A small face stared out from inside the nest box. It looked a little odd. When I approached closer, it wasn’t a face at all. It was an acorn. This was more than a little odd. The box held more than 200 acorns.
It was a banner year for acorns, and the scrub and Steller’s jays in my yard have been doing their best to collect and bury them all. But who filled the box on my garage? Not the jays. They store acorns one at a time scattered over a wide area. There are gray squirrels about, but there was no way they could get to the box tucked neatly under the eaves.
It could only be acorn woodpeckers. They, too, have been busy taking advantage of the bounty provisioning their granary for the year.
A granary is a tree or a couple of trees in which they have drilled hundreds if not thousands of acorn-sized holes. They tap acorns firmly into each for later use. Not only does the granary sustain them through the winter, it is a valuable resource when raising young and on until the next harvest.
Once the granary is filled, there is little time to drill additional holes. Granaries can contain up to 10,000 holes and take years to create. They are a critical resource for the acorn woodpecker, and a granary is nearly always monitored and protected from thieving squirrels and jays by at least one member of a colony. Colonies may consist of up to about 10 individuals. The loss of a granary tree often means the end for a colony of acorn woodpeckers.
Once the granary is fully provisioned, it would seem time to kick back and enjoy the fall colors, but not for acorn woodpeckers. Being a species with a type A personality, they go a little crazy and move on to plan B. Now here is where I question the intelligence of these woodpeckers. They fill or attempt to fill every opening they can find. On my property that means nest boxes.
Last weekend I began to clean out the nest boxes used by the swallows, chickadees, titmice and house wrens on the property. As I opened box after box, most contained acorns. Some held 20 or so. Other boxes were filled up to the entrance and contained hundreds. In one box, acorns neatly filled a house wren nest like so many eggs. I ended up emptying well over 1,000 acorns from the nest boxes on the property.
This was a monumental waste of time and energy for the woodpeckers. The entrances to these boxes were designed for birds much smaller than an acorn woodpecker. From the moment they dropped an acorn into a box it was gone, never to be retrieved. It was like dropping a letter into a mailbox on a city street. Considering the effort to fill all the nest boxes, I would think they would choose more wisely. Apparently not.
Now you understand my thoughts about the intelligence of these birds. Still, they are immensely entertaining, and they won’t be going hungry anytime soon. If you wish to check out a granary, there is a large one at the end of the parking lot in TouVelle State Park.
— Stewart Janes is a biology professor at Southern Oregon University. He can be reached at firstname.lastname@example.org.