Damn I love the rivers that run through the Mud Keys. They are just the perfect distillation of the raw beauty of the backcountry, a world simplified down to the elements of water, mangroves and sky. We puttered through them slowly, as the law and any sense of aesthetic appreciation of the universe required, and the world was as peaceful as it gets. The only sounds were the burbling of the outboard, the lap of water against the hull and the occasional slow-speed flyover of one of the Navy jets coming in to land at Boca Chica, though it was amazing how quickly the noise of the jets faded.
There were some storm clouds out there, but nothing too close or too ominous.
I think the only thing better than getting out there and exploring a place like that is getting to show other people how gorgeous it is. And I was with a trio of the resident artists staying and working at The Studios of Key West this month, one of whom was doing a project on mangrove forests, and after she told me, all I could think was “Egads, this woman needs to see the Mud Keys.”
We’d found a pretty nice, out-of-the-way spot, and I was trying to figure out where to throw an anchor when I heard the song.
I don’t have a deep catalog of birds I can identify by call, largely because we don’t have a wide variety of birds that sing in the Keys, but I recognized this one.
It wasn’t the strident referee whistle of the gray kingbird, or the endless, improvised scat of the northern mockingbird. It wasn’t the guttural, staccato syllables of the mangrove cuckoo, or the rising scales of the prairie warbler.
The song was clear and clean and melodic, but also almost punk in its speed and pace.
I remember seeing an interview with one of the Ramones who said the real goal when he was playing a song he’d played for 20 years was to do it faster every time. And it was like that, only melodic, and with less fuzzbox and feedback, and maybe played on some kind of wind instrument lost to history.
The call was that of a new species, the mangrove yellow warbler.
Calling it a new species is probably a little confusing. Mangrove yellow warblers have been singing in the mangrove islands of the Keys as long as there have been mangroves in the Keys. But until last fall they were considered simply the yellow warbler, a species that bred from Ecuador, across the Caribbean, all the way up to Alaska and the Northern Territories.
Some of the yellow warbler population was migratory, some was not.
Following genetic testing of different populations of the yellow warbler, ornithologists decided they were two separate species – the northern yellow warbler, which is migratory, and the mangrove yellow warbler, which is not.
This simplifies things in some ways and complicates them in others. The newly dubbed mangrove yellow warbler has two subspecies, a primarily mainland-based one called the “mangrove” mangrove yellow warbler, and a primarily Caribbean one called the “golden” mangrove yellow warbler.
The males of the mangrove subspecies are somewhat easy to identify, as they have a rusty red head that contrasts dramatically with the smiley-face yellow that makes up the majority of the plumage that covers their body. The adult males of the golden subspecies – the ones we have here – have the same smiley-face yellow body, but instead of a rusty head, a more discreet and subtle rusty red cap.
Distinguishing the golden subspecies from the northern yellow warbler is nearly impossible for the unpracticed eye. The famed bird artist and identification guru David Sibley has been working out how to do so on his website, but so far it is a slough of subtle distinctions. Structurally, the bill on the “golden” mangrove yellow warbler is ever so slightly more down curved, and the undertail covert feathers slightly shorter. The northern yellow warbler has a slightly sleeker body and slightly longer wings, which aid them in flying the long distances required to migrate.
Plumage-wise, there are slight variations between the first-year birds, the adult females and the adult males. But it’s complicated.
Sibley made some helpful illustrations with a lot of side-by-side comparisons on his site. And if I had two birds from the different populations standing next to each other and perfectly still, as they were in the illustrations, I might be able to sort out the difference. I’m a relatively solid birder, but in the field this distinction is beyond my level of competence.
Still, there are ways to figure things out beyond field marks.
The bird I was hearing was lurking in the mangroves. I managed to get a few shots of it after I anchored the boat, but I only had the quickest glimpses. No time to get thoughtful or analytical. And the angles were not great to make out the subtle distinctions of the field marks.
But I knew I was right. It was a mangrove yellow warbler.
Northern yellow warblers migrate through the Keys twice a year, and you occasionally see one in the winter.
Mangrove yellow warblers are here year-round. The Keys and the Everglades are the northern part of their range. There are a few places you can see them in the mainline Keys, but they are far more numerous and easy to find in the backcountry.
The reason I could be confident in my ID was, while there may be some stragglers, the migration is pretty much over for the season. Which was a good indicator. But also, the bird was singing. And birds don’t sing for the beauty of the song. They sing to attract a mate and define their territory. Which means this bird bred out there in the Mud Keys. This was his home.
