And before poor Dave gets into his head that I’m going to stop joshing him, I have to share the story of the ceiling fan birdnest. The area around the ranch is habitat for the black-tailed gnatcatcher (Polioptila melanura), and they spend most afternoons and evenings snagging as many insects as they can manage. When not hunting, they spend their time watching us crazy humans, mostly to take advantage of the situation.
“Taking advantage of the situation,” in this case, refers to using appropriate human structures to facilitate their own nestmaking. Specifically, they like using the house located on the property, particularly the big open deck on the back. Shortly after arriving at the ranch for the last big family gathering, my sister-in-law found this nest atop a ceiling fan over the deck, and a quick peek showed that it had eggs and at least one hatchling.
Getting up to the nest to observe further had issues, the least of which was the lack of head clearance above the ceiling fan blades. Tilting the blades to get a better view risked knocking the nest off the fan. In the end, my nephew Bruce and I settled for putting cameras up to the nest, taking whatever pictures we could, and backing off before the parents came back. After doing so, we had a bit of a surprise.
If you’re observant, you’ll note that the hatchling inside the nest, while still blind and helpless, is considerably larger than its eggs. You may also note that the eggs aren’t the same color. That’s because both the hatchling and one of the eggs both belong to a brown-headed cowbird (Molothrus ater), which is also common to the area. Cowbirds get their name because of their otherwise encouraging habit of picking ticks and other pests from cattle, bison, and other big herd animals. Since bison herds are migratory, the cowbirds evolved to take advantage of other birds’ instincts and parasitize them. The mother cowbird arrives at a nest while the parents are gone, lays one to two eggs, and moves on, reasonably assured that the foster parents will lay on the clutch and feed the hatchlings as they emerge. Gnatcatchers seem to be particularly susceptible, with reports of 100 percent parasitism of all gnatcatcher nests in surveyed areas.
This led to quite the spirited debate. My sister-in-law argued for scaring off the gnatcatchers so the cowbird chicks would starve, being offended by the idea that the cowbirds were parasites. I argued instead for leaving well enough alone, because at least this way the gnatcatcher eggs wouldn’t be a complete waste. Besides, being very much unlike my own family, I could appreciate the cowbird chick’s situation. We left that weekend with the nest intact, and I suspect that I might see one of the cowbirds the next time I visit, inexplicably relieved that we left it alone. And so it goes.
