An Oddity at Old Basso Bridge: A Possible Melanistic Ash-throated Flycatcher

Sometimes one sees the strangest things out there. I was busy social distancing with Mrs. Geotripper up the Tuolumne River a few miles where a hundred-year-old bridge was replaced by a modern span back in the 1980s. Old Basso Bridge remains at its original location, but only pedestrians are allowed to cross it. The bridge is a good spot for birding, being a high observation deck for spotting avian creatures in the adjacent underbrush and trees. We are especially drawn there in the spring because Ospreys have adopted the bridge as a nesting locality and because it is a fairly dependable place to spy Phainopeplas.

I saw a dark shape in the Russian Olive thicket, and thought I had found a Phainopepla, but noticed  that it had no crest or red eye. The problem is that I didn't know what it was. The more I studied the pictures, the more I realized it looked in all but color like an Ash-throated Flycatcher (Myiarchus cinerascens). I searched the internet, and played with photoshop to see if I could turn it into a normal flycatcher, but had to give up. I made inquiries on the Flycatchers of North America and Birding California groups on Facebook, and most of the speculation coalesced around it being a melanistic Ash-throated Flycatcher.

Melanism is a genetic mutation that results in additional pigmentation in the feathers. It happens in a number of different birds and has been documented in several species of flycatchers. I couldn't find anything about melanistic Ash-throated Flycatchers, so unless there is some more documentation from those who know more about birds than me, I will leave this as a hypothesis. But an intriguing one.

I went out two days later to see if I could find the bird again and was unsuccessful, but I did find one or two normally pigmented Ash-throated Flycatchers, which I've added here for comparison's sake.

This has been a strange year for me and strange-colored flycatcher species. Last October I discovered a leucistic Black Phoebe at the Merced National Wildlife Refuge (leucism is a mutation causing a lack of sufficient pigmentation leading to light coloration). I've seen both ends of the gray spectrum!

Leucistic Black Phoebe at the Merced National Wildlife Refuge in the Central Valley of California, 10/18/19.