In the middle of the afternoon a few weeks ago I was sitting in the public library in Sierra Vista, Arizona–a wonderful facility, by the way–escaping the heat of the day to download my bird sound recordings, recharge my batteries, and check my email, when my attention was drawn to a bird hopping directly toward me on the ground. No, it wasn’t in the library–it was on the other side of the floor-to-ceiling plate-glass windows, out in the desert garden. But it might as well have been in the library, because it ended up hopping right up to the window, less than four feet from my face, so that even without binoculars I could clearly see its pale yellow eye, its short, almost straight bill, its nearly-unmarked breast with a few spots front and center…in short, every field mark necessary to confirm its identity as a Bendire’s Thrasher–a scarce species I had seen only three times before.
And then, through the window, I heard it begin to call: a slightly noisy, one-syllabled note reminiscent of the “cheep” call of the American Robin. Naturally, I raced right out to record it:
The call note clinched the ID. It was completely different from the characteristic call of the very similar-looking Curve-billed Thrasher, the loud wit-weet! that is a trademark sound of the southwestern deserts:
I was particularly excited to record the Bendire’s because their one-syllabled call note had been described in the literature, but as far as I could tell, never recorded — I didn’t know of any commercially available recordings that included it, nor had I ever seen published spectrograms of it. The Macaulay Library didn’t have it, and in the two different mornings I’d spent recording Bendire’s Thrasher in Arizona and California, I’d never even heard it, much less caught it on tape. So I was pretty stoked.
I relayed the details of my sighting to my friend Andrew Spencer, who was due to arrive in southeast Arizona shortly after I returned to Colorado. He was equally excited about this rare recording opportunity, and he made a point of stopping at the Sierra Vista Public Library as well. That morning I got a message from him that relayed some good news and some bad news. The good news: he’d found the bird right where I said it would be, acting just as I’d said it would, giving calls just like the ones I’d recorded. The bad news? It had been accompanied by, and fed by, two adult Curve-billed Thrashers. It wasn’t a Bendire’s at all–it was just a juvenile Curve-billed.
Sure enough, when I went to look at the Bendire’s Thrasher chapter in Kenn Kaufmann’s Advanced Birding, there was the description of a juvenile Curve-billed Thrasher, matching my bird to a T. I had forgotten that Bendire’s has a pale base to the lower mandible, which my bird had lacked. And Kaufmann even mentions the single-syllabled call note of the juvenile Curve-billed. Blast.
The morals of this story:
- Juvenile Curve-billed Thrashers look and sound far more like Bendire’s than I ever thought possible;
- Even the most seemingly slam-dunk IDs can be wrong;
- I still don’t know of a recording of the call of Bendire’s Thrasher. Anyone? Anyone?