A pair of house wrens (Troglodytes aedon) were particularly active near our field camp in the Black Hills National Forest, near Sundance, WY. House wrens are common in North American woodlands, and are known cavity nesters. Typically, a nest site will be chosen in a tree, though in urban areas, the birds are known to choose any “cavity” that will do, such as a drain pipe or a parked car.
My field crewmates and I were camped in an open woodland on an old closed logging road. Each day, midsummer thunderstorms rolled through and left us soaking wet. With few other options, we hung items like wet socks to dry on a barbed wire fence. After my bright red, Belizean draw-string bag had been hanging out overnight, I noticed an increase in house wren activity near the fence. After watching the male disappear more than once with pine needles in his beak, I walked over to check my hanging bag on a hunch.
The male had already built up a good handful of dead Ponderosa Pine needles in the bottom of the bag. I would later learn that the males are known to build several nests at once, before the female chooses her preferred nest and finishes it with a lining of feathers or other materials.
Unfortunately, I did not wait to find out if the female would choose my bag as the best nest site. I removed the materials and set them on a nearby fence post to see if the male would reuse the pine needles he had accumulated.
The wren flew to the spot where my bag had been, pine needle ready in his beak. He looked carefully for it, flitting around the spot a few times, before deciding he had not just misplaced it–the nest site was gone. I watched him revisit the nest pile on the fence a few times, and by that evening, the whole accumulation had been moved elsewhere.
I can only hope his other nest “cavities” were more suitable choices!