A Douglas fir grows in my yard. It's one I planted soon after moving to the property years ago. Now it's more than 30 feet tall and doing quite well.
One tree hardly makes a forest, but the three visitors to my yard weren't complaining. They were chestnut-backed chickadees, common birds of our Douglas fir forest. They have a sooty gray cap and chestnut-colored back and sides.
Once a decade or so, some individuals descend to the valley floor. This appears to result from a failure in some critical part of their food supply forcing them to disperse.
Wandering out of their normal habitat, these few encountered my Douglas fir. They were busily moving in and among the limbs, inspecting the cones hanging from the smaller branches, checking out the buds and occasionally giving their soft calls as they foraged. They didn't visit the incense cedar next to the Douglas fir or the madrone, ash or cottonwoods in my yard but remained in the fir.
If you don't have Douglas fir, you don't have chestnut-backed chickadees. It's that simple.
It is observations such as these that make a biologist wonder. Why do chestnut-backed chickadees forage almost exclusively in this one kind of tree? Are their legs and feet best equipped to perch in Douglas fir? Do they know how to find insects, spiders and cocoons best among the short needles of Douglas fir?
At higher elevations you will find mountain chickadees, a chickadee with a distinctive white line over its eyes. Like the chestnut-backed chickadee they have a preferred tree species in our area. They live among white fir. Around Howard Prairie, the Douglas fir forest meets the white fir forest. Chestnut-backed chickadees and mountain chickadees also meet here. I have watched a mixed flock of the two species move deliberately through the forest as they foraged. Chestnut-backed chickadees flew from Douglas fir to Douglas fir, skipping over the white fir. Mountain chickadees moved from white fir to white fir, bypassing the Douglas fir. This is not to say that they never feed in other trees, but they do have clear favorites.
There are two other "chickadees" in Jackson County. One is the oak titmouse, a plain gray bird with a short crest. I'll wager you can guess which tree species this member of the chickadee family prefers.
The final member of the group is the black-capped chickadee, a bird of riparian habitat. You can easily find them along Bear Creek. This species is not as particular as its close relatives and inhabits a variety of deciduous trees. It is a familiar visitor to backyard feeders and will even share oaks with the titmouse.
This kind of specialization is common among forest birds. Nuthatches, too, have their preferences for particular trees. White-breasted nuthatches prefer oaks. Pygmy nuthatches prefer Ponderosa pine, and red-breasted nuthatches prefer conifers other than pines, including both Douglas fir and white fir.
I wonder what would have happened if I had planted a white fir along with my Douglas fir years ago. Maybe then I would have had the occasional mountain chickadee in my yard. Before I hear from the botanists, I know the white fir never would have thrived near the valley floor, but still, it is fun to consider.
Stewart Janes is a biology professor at Southern Oregon University. He can be reached at firstname.lastname@example.org.