Biology Reference
In-Depth Information
The hour was late, so we had to end the stakeout. Jack suggested that everyone come back
to Hakalau Forest during the breeding season (December through May), when the native
birds would be more active and vocal. Then the trees would be “dripping with 'i'iwis,” and
maybe an 'aki or two. Liba chimed in: “People expect all honeycreepers to be rare every-
where, given all the threats they face. But the dawn chorus at places like Hakalau Forest is un-
believable; it's deafening. I think songbirds are at higher densities here than almost any forest
I've visited.” Honeycreepers have declined in the lowlands of all of Hawaii's archipelago
partly because the dense forests of native plants have been replaced by a generic pantropical
vegetation including eucalypts from Australia, banyan trees from India, and jacarandas from
Brazil. On Oahu, if you relied on the most common plants to distinguish where you were in
the world, you might think you were in Bermuda, or St. Croix, or even a Club Med in the
Seychelles. Most of the trees and shrubs that line the roadside display large, showy flowers
in an orgy of colors, imported beauty that has increased the diversity of plants in Hawaii but
fails to attract its native birds.
Introduced species of birds and mammals are also responsible for pushing some of the
rare natives out of the lowlands. According to Thane Pratt, the leading authority on Hawaiian
birds, more than 170 alien bird species have been introduced onto the Hawaiian Islands, about
54 of which have established breeding populations. Like their floral counterparts, they came
from the world over—red-billed leiothrixes, rose-ringed parakeets, and bulbuls from Asia;
waxbills and canaries from Africa; cardinals and meadowlarks from the Americas. These and
most of the other introduced avifauna are all beautiful birds, but they don't belong in Hawaii.
The most pervasive factor accounting for the absence of native birds below 1,500 meters'
elevation is unexpectedly small. The accidental introduction of mosquitoes in the early 1800s
allowed avian pox and avian malaria to spread from infected migratory birds or species in-
troduced from Asia to the defenseless native birds, wiping out a number of species and pop-
ulations in the lowlands. The remaining species were those that ranged into the higher eleva-
tions, where it is too cool for the
Culex
mosquitoes to survive.
To imagine the 'aki and the other honeycreepers joining the dodo, the great auk, and the
elephant bird in the aviary of oblivion is a painful thought. Jack is concerned that with rising
temperatures resulting from global climate change, the temperature-sensitive malarial para-
sites could develop fully within their mosquito hosts. Then the disease could make its way up
the mountainsides and adapt to life in these forests, wiping out the remaining native birds as it
goes. (Studies of human malaria show its projected spread to higher elevations and latitudes
for the same reason.) Birds at still higher elevations might be safe for a while, but how much
farther uphill can they move before the forest gives way to the cinder fields characteristic of
the volcanic peaks?
The observatory by the summit of nearby Mauna Loa gives us some context for con-
templating that question. The Mauna Loa atmospheric carbon dioxide (CO
2
) measurements,
