Biology Reference
In-Depth Information
more about Hawaiian ecology in advance, I would have saved some gasoline. Many native
Hawaiian birds and plants that are not yet extinct are fugitives, finding refuge on islands such
as Oahu only in mountain strongholds. On the Big Island, the birds are more accessible.
We continued in search of the palila, another honeycreeper species that resembles in its be-
havior and profile the pine grosbeak of North America. Having emerged from the rain forest,
we were now about 66 kilometers from Hilo, in the Big Island's dry forest zone, or what is
left of it. Cattle ranches lined the road; such pastures are widespread in tropical dry forest
areas globally. The climate and soils are more conducive to raising livestock than are the
pastures carved out of true rain forest and abandoned a few years later. The spread of cattle
on the Big Island has turned a continuous belt of dry forest composed of native
māmane
, a
leguminous tree, and naio, a kind of sandalwood tree, into a savanna with an understory of
introduced grasses. Today only about 1,200 palilas remain in the wild, and the species has be-
come the subject of a US Fish and Wildlife Service recovery program. We spent the next four
hours walking along the road on the slopes of Mauna Kea where, according to our birding
guide, the palila was supposed to be, searching māmane branches for a sturdy yellow-headed
honeycreeper. No luck.
The endangered palila population is an example of what can happen when a rare species
becomes too dependent on a particular food plant. The māmane is manna for the palila, and
when the trees disappear—as a result of pigs browsing the seedlings or the woodlands be-
ing cleared for cattle ranches—the birds vanish. The fate of the māmane is a prime example
of the potential ecological repercussions of introducing large plant-eating mammals, such as
cattle or pigs, onto an island where they never occurred naturally. The local species of plants
were unprepared for the invasion and had not evolved chemical defenses to deter herbivory.
There are also larger evolutionary processes at work here: the birds are so specialized on mā-
mane in part because the Hawaiian flora has become impoverished and in part because the
palila does not venture beyond a narrow range at midelevation on the Big Island.
Fortunately, on our way back to Hilo we took a wrong turn. Quite by accident, we found
ourselves facing a feeding party of palilas and an
'elepaio
, the endemic Hawaiian descend-
ant of an Australasian flycatcher. As we enjoyed the spectacle we had hoped to see, we also
scanned the panorama of hills and fragmented forest perched above the converted, sugarcane-
and pineapple-planted lowlands. The palila's strategy for survival became obvious, mirroring
what all resistance fighters know instinctively: when the invader advances, head for the high
ground—in this case, where the māmane forest was still present.
To improve our chances of seeing native Hawaiian fauna and flora, we continued a
search of Hawaii's uplands, choosing Hakalau Forest National Wildlife Refuge. Our group
was fortunate to have as a guide Jack Jeffrey of the US Fish and Wildlife Service, who
has been the force behind conservation at Hakalau for several decades. A young scientist
studying the birds of Hakalau Forest, Liba Pejchar, now an assistant professor at Colorado
