From Woodpeckers to Mosquitoes

First posted on 06-23-2011

When I moved to Arkansas some years ago, I worked the four to twelve shift in a factory in town and attended classes at the university during the day. Sleep was at a premium for me, but a pileated woodpecker decided I needed to rise just before dawn.

He liked the looks of my bedroom window and woke me for weeks at about five thirty in the morning. His attempts at drilling through the glass bounced annoying sound waves off my walls. Apparently, he saw the reflection of a tree but assumed it was the real thing.

I gave up any plans I may have hatched for his demise after learning the creature was a protected species. Eventually, the woodpecker gave up either because of frustration or because of fright from witnessing my bizarre morning hair after a fitful sleep.

I didn’t know it then, but woodpeckers do far more than harass night shift workers. They actually benefit songbirds that occupy woodpecker holes for safety and for nesting. Bluebirds, for one, do not have the means to construct nesting cavities themselves and rely on woodpecker holes, decaying trees or human-built boxes for shelter.

According to a recent study led by Kathy Martin at the University of British Columbia, over a thousand different species of birds and mammals rely on holes in trees for nesting and living spaces. Mammals who like the safe environment provided by tree holes include squirrels, flying squirrels and, in big holes, oppossums. These animals find they can sleep a little easier inside a tree than exposed on a branch or on the ground.

The holes aren’t simply used once and discarded. “Some of the tree cavities in Canada were used 17 times in 13 years by up to five different species,” says Martin. “One tree cavity can sustain a lot of wildlife over its lifetime.”

Martin and her team discovered that on most of the world’s continents, over 75 percent of the holes used for shelter by animals were caused by decay.

“When wildlife depends on decay-formed cavities, they are relying on large living trees,” Martin said. “Most trees have to be more than 100 years old before decay cavities begin to form and often several centuries old before large cavities or many cavities develop in one tree.”

But in our neck of the woods—North America—things are drastically different. Martin said that woodpeckers are accountable for almost 99 percent of the tree cavities used by birds and mammals.

Which is one of the reasons my old pileated woodpecker friend and many woodpecker species are protected. Their disappearance would have a ripple effect throughout the forest, causing the decline of other species and disrupting the balance of nature. No woodpeckers, less birds. Fewer birds, more mosquitoes. A disturbing picture.

So why the discrepancy between North American birds and the rest of the world? Martin’s team noted that woodpeckers make perfectly good holes in trees all over the world, but in places like Argentina, those holes only lasted about two years before they healed over. But those produced from a tree in decay lasted for for 25 years or more.

In parts of Europe, the difference was less dramatic. Woodpeckers produced holes that lasted for six years compared to decay-induced holes that made it for 13 years. On the North American continent, both types of holes lasted the same length of time, about 14 years.

That makes me wonder if a cleanly bored woodpecker cavity is preferred over a decaying nightmare of a home when given a choice. Whether it is or not, Martin feels that agencies overseeing the world’s forests should take note.

“Most forest policies help protect younger trees but promote the harvest of older, larger, living trees—the very trees needed by cavity-nesting animals,” says Martin.

In the years that have transpired since my first encounter with a hungry pileated woodpecker, I’ve learned to appreciate the species a little more. I enjoy their wild cackles when I walk through the woods, although I can’t promise I wouldn’t dream up ways to defeat one if my bedroom window should get attacked again. But I wouldn’t want to be responsible for a ripple that ended up causing me to donate blood to a mosquito’s cause. Maybe I’ll just invest in ear muffs.