Some bird behavior can be expensive

Last month I wrote about somewhat perplexing behavior of acorn woodpeckers. They become a little overzealous in their harvest of the acorn crop and fill nest boxes with acorns, never to be seen again.

A reader from the Redding area informed me that my birds are amateurs in the area of goofy behavior. The reader just finished removing 37 gallons of acorns from his gutters. He estimates this represented 15,000 acorns. His tone was less than amused. His neighbor was even less amused with the plumbing bill he received. It turns out plumbing vents in the roof appear to be suitable places to store acorns in the eyes of acorn woodpeckers. Just how many acorns it takes to clog a 4-inch diameter drain pipe isn’t clear, but it is certainly more than the few thousand acorns I found tucked away in the bird boxes on my property.

If not for the protection from the Migratory Bird Treaty Act, the woodpeckers might have a serious problem. The reader suggests quarter-inch mesh galvanized screen over the tops of the plumbing vents. I think I might follow through on this suggestion.

It isn’t that the woodpeckers are dumb. It’s just that humans are something new in the evolutionary experience of birds. Natural selection should take care of the problem in a few thousand years as those prone to overworking and wasting resources are weeded from the population. In the meantime, expect to deal with acorn overload from time to time.

This isn’t the only example of odd bird behavior in response to human activities. Mirrors and windows with their reflections are also new to birds. I suspect many have experienced the annoyance of territorial males beating up on windows and encouraging houses to move along. Birds are slow to acknowledge that houses don’t intimidate very easily. Towhees are the worst, as they are ground scratchers. They have muddy feet and make a mess out of windows. One spring a male western bluebird took issue with my pick-up in the driveway. As hard as it tried, the side mirror returned to the same spot every day after work.

On the other hand, birds have been quick to take advantage of other human novelties in the environment. Bullock’s orioles construct intricate hanging nests. Long fibers are required to build a pouch secure enough to contain a rambunctious brood of growing young. I have seen some spectacular nests. One sparkling nest was made almost entirely out of tinsel. Other nests include an abundance of fibers gleaned from worn blue tarps. Then there are the nests constructed largely from fibers plucked from orange baling twine. One pair with a decorator’s eye used an equal mix of blue and orange fibers.

Then there are crows. Some have figured out an easy way to get a meal thanks to humans. Placing walnuts on a road for neighborhood SUVs to run over is a lot easier than hacking at them or dropping them from a height onto a hard surface over and over until they crack.

Before you think all woodpeckers are naive about all things human, flickers and others have found metal gutters to have excellent acoustic attributes in spring. Annoying perhaps, but this comes without a $3,500 price tag.

— Stewart Janes is a biology professor at Southern Oregon University. He can be reached at janes@sou.edu.

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