My little log cabin north of Fairbanks sits on the lower slopes of a forested hillside above a small creek. Out my office window are some scraggly paper birches with substantial white spruces beyond. These, in turn, overlook the creek bottom. Along the creek, the few trees are mostly dead, killed by winter ice. Out of sight behind me, up on the hill, the forest transitions from white spruce with a few birches to a stand of aspens at the top.
Amy and I keep a pretty close look on the birds and wildlife that visit our little corner of the boreal forest and we’ve built a pretty good bird list. New species, or changes in abundance tend to catch our notice.
Such a change has happened this fall with a major influx of woodpeckers. Just about every day a big male Hairy Woodpecker appears, squawking and pecking and then disappearing. Though I can’t be sure, I presume it’s the same individual each time. We’ve also had a pair of Downy Woodpeckers hanging around, and a rare Three-toed Woodpecker has been a regular visitor for the past week or two.
All these species we’ve seen before on the property, but never so consistently. Nothing big has changed in our behavior, we haven’t even been consistent with the bird feeders this year. No question, we’ve got more woodpeckers.
The forest around us though appears to be changing. We’re experiencing a die off of spruces. We have some great big white spruces scattered across the property. Last year, a big one fell up on the hill, it was already dead when it toppled and I promptly chopped it up into firewood. One of our favorite trees, a grandfather of a spruce that leans over our two-track driveway, started oozing sap near its base and this summer and I noticed it was being attacked by carpenter ants. It now looks sad, with brittle needles falling. I don’t think it has long to live.
There are more too. The few living trees remaining along the creek are showing signs of stress and though I don’t keep as close track of those, I’m sure there are more standing dead then there have been in years past.
And thus… woodpeckers. Dead wood is vital part of the boreal forest ecosystem. The stuff hosts the aforementioned carpenter ants and wood-boring beetles. And these are favorite foods of the woodpeckers. The species of dead tree also plays a part in what species of woodpeckers appear.
As I was looking into this a few days ago, I found a paper from the journal Forest Ecology and Management which looked into tree selection by woodpeckers in the eastern boreal forest of Canada. Though it’s not identical habitat to that around my home here in Fairbanks, it’s not too far off.
The researchers looked into three habitat types: mixed woodland, conifer forest, and burns. What they found is that woodpeckers are pretty darn selective about habitat and foraging tree.
Species like the Yellow-bellied Sapsucker (which are rare in Alaska’s interior, and I haven’t yet found one on my property) are strongly correlated with mixed woodland and nearly absent from conifer forest. While Three-toed and Black-backed Woodpeckers are closely tied to conifers (and the Black-backed to burns as well). Downy Woodpeckers were exclusively in mixed woodland while it’s close relative the Hairy Woodpecker was the only species to split its time between habitats (present in conifer forest about 1/4 as much time as in mixed woodlands).
Woodpeckers also preferred different stages of decay. Sapsuckers and Downies selected live, but decaying, deciduous trees. Hairy Woodpeckers seem open to foraging on all types of trees, live or dead, in all stages of decay, while the Three-toed and Black-backed both avoided deciduous trees and preferred recently dead conifers.
All of this fits pretty nicely into what I’ve seen here at my cabin this fall. The increase in recently dead or dying spruces seems to have lured in the generalist Hairy Woodpeckers and the niche specialist Three-toed. The pair of Downies are a bit more of a mystery with their preference for dead deciduous trees, but maybe we have something going on in the birches and aspens on the hill above the cabin.
Checking that out sounds like a good excuse to get away from my computer this afternoon.
The paper I refer to in this article:
Nappi, Antoine, Pierre Drapeau, and Alain Leduc. 2015. How important is dead wood for woodpeckers foraging in eastern North American boreal forests? Forest Ecology and Management 346:10-21.