Biology Reference
In-Depth Information
Male Kirtland's warbler (
Dendroica kirtlandii
) on a jack pine branch
The bold male in the snag spent the next fifteen minutes throwing back his head, bobbing
his tail, and filling the air of the jack pine grove with his lively song. Such lovely plumage
in the bright sunshine brought cheer to everyone. Nearby, Nashville warblers began singing.
Kirtland's and Nashville warblers, along with the other fifty-four species of New World
warblers that breed in the United States and Canada, are part of nature's balancing mech-
anism, as these dedicated caterpillar eaters, when gathered in numbers, clean the forests of
larval insects harmful to trees. They are also among the most stunning of pest removers. Nat-
ural selection, using delicate brushstrokes and a colorful palette of yellow, green, chestnut,
orange, red, blue, and black, has fashioned an exquisite array of tiny creatures—only one
warbler species is larger than a sparrow.
Unlike most other members of the warbler family, the Kirtland's was discovered relatively
late in the history of North American ornithology. It was first described by taxonomists in
1851, when a male was collected on the outskirts of Cleveland, Ohio. The songbird was
named in honor of Jared P. Kirtland, an Ohio physician, teacher, horticulturist, and naturalist
who assembled the first lists of vertebrates for the Buckeye State. Ironically, by the time the
Kirtland's warbler was named, it was already experiencing a range collapse, and by the time
of Kirtland's death, in 1877, it may have disappeared entirely from Ohio.
The bird's wintering sites first became known in 1879, when a specimen was collected on
Andros Island in the Bahamas. Since then, wintering Kirtland's warblers have been found on
other islands in the Bahamian archipelago, on the Turks and Caicos Islands, and on Hispani-
ola. Yet only in 1902 did biologist Norman Wood find the first nest, in Michigan's Oscoda
County. Like many of the more than 200 species of migratory songbirds that nest in the Un-
ited States and Canada, the Kirtland's warbler actually spends eight months of the year on its
wintering grounds.
Among the birders in our makeshift Grayling caravan was Sarah Rockwell, a University
of Maryland doctoral student who in 2006 had chosen this bird to be the center of her life for
the next five years. When I first heard of Sarah and her work through a colleague, I wondered
why in the world she would undertake such a study. Successful PhD dissertations in biology
are all about large sample sizes. Piles of data are essential for the rigorous statistical analyses
and testing of hypotheses that graduate committees demand from students. Indeed, professors
typically divert their more idealistic or naive students from the futility of field studies on rare
species.
A major reason she became interested in studying Kirtland's warblers, Sarah explained, is
that she really liked the idea of contributing to conservation efforts in her home state. When
working with an endangered species, any data one can gather on its ecology might be imme-
diately useful to managers. “Besides,” she noted, “I actually have no problem with sample
