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Birds:Movements from bird counts reveal climate-change effects

Published January 12. 2013 09:06AM

The Audubon Society has just completed its 2012 Christmas Bird Count, and for Rob Bergstresser, a volunteer avian biologist at the Carbon County Environmental Education Center, the data both locally and nationwide is providing a confirmation that our climate is warming.

"This is almost certainly the most comprehensive analysis of bird movements over the past 40 years and what they reveal about the effects of climate change," noted the Audubon Society website. "It tells us that those who think climate change will be felt far from home and far off in the future had better think again. Its impacts are being seen here and now..."

Locally, Bergstresser worked with about two dozen volunteers to count birds within a 15-mile-radius circle about a convenient central point on Route 209 between Coaldale and Tamaqua. The volunteers divided the circle into 11 zones, and on December 28, for as many hours as they could within the 24 hour period, they counted birds.

Bergstresser's zone included the west side of Mauch Chunk Lake Park and the Carbon County Environmental Education Center. He walked, he listened, he watched for movement, and he searched the pine trees and spruces where birds might be feeding on cones.

He saw a variety of birds, the most surprising being the Northern Shrike, "a very uncommon bird for this area," Bergstresser noted. "They are only here in the wintertime. It's a bird that breeds in the Arctic and the tundra arboreal regions of Canada. They routinely move south to find better weather to hunt prey."

Contrary to what many people believe, birds do not migrate to get away from cold weather. They migrate to find food. "If there was a possibility of insects flying around here in the winter, the warblers wouldn't move south at all. It's all about finding a food source."

Bergstresser has been noting that on average, locally the birds are migrating to areas at least 50 miles and as much as 200 miles to the north of their traditional winter habitats, while the Audubon Bird Count has documented some birds migrating over 400 miles north of where they wintered in 1966.

Some birds are not migrating it all. "We are seeing a more species that should be further south, like in southern Pennsylvania," Bergstresser said. "We are seeing them around Carbon, Schuylkill, and Luzerne Counties.

"I saw red-winged blackbirds at Mauch Chunk Lake," Bergstresser said. "That's a bird that we never saw in the wintertime. They tend to move south by early November. So to see one in January at Mauch Chunk Lake is rare. To see one in Quakertown may not be so uncommon. "

Red-winged blackbirds glean the remains after corn and grain harvests. When the fields become covered with snow, these birds are stranded in the north without a food supply. Last year, Northeastern Pennsylvania didn't have much snow, and the birds that survived lost their incentive to migrate this year. This year, we have had good snow cover, and so the birds will find it more difficult to survive and will tend to be found at bird feeders.

"Birds are an early indicator species," Bergstresser explained. "They are very sensitive to changes in the environment, whether it is natural or human caused. If we see populations start to die off. That's a red flag immediately, so we want to see what's going on."

"Birds are very selective in their habitat. Many birds will nest and feed in only one habitat. If real estate expands onto their habitat, either they're not going to make it or they move to another area. They have wings."

Asked, "Is the bird to the environment what the canary used to be to the mine?"

"Absolutely," Bergstresser said. "That's a perfect example. They are a serious indicator species for the environment. You need to pay close attention to them."

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