Environment & Science
5:29 pm
Mon August 12, 2013

Woodpeckers and nuthatches benefit in ash borer's wake

Red-bellied woodpeckers and white-breasted nuthatches, to be specific.

Scientists say the two bird species thrived when the emerald ash borer moved in. The invasive insect wiped out tens of millions of ash trees around the region.

The researchers compared four bird populations in the outbreak’s epicenter in southeastern Michigan (near the Detroit Metro Airport), to the populations outside just of the epicenter and with five other cities in the region (Cincinnati, Cleveland, Columbus, Indianapolis, and Pittsburgh).

The scientists used data gather by citizens from the Cornell Lab of Ornithology's Project Feeder Watch.

They found that populations of  the red-bellied woodpecker started increasing in 2006 --

Female red-bellied woodpecker.
Credit @maia bird / Cornell

and populations of the white-breasted nuthatch started going up in 2005 ---

Female white-breasted nuthatch.
Credit Matt MacGillivray / Flickr

The emerald ash borer was first discovered near Detroit in the summer of 2002. Scientists suspect the invasive ash borer came in on wood packing crates shipped from overseas in the early 1990s or late 1980s.

Andrew Liebhold is an entomologist with the U.S. Forest Service, and he co-authored the study published in the Journal Biological Invasions.

“I suppose the upside of the whole thing is that dead and dying trees are a good thing for woodpeckers and actually quite a few birds use dead trees as nesting sites,” said Leibhold.

Liebhold says it's likely that the birds' babies survive better with the abundant food source, and that the parents have more than one clutch per season.

The research also found that two other woodpecker species didn't fare as well initially.

The downy woodpecker --

Male downey woodpecker.
Credit user vidular / Flickr

and the hairy woodpecker.

Female hairy woodpecker.
Credit user ronalduk / Flickr

From their report:

Thus, the response of these four species to the EAB invasion was surprising to the extent that only two of the species exhibited clear increases while the other two apparently suffered decreases, at least initially. Such variability is perhaps to be expected given the many routes, both direct and indirect, that an invasive such as EAB can influence predator populations.

 “Some species are better than others in utilizing novel food resources, and so it’s quite possible that the red-bellied is able to handle this new food resource and take advantage of it,” said Leibhold. But even though the birds feed on the insects, it's not likely they'll stop emerald ash borer populations from wiping out ash trees across the U.S. From Keith Matheny of the Detroit Free Press

Earlier research shows woodpeckers will eat up to 40% of emerald ash borer larvae and pupae in an area. But more woodpeckers may only slow, and can’t stop, what appears coming — the eradication of ash trees in the U.S., [Andrew Liebhold] said.