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Once
Hawaii was for the birds. Before the arrival of humans,
it was birds, not mammals, which dominated the environment.
Today Hawaii's native forest birds are disappearing.
Nearly half of the 140 bird species that were known from
historic times are extinct and over 50 additional extinctions
have been identified from fossil evidence. Of the species
we have left, 31 are on the U.S. Endangered Species List.
Some of the world's rarest species of birds are Hawaiian.
Maui's endangered Po'ouli, one of the Hawaiian honeycreepers,
has an estimated population of 5 or 6 birds. Here on Hawaii
Island, the embattled Alala or Hawaiian Crow has a wild
population of around a dozen individuals. Though not as
rare as these, the dazzling scarlet honeycreeper Iiwi,
perhaps best represents the beauty, evolutionary wonder,
and endangered status of Hawaii's birds.
The
Iiwi is visually stunning. The adult birds have a brilliant
red body and black wings with a white patch. With the
reddest of red and blackest of black, they stand out brilliantly
in the infinite shades of rainforest green. Their colorful
plumage was used in Hawaiian featherwork, including Kamehameha's
famous cloak. Even when in the rare, thick, native forest
where the Iiwi flits about in high densities, I never
tire of watching this handsome creature.
Its
vocal repertoire is world-class. Once in Iiwi habitat,
you will hear the bird before you see it. Emanating from
the nearly six inch tall feathered songster is a surprising
diversity of rusty squeaks, sharp whistles, and gurgly
songs that end with a two note horn-like "beep-beep."
Along with its own original score, the Iiwi is a fine
mimic of the other forest singers. The Iiwi is gregarious
and the dominant noisemaker. Their continuous daylong
vocalizations combined with the other birdsong make the
forest sound like a symphony orchestra beginning to tune
up.
Despite
its beautiful color, the bird's most striking feature
is its beak. Long, curved, and salmon-colored, the Iiwi's
bill is a nectar gathering, insect probing, evolutionary
masterpiece. The Iiwi and the rest of its bird cousins,
the Drepanidinae or honeycreepers, evolved from a single
finch-like ancestor long ago. From this genetic colonizer,
sixty to seventy species arose. Many of them acquired
very specialized feeding niches. This speciation, known
as adaptive radiation, is most evident in the bill design.
There are thick, pliers-like, stout bills for seed eating.
The insect eaters have skinny, probing, long and short
bills. Some developed cross-bills for prying bugs off
and out of leaves. Others evolved strong prying and pecking
beaks to excavate insects out of shallow bark and bore
holes. The nectar gatherers, like the Iiwi, have bills
that are curved to fit in the deep recesses of flowers,
some fit perfectly into the native Hawaiian blossoms.
This type of evolutionary bird specialization, though
not unique to Hawaii, is unsurpassed. The Hawaiian honeycreepers
are arguably the world's best example of adaptive radiation
in the bird kingdom.
Not
only are the honeycreepers one of nature's great evolutionary
treasures, they are also one of world's most endangered
family of birds. Unfortunately, the same geographic and
genetic conditions that set the stage for Hawaii's remarkable
evolution also left them with poor defensive and competitive
survival skills. Once humans discovered and colonized
the islands, a process of deforestation and alien species
introductions dramatically transformed the islands' ecosystems.
By some estimates the islands have lost 70 to 90 percent
of its native forests. Along with this loss of habitat,
the presence of foreign plants and animals negatively
impact the Hawaiian species. Predators, such as cats,
rats, and mongoose that were intentionally or accidentally
introduced, find the Hawaiian birds easy prey. Exotic
birds, once established, are serious competitors for food
resource and breeding territory with the native residents.
Native Hawaiian species are being assaulted from many
directions. Scientists believe that the current population
crashes recorded are the result of a complex triangle
of pigs, mosquitoes, and epizootic organisms-bird disease.
When
I moved to Hawaii nearly eight years ago, Iiwi were readily
found at the Thurston lava tube in Hawaii Volcanoes National
Park. Today they are not found anywhere around the Crater
Rim drive except on rare occasions. On Molokai, the National
Biological Service's forest bird survey in 1995 recorded
only one Iiwi on the entire island. There are believed
to be less than a dozen surviving on O'ahu. The Iiwi
are dying from disease spread by mosquitoes. Pigs rooting
in the forest and eating out the starchy cores of tree
ferns create stagnant pools of water. These pools serve
as breeding habitat for introduced mosquitoes. These mosquitoes
bite exotic birds, some of which have bird disease in
their blood. The mosquitoes then bite the native birds
that have little or no defenses against these foreign
microbes. Once infected the Iiwi has shown a mortality
rate of 100 percent in some studies. Carter Atkinson,
a researcher from Volcano, has shown a direct correlation
between the amount of pigs in the forest and the level
of disease in the bird population--more pigs, more mosquitoes,
more disease.
It
is startling to look back through the historic record
and its collection of recent extinctions. It is disheartening
to listen to biologists lament this decline, or to read
the studies and research that document the numbers. But
it is deeply affecting to witness the decline through
your own binoculars. In my short time in Hawaii, I have
seen the loss. Biologist Jack Jeffrey of Hakalau National
Wildlife Refuge, calls the Iiwi "the essence of
honeycreeperness." With its splendid beauty and vivid
evolutionary adaptations it certainly lives up to that
moniker. I only hope it doesn't join that long and growing
list of extinct honeycreepers. The birds need intact,
native forest habitat to survive. Strategies to deal with
the exotic species along with forest protection and restoration
hold hope for our forest marvels. Perhaps with serious
financial and resource commitment, Hawaii will remain
a place for the birds.
Click
Here to see a selection of bird photos and
hear bird calls and song.
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