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It’s not easy being Green, less so Black-throated

May 29, 2008

It’s been a while since I’ve done my time at the North Carolina museum, even longer since I’ve written about it. This month has been busy. Between birding, my busted foot, and finishing the field trip season at the ol’ star factory* I haven’t been able to spent much time amongst the dead birds the last few weeks. But here’s an update and some background on the project I’m working on these days.

As you would probably expect, the work done at the NC museum primarily concerns birds within our borders and the greater Southeast. While the collection has some excellent specimens from all over the world, the vast majority are birds that were collected in North Carolina, and the research done by the ornithologists on staff concern birds that are primarily associated with the area. For instance, the museum does a lot of work with Swainson’s Warblers in both Carolinas, and with Black-capped Petrels, in partner with folks in the Dominican Republic where they nest, as both are fairly well-known to be birds of the southeast. But there’s another bird with an endemic subspecies population that is also unique, and far less well-known to birders in the United States.

The Black-throated Green Warbler is about as ubiquitous a North American warbler as there can be. Their zee zee zo zee rings out in nearly every forest east of the Great Plains as they head to their boreal breeding grounds. What you may not be aware of though, is that these regular BT Greens are nearly all of the nominate subspecies Dendroica virens virens. There’s a second subspecies, one whose population is far fewer, whose range is far more narrow, and who is endemic entirely to a thin band of swampy coastal plain running from South Carolina north to Virginia. This is the Wayne’s Black-throated Green Warbler, D. v. waynei.

First described by southern naturalist Arthur T. Wayne, these birds are morphologically distinct from the nominate BT Greens most everyone is familiar with. They tend to show smaller, thinner bills and a far less extensive black throat, which does not extend along the flanks as it does in the virens birds. I’ve lined up some typical birds in the photo below. The left two birds are waynei, the right two virens. Note the slighter bill and the whiter flanks on the Wayne’s birds.

In addition to the two distinctions mentioned above, Wayne’s birds tend to lack the dorsal streaking on the back you might see in virens. Check out the birds below to see. Again the left two are waynei, the right nominate virens.

The work that the museum is doing with the species involves taking detailed measurements of all the BT Greens, of both subspecies, in our collections as well as the borrowed specimens from collections all up and down the east coast. We’ve borrowed birds from the Smithsonian and the Harvard Museum of Comparative Zoology for instance, as well as those from smaller facilities, to get the largest possible sample of birds (some even from the collection of Arthur Wayne himself!). We’re trying to clarify the difference between the subspecies, not so much to make the case for a split, but maybe to justify spending a few more dollars for conservation of a distinct population that has recently been declining.

Anyway, there’s more BT Greens out there then you may have thought.

*not really a star factory, more like a planetarium

One Comment
  1. Jochen permalink
    June 2, 2008 3:23 am

    Come on, go for the split, I dare you!

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