger forests — including those that were replanted to replace trees cut down by loggers — the researchers discovered that the birds thrived in older forests, where population declines didn’t just slow down, but were also reversed in some cases. This trend in old-growth forests was evident even if the climate continued to warm, observed Betts’ fellow OSU researcher, Sarah Frey.

In an effort to determine why hermit warblers were shielded from the effects of climate change when they migrated to old-growth forests, OSU researchers Hankyu Kim and Adam Hadley conducted an experiment at the H.J. Andrews Experimental Forest in Oregon. There, they placed radio tags on the feathers of trapped birds, then checked back on them the next day as they followed them to a grove of older trees — including some that were estimated to be close to 300-years-old.

Old-growth forests in Olympic National Park, Washington
  Jim Schwabel / Shutterstock

Explaining what he and his colleagues had discovered through their experiment, Hadley said that the warblers appear to stay in different parts of the trees depending on the temperature. At the time that the researchers were tracking the birds, they received the strongest signals in the mid-canopy area, with signals at the top being substantially weaker.

“It’s possible that when it’s warmer, [songbirds] may be only using the bottom and more shady parts of the trees,” said Hadley, adding that it’s possible that the birds fly to the higher parts of the tree when the weather cools down.

At this point more research is needed as the OSU team continues to work out why songbirds thrive in old-growth forests. According to NPR, the researchers are planning to “get another step closer” by seeing if there are any noteworthy links between the hermit warblers’ movements and temperature changes in the area.