Biology Reference
In-Depth Information
ance meant fires or hurricanes. Today, however, it's human activities. “So we hypothesized
that disturbance by humans actually favors the spread of fruit plants used by the warbler.”
The test of their hypothesis led to one of the most surprising and counterintuitive discover-
ies in the history of ecology. “In the Bahamas,” Joe told me, “at least for Kirtland's warblers,
goats are kind of a blessing!” The ecologist's scourge of the earth, the common goat, was
resurrected as a hero. Here's why. The goats ignore the leaves and stems of plants that sup-
ply the Kirtland's with fruit and instead consume the competing plants. Thus they delay plant
succession, the process by which a natural community moves from a simple level of organ-
ization to a more complex assemblage. Succession is a natural process that typically occurs
after some form of disturbance has simplified the system. “In fact,” Joe continued, “our work
shows that goat farms make great Kirtland's habitat.” There are probably dozens of biologists
who work in Hawaii, the Galápagos Islands, New Zealand, and other islands where goats
were never part of the native mammalian fauna who would pay Joe handsomely to keep quiet.
Goats are often the worst culprits in the extinction of rare native plants, and they typically
outcompete native herbivores for forage. On Eleuthera, at least for Kirtland's warblers, they
were a force for good, especially on parcels where farmers rotated their goat herds among
fenced rangelands to prevent overbrowsing.
Many questions remain unanswered about the Bahamian winter getaway. For example, as
in Grayling, natural fire regimes in the Bahamas may provide the disturbance essential to
support the fruiting shrubs upon which Kirtland's warblers depend. But are today's managed
fire regimes too different from wildfires of the evolutionary history of the Bahamas? Are goat
farms and smart, “green” bulldozing practices enough to offset the suppression of fire? Fin-
ally, little is known about the habitat needs of the warblers during their critical three-week
migration from Eleuthera to Grayling.
As we walked through the pine grove in Grayling, Sarah reflected on my first impressions
of jack pine landscapes. “I had the same response as you did when I first arrived!” she ex-
claimed with a laugh. “It may not be very spectacular at first glance, but the more time you
spend in the jack pine forest, the more you appreciate that it has its own beauty. You can
be on a little hill in the early morning, watching the mist that settles in the low places when
the sun rises. I often see spruce grouse, upland sandpipers, porcupines, fawns, occasionally a
coyote. There really is a lot to like about it!” Sarah was starting to think like her study bird.
Her biggest challenge had been learning to nest-search. The difficulty of finding nests of
a study species, or the inability to do so, has probably derailed more potential PhD disserta-
tions in ornithology than any other obstacle. Sarah stopped to look under a pine. “The nests
