ShareThis Page

Ash borer invasion good for woodpeckers, nuthatches, both natural insect predators

| Thursday, Aug. 15, 2013, 9:40 p.m.
Jason Cato | Tribune-Review
Woodpeckers damaged this dead ash tree in Schenley Park looking for emerald ash borers and their larvae. The invasive insects feed on ash trees, killing them in the process.
Jason Cato | Tribune-Review
Two runners pass beneath dead ash trees in Oakland’s Schenley Park this week. The emerald ash borer will eventually kill nearly all of the ash trees in North America, including the 60,000 in Pittsburgh parks and 300 million across Pennsylvania. Scientists have discovered certain woodpeckers and nuthatches are experiencing population booms around Detroit and southeastern Michigan, where the infestation was discovered in 2002. They expect the same could happen in Western Pennsylvania.

In the bug-eat-wood world that is ridding the country of its ash trees, scientists have learned that some bird species are thriving by feasting on the invaders.

The populations of red-bellied woodpeckers and white-breasted nuthatches, both natural insect predators, soared in the Detroit area, ground zero of the emerald ash borer invasion, research by Cornell University and the U.S. Forest Service found.

Scientists discovered the destructive beetle's presence in southeastern Michigan in 2002. Five years later, the voracious green beetle arrived in Cranberry.

“It's pretty horrific, really,” said Andrew Liebhold, an entomologist with the Forest Service in Morgantown, W.Va., and co-author of the study. “In the Pittsburgh metro area, it is about 10 to 15 years behind Detroit. The worst is yet to come.”

The region's woodpecker and nuthatch populations could surge, he said.

“It's probably affecting a whole slew of other organisms, but people count birds, so we can track it,” Liebhold said. “People don't really count the number of millipedes in their backyard.”

While researchers focused on the Detroit area, Pittsburgh served as one of five control sites across the Midwest.

In addition to gains in the numbers of the red-bellied woodpecker and white-breasted nuthatch, downy and hairy woodpecker species initially saw population declines after the emerald ash borer's appearance but have rebounded in recent years.

All four bird species noted in the study live in Western Pennsylvania.

The impact woodpeckers have had on ash trees in city parks caught Phil Gruszka's attention. He's director of parks management and maintenance policies for the Pittsburgh Parks Conservancy.

“We can tell there are more woodpeckers in the parks,” he said. “You see the bark off all the trees.”

Signs of an ash tree infested with emerald ash borers are stripped bark and woodpecker markings, Gruszka said.

Pittsburgh's public parks contain about 60,000 ash trees. Pennsylvania is home to 300 million, according to the state Department of Conservation and Natural Resources.

The emerald ash borer will kill nearly all of them, as North American ash trees have no natural resistance to the insects.

“But the tree species isn't going to go extinct,” Liebhold said.

Emerald ash borer larvae eat tunnels into the wood, destroying a tree's water and nutrient system and its ability to feed itself.

The emerald ash borer likely arrived in the United States in the late 1980s, Liebhold said. It originated in Asia. More than a decade passed before its damage became apparent.

“If it had been discovered five years earlier, it probably could have been eradicated,” Liebhold said.

The woodpeckers don't mind. They peck away the bark to get to the insects and others that move in once the tree dies.

Red-bellied woodpeckers and the nuthatch likely discovered the new food source first, with competition causing the short dip in the other woodpecker species, researchers concluded.

That the birds would thrive from the new food source and nesting areas in dead ash trees makes sense, said Bob Mulvihill, an ornithologist at the National Aviary in the North Side.

“It becomes a smorgasbord of grubs and other insects,” he said. “Birds really are opportunistic. They will begin to work those trees over.”

Jason Cato is a staff writer for Trib Total Media. He can be reached at 412-320-7936 or

TribLIVE commenting policy

You are solely responsible for your comments and by using you agree to our Terms of Service.

We moderate comments. Our goal is to provide substantive commentary for a general readership. By screening submissions, we provide a space where readers can share intelligent and informed commentary that enhances the quality of our news and information.

While most comments will be posted if they are on-topic and not abusive, moderating decisions are subjective. We will make them as carefully and consistently as we can. Because of the volume of reader comments, we cannot review individual moderation decisions with readers.

We value thoughtful comments representing a range of views that make their point quickly and politely. We make an effort to protect discussions from repeated comments either by the same reader or different readers

We follow the same standards for taste as the daily newspaper. A few things we won't tolerate: personal attacks, obscenity, vulgarity, profanity (including expletives and letters followed by dashes), commercial promotion, impersonations, incoherence, proselytizing and SHOUTING. Don't include URLs to Web sites.

We do not edit comments. They are either approved or deleted. We reserve the right to edit a comment that is quoted or excerpted in an article. In this case, we may fix spelling and punctuation.

We welcome strong opinions and criticism of our work, but we don't want comments to become bogged down with discussions of our policies and we will moderate accordingly.

We appreciate it when readers and people quoted in articles or blog posts point out errors of fact or emphasis and will investigate all assertions. But these suggestions should be sent via e-mail. To avoid distracting other readers, we won't publish comments that suggest a correction. Instead, corrections will be made in a blog post or in an article.