Recent news coverage has suggested a spike in pileated woodpecker sightings in Chicago's western suburbs may be tied to the ongoing destruction of ash trees by the emerald ash borer, an invasive beetle native to Asia. But according to at least two wildlife experts, it probably has more to do with the restoration of local habitat.
The pileated woodpecker favors dead or dying trees as places to nest or find food, like emerald ash borer larvae or carpenter ants.
But ecologist Brian Kraskiewicz of the Forest Preserve District of DuPage County thinks drawing a correlation between the pileated woodpecker and the emerald ash borer invasion is a bit of a stretch.
“It’s exciting that this species that used to be relatively rare is starting to become more visible in DuPage County,” Kraskiewicz said. “But I think it’s due to the restoration work we’ve been doing for the past 10 years and not necessarily the emerald ash borer.”
Kraskiewicz said invasive plants like honeysuckle and buckthorn are removed to restore woodlands, where he said a number of pileated woodpecker sightings have been. That brush and shrubbery, which should not be growing in the native ecosystem, would otherwise make it difficult for pileated woodpeckers to fly around or reach the forest floor to forage. He said sightings in DuPage County have in fact been on the rise since the early 2000s, long before the emerald ash borer was discovered in DuPage County in 2007.
Thomas Barnes, program associate for the Bird-Friendly Communities program at the Audubon Chicago region, agrees with Kraskiewicz and thinks better management by forest preserves to support large, contiguous tracts of woodlands is helping this woodpecker species to thrive, not the destruction caused by the emerald ash borer. After all, pileated woodpeckers like plenty of space.
“Pileated woodpeckers are very territorial,” Barnes said. “Two birds will take up and live in a specific, large area for quite some time. The pecking against wood, or drumming, they do is not only to get food but it’s a territorial call and will tell other pielated woodpeckers to stay away.”
The colorful bird is the largest woodpecker species found in Illinois, although it’s rarely spotted in or around urban areas due to its preference for heavily wooded forests with mature trees.
The online database eBird, which collects data from professional and amateur birdwatchers, shows that all of the 2016 pileated woodpecker sightings they've collected have so far occurred in woodlands outside city limits. The map shows this year’s closest sighting to Chicago was at Salt Creek Woods, about 15 miles west of the city.
Adult emerald ash borers, which are about a half-inch long, lay eggs on ash tree species like the white ash and green ash trees commonly found in Illinois. Larvae then tunnel through the tree, feeding on its inner bark, which disrupts the flow of water and nutrients, killing the tree.
Millions of ash trees have been wiped out by the wood-boring pest since it was discovered in Illinois nearly a decade ago. Last year, state officials hoping to prevent the emerald ash borer’s spread “threw in the towel” by lifting a quarantine on moving non-coniferous, cut firewood.
And while it's seemingly good news that the pileated woodpecker, along with other woodpecker species, eat emerald ash borer larvae, Kraskiewicz said woodpeckers are probably not a worthy contender for the as-yet-unstoppable beetle.
“There are probably too many emerald ash borers out there for the woodpeckers to handle,” Kraskiewicz said. “They might slow them down slightly, but I don’t think they’ll stop or eradicate emerald ash borers.”
The U.S. Forest Service is experimenting with different biocontrol agents, like wasp species that eat emerald ash borer larvae and eggs.
The bright side of the emerald ash borer dilemma, if there is one, is that dead ash trees will inevitably serve as a food source and nesting habitat for woodpeckers and other animals, like bats, squirrels and raccoons.
And, as Kraskiewicz put it, the pileated woodpeckers are “making the best of a bad situation.”
Follow Evan Garcia on Twitter: @EvanRGarcia
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August 19, 2014: We see how the city is taking care of Ash trees hit by the Emerald Ash borer.