It might seem obvious that if you wanted to ensure a bird’s survival, you would make sure its habitat was secure in both of its homelands, and that the tie between winter and summer habitat was well understood. But outside of a couple of species—Kirtland’s being one of them—“that idea is just not gaining ground,” says Smithsonian migratory bird researcher Dr. Peter Marra.

To change that, the Smithsonian has supported Marra and other researchers in conducting intricate tissue studies comparing Kirtland’s tissue from its wintering grounds to tissues from plants and insects in the wintering grounds to see if what the bird is eating affects how early it arrives Up North. The tissue study is a global first in ornithological endangered species research.

Among other things, Marra hopes to determine where the healthiest birds are spending their final weeks in the Bahamas prior to flying northward. The idea being that if you can identify the habitat that’s producing the healthiest birds, you can work to preserve or plant that habitat. “If we don’t protect the wintering grounds, it doesn’t matter how much you do in your own backyard,” Marra says.

Beginning in spring 2006, Marra and his team trapped the early arrivers—an indication that they are strongest—and plucked tiny feathers, drew blood and clipped toenails before releasing the birds. Back in the lab, researchers analyzed the samples for isotopes of carbon, hydrogen and nitrogen. What do they hope to learn? Take carbon as an example. As a plant produces tissue, the tissues have a specific carbon fingerprint that can be read through isotope analysis. The remarkable thing is that this fingerprint transfers to the tissues of insects and animals that eat the plant. So, say an insect eats a snowberry in the Bahamas, and then a Kirtland’s eats the insect. The snowberry’s carbon fingerprint ends up in the Kirtland’s tissues. Analyze the Kirtland’s toenail and you can determine the plants growing where he’s been living. At least that’s the theory. The work is delicate and the carbon fingerprints not always as distinct as one might hope.

Photo(s) by Lou George FWS