Recently I heard from a colleague down in Madison who read my column about the apparent woodpecker assault on my oak tree. Andrea Diss-Torrance is the Invasive Forest Insect Program Coordinator with the Public Lands and Conservation Services Section of the DNR Forestry Bureau. She surmised from my column that the guilty party was most likely a pileated woodpecker, and it was probably after carpenter ants, a delicacy to these birds. This makes sense; the damage looks a lot like how a bear shreds a log lying on the ground. Once they get into the wood, the ants grab their larvae and try to escape. Time is of the essence; you have to really throw some chips to get as many ants and larvae as you can.
It happens occasionally that someone comes to my office and blames a woodpecker for killing their tree. In fact, it is most likely that insects killed the tree, and the woodpecker was there to eat the perpetrators. Andrea Diss-Torrance sent me some great information about the value of woodpeckers. Here are some of her quotes:
“One of the most reliable indications of emerald ash borer (EAB) infesting an ash is when woodpeckers flick the bark off an ash during winter going after the larvae. This indication of infestation is very helpful because it flags a tree that is likely to become a hazard soon. Community foresters and DNR parks managers use woodpeckers as an early warning system to prioritize ash trees for removal before they can fall on someone. Woodpeckers are one of the most important biological control methods of EAB in North America and the most important native predator. They have been observed to remove up to 95 percent of EAB larvae in some trees.”
We are on the watch for EAB up here, and have implemented firewood regulations to try to control the spread.
“Woodpeckers prefer to forage on dead or dying trees, especially in the winter as these trees are the ones with the highest populations of woodborers in them. This is helpful as it lowers the number of adult pests that will emerge from these trees in the spring to mate and lay the next generation of eggs.”
She further explains, “Many bird and mammal species nest or shelter in cavities woodpeckers have made and used for nesting. Bluebirds, chickadees, wrens, some warblers, nuthatches, tree swallows, swifts, screech and barred owls, wood ducks and hooded mergansers, as well as bats, squirrels, deer mice and pine martens are among species that depend on woodpeckers to make the comfy cavities for their use once the woodpecker has finished nesting in it.”
I couldn’t agree more; in college, we studied a forest transect and found a great majority of the tree-nesting wildlife species observed used holes excavated by woodpeckers on the south and east faces of trees.
Here in the Northwoods, we have a good number of woodpecker species. Two species of special concern, the red-headed and black-backed woodpeckers, are few in number. We have a good number of downy, hairy and pileated woodpeckers here. We also have Northern flickers and yellow-bellied sapsuckers, which are kinds of woodpeckers as well. Andrea says, “Sapsuckers may drill shallow holes in trees (look for orderly rows of small holes) to lap up the sweet sap that oozes out. This damage is tiny, though, and typically well tolerated by a tree.”
Do we have any other creatures that gobble up tree sap? Squirrels and humans come to mind! In fact, people regularly tap maples, collecting gallons of sap per tree with no effect on the health of these trees.
So, woodpeckers are truly friends of the forest, not fiends. They serve an important ecological function, and there is room for them in a healthy forested landscape.
Jeremy Holtz is a wildlife biologist with the Wisconsin DNR and writes a weekly column in the Star Journal.To contact him, call (715) 365-8999.