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Bird-watching
in the Abacos By Alice Bain Recently Abaco paid host to two field workers from Glasgow University who are studying the rare Kirtland's Warbler. Dr. Stuart Bearhop and Mr. Steve Votier, guided by local Dolphin Researcher Colin McLeod, spent four days at Hole-in-the-Wall armed with mist nets, sun block and bug repellent and returned to civilization on the third of May, hopefully with enough data to shed some light on the wintering habits of this reclusive bird. The Kirtland's Warbler is a small migratory bird, and there are estimated to be only 2,000 of them left in the wild. They spend their summers in a small area of the Michigan and breed in the Jackpine forests there. Where the warblers spend their winter is somewhat of a mystery, there are so few of them that it is extremely difficult to track them down. It is known, however, that they all winter somewhere in the Bahama archipelago (including the Turks and Caicos islands to the south). At first it may seem puzzling that Bearhop and Votier chose early May to do their research here"after all, since this is the wintering ground, coming here in the summer should ensure a complete lack of Kirtland's Warblers. But the ways of modern science are subtle"bear with me as I explain. Most people exposed to the American culture are at least passingly familiar with the concept of a drug test taken from a hair sample. Any substance that a person ingests is processed by his or her body and eventually ends up in the hair shaft as a sort of "fossil record." The substances being looked for are usually things like cocaine, opiates, methamphetamines and other illegal drugs, but it is possible to tell much more from the hair sample such as a person's preferred diet"and indeed some specialists in the United States are using hair analysis to prescribe courses of supplementary vitamins based on lacks detected in the hair shaft. Theoretically, a specialist given some of your hair could tell if you were a vegetarian, or if you eat a lot of chocolate or pickles, or if you have a pack-a-day smoking habit. This is true of animals as well as humans"you can tell what an animal has been eating from isotope signatures in its hair, or in the case of Kirtland's Warblers, feathers. What an animal eats depends on where it lives, and it follows that a bird living in the mangrove swamps will have a different signature combination of chemicals in its feathers than one living in the pine forest. What our two wily scientists have been doing here is trapping what they call proxy species"birds that are resident here all year round and that have the same feeding habits as the Kirtland's Warbler that is, that eat mostly insects. Proxy species for Abaco are the Bahama mockingbird, the thick-billed vireo, the yellow warbler and the Bahama yellowthroat among others. When one of these birds is netted, a sample clipping of toenail and feather are taken and labeled (only body feathers are clipped, leaving the bird unharmed and with the unhindered ability to fly and continue about its business). Under analysis it is hoped that an overall isotope signature for the kind of habitat that the bird was trapped in (pine forest, coppice, mangrove swamp) can be established and compared with data obtained from feather and toenail clippings taken from Kirtland's Warblers trapped in their habitat in Michigan. This should tell the researchers what kind of habitat the warblers winter in. The concern here is the suspicion that Kirtland's Warblers may rely solely upon Caribbean pine forest (such as we have in Abaco) for their wintering grounds. This makes them extremely vulnerable to any changes in that forest such as logging activity or forest fires. If the Kirtland's are indeed reliant on pine forest for their wintering grounds and if those grounds have traditionally been in Abaco, the recent spate of fires here may be pushing these already incredibly rare birds further towards extinction. Warblers are being trapped for sample clipping in Michigan this May and June, and the results of the analysis will be known sometime during the first half of 2001. Abaco hopes for a bright future for these sprightly little birds, and Mr. Votier has been assured that his poisonwood rash will clear up in a few weeks. |
