Tuesday, November 24, 2015
Rarity season continues: a week or so ago, some experienced birders spotted a small flycatcher in Central Park's Ramble, near the Boathouse cafe. The bird was a member of the genus Empidonax, which all have eyerings and wingbars, and are notoriously hard to identify as specific species with certainty. It had a yellow wash on the breast and belly, and they identified it as a Yellow-Bellied Flycatcher.
Some days later, other birders re-found the bird. They say that it had a very large eyering, and the eyering was kind of teardrop-shaped, and then the game was on. By Friday, the area was flooded with birders--because, you see, that kind of eyering is a hallmark of a "Western Flycatcher", and so the bird was thousands of miles out of its normal range, a screaming rarity that everyone list-making birder wanted to see, the second (or maybe first) record of this kind of bird in New York State.
Cool! Elena and I were planning to meet some friends for a walk in the Ramble on Saturday. Our friends aren't really birders, but they're interested, and we got to show them three excellent species. We easily found the continuing Great Horned Owl, and the Red-headed Woodpecker who is settled in for the winter. Then we joined the mob of bird paparazzi looking for the flycatcher.
We got a couple of nice, though brief, looks at it--little greenish-backed bird with messy plumage, distinctive eyering, feathers on the crown very spiky, basically rather rumpled from its wild journey across the country. And all the mobbing birders also got good looks at the scruffy little vagrant, and many photos were taken. Excellent.
There's just one problem. "Western Flycatcher" isn't a species. It's officially two species, Pacific-Slope Flycatcher and Cordilleran Flycatcher, and--remember I called the Empidonax flycatchers notoriously hard to identify? These two are almost completely impossible to separate, except by the region they nest in. Which in this case is no help. Until the late 1980s, they were considered one species, and a lot of people think that the split is poorly-founded. Even if you have a bird of each species in your hand, the are simply no physical characteristics to tell them apart.
This could not stand. Birders, list-making birders, especially rarity-chasing birders ("twitchers") want--no, need--a species ID.
So the crowd watched and watched, on into Sunday. More photos were taken. The bird wasn't vocalizing--the call is usually a good way to separate empid species. In this case the calls are almost identical, but if they got a recording, a sonogram might tell which kind we had. Eventually, it called, and they recorded it. And a careful observer saw the bird poop and collected the output; maybe they can analyze its DNA from that. I'll let you know if I hear any results.
I slept poorly Sunday night and was up early, so I went to the park before work. I ran into Corey Finger of the 10,000 Birds blog, and we watched the little bird for a while. It was fairly cooperative--I was finally able to get some photos (my view on Saturday was too brief).
For myself, I'm happy to just call it "Western Flycatcher". But who knows, it might turn back into a species, if the American Ornithological Union ever has second thoughts about the split.