For two days I’d been pulling weeds down in the flatlands resulting in awful hay fever of the kind that prevents good sleep. You keep waking up gasping for air if at any moment your mouth slides shut because nothing, not even a single molecule of air, can get through your nose. But now I was 3500 feet higher, at a mountain cabin and the hay fever had subsided. It was early afternoon, the perfect time for a nap. Warm outside, the cabin was pleasantly cool and the couch beckoned. Tired as I was from lack of sleep, the prospect seemed delicious.
Somewhere down the hypnagogic slope to sleep, in that place just before unconsciousness where weird things happen, a great clattering began echoing around inside my head, bouncing from side to side so loudly I was certain my head was a hollow tree. The noise continued unabated as I resolutely tried to drive past it into real sleep. I deserved a nap, or so I thought.
But the pounding continued and so I began rising back up the hypnagogic slope and came to realize the racket wasn’t inside my hollow head at all, it was inside the hollow cabin, bouncing off the walls in a cataract of noise. One rap hadn’t finished its journey before another began. It felt like being inside one of Gene Krupa’s drums.
“Woodpecker,” I thought, by this time fully awake. “How did a woodpecker get inside the cabin?”
But not inside at all. Outside. But which way? From the echoing, I couldn’t tell. The din was unbelievable.
And here was the culprit.
Pounding away on 70-year-old cedar shakes on the west side of the cabin. (I assume the bugs weren’t that old.) The east end of the cabin is even older, 106 years and woodpeckers have been after it in the last few years as well. I figure as long as they don’t poke holes through the walls on top of the logs, that I should let them eat whatever they want.
At first, it wasn’t clear whether the nap-robber was a Downy or a Hairy Woodpecker. Both species look remarkably alike, from the red crown of the male all the way down to the white spots on the side.
But the Hairy Woodpecker is bigger, about nine inches long. The Downy is only about 6.5 inches long. I suppose that is the best way to tell them apart: Downies are smaller, more petite, and cuter. You can tell that this bird was larger than a Downy from this photo.
The cabin was built in the old days, back when a two inch by six inch piece of lumber was actually two inches by six inches, unlike today. You see that the bird was at least 8 inches long because he covers the six inch side of one board plus the two inch side of another.
Even though the two species of woodpeckers look almost identical except for size, they are not close relatives. Examples of “convergent” evolution, they evolved similar appearances from different lineages. The classic example of convergent evolution is the wings of birds and bats. Structurally similar, the bat wings are attached to mammals.
The wild world is full of other examples. The Pronghorn Antelope of North America is only distantly related to the true antelopes of the Old World, but looks and behaves similarly, probably because both occupy analogous positions in their respective ecosystems. None of the five species of freshwater dolphins are closely related.
Sometimes only one or two traits evolved convergently. Platypus have something that looks a lot like a bird’s beak. Possums have opposable thumbs. Peyote cacti of the desert and Ayahuasca vines of the Amazonian rain forest produce the same toxin, probably to deter predators. (Although that is not always successful if the predator is human.) The anti-freeze protein of deep-sea Arctic fish is the same as the protein in the unrelated deep-sea fish of the Antarctic.
In the world of birds, in addition to Hairy and Downy Woodpeckers, other examples include the wrens and robins of Australia which look like northern birds, but are not close relatives. Flightless penguins of the Southern Hemisphere evolved independently from flightless, wing-propelled, diving auks of the Northern Hemisphere. The Turkey Vulture riding the wind in our last post is not in the same family as Old World Vultures. (In fact, no one knows for sure where Turkey Vultures came from.) Both have featherless heads, are large, flock in trees, soar for hours, and circle carrion before landing, but only Turkey Vultures use smell as well as sight in the hunt for dead flesh.
But, as far as I can tell, the The Red-crowned Nap-Robber is new to science, so I don’t know if it too is an example of convergent evolution. Personally, I doubt it. I suspect it is a cousin of the better known Yellow-bellied Napsucker.