hawaii

GEOLOGICAL HOTSPOT

The Hawaiian Islands and their incredible biological diversity will forever be a source of wonder to people. They have fascinated me ever since 1998 when I was fortunate to have the opportunity to work with endangered birds on Hawaii for the Biological Resources Division of the USGS for a few months. In Feb-Mar 2006 I finally had the chance to revisit and take a few photographs.

Their existence is owed to a chain of massive shield volcanoes, the islands are but the tips of volcanoes. They are there because of a crack in the earth's mantle that has been spewing out molten rock for millions of years. The Big Island (Hawaii) is straddled across the hot spot and has active, dormant and extinct volcanoes. All of the other, older islands have shifted away from the hot spot. The Big Island is estimated to be about 1 million years old while Kaua'i could be 6 million years old.

The highest mountain peaks in the Pacific are all on the Hawaiian Islands. Mauna Kea (Hawaii)- 4205 metres (13,796 feet), Mauna Loa (Hawaii)- 4169 metres (13,677 feet), Haleakala (Maui)- 3055 metres (10,023 feet) and Hualalai (Hawaii)- 2522 metres (8,271 feet). Interestingly, Mauna Kea is technically the world's highest mountain when measured from the ocean floor being 33,476 feet!

Waimea Canyon, Kaua'i

BIOLOGICAL HOTSPOT

They are about 2500 km from the nearest continent (North America), making them perhaps the most geographically isolated land areas on earth. (In case Australians are wondering, it is about a 9.5 hour flight over the Pacific Ocean to Honolulu from Sydney).

All living things on the islands reached by wing, wind, waves or Polynesian boats. As occasional stragglers survived on the islands over the years, evolution transformed them into the enormous diversity of forms that eventuated. The species that survived left behind most of the competitors, predators and diseases of their original homes. Hawaii's many islands and diversity of habitats provided many vacant niches. Evolutionary shackles were well and truly released.

The evolution of many of Hawaii's birds was remarkable. The Hawaiian Honeycreepers (family Drepanidinae) evolved into over 50 different taxa from the descendants of only one original colonizing species. They covered the range of niches from nectarivore, granivore, insectivore to a bird that fed on palm fruits and another that specialized in snails! Some of the colours and bill shapes of the species are truly amazing.

Other groups represented by novel species included monarchs (Monarchidae), crows (Corvidae), thrushes (Turdidae), honeyeaters (Meliphagidae), geese and ducks (Anatidae), rails (Rallidae), hawks (Accipitridae), owls (Strigidae). They even had a flightless ibis (Plataleidae)!

Yellow flowering plant, restricted to the Alaka'i Swamp on the central plateau of Kaua'i.

BIOLOGICAL EXITS & ENTRIES

Many of 30-40 species known only from the subfossil record became extinct soon after the Islands were settled by Polynesians. Since the arrival of Europeans another 23 taxa have become extinct and many more are endangered. The extent of extinctions in Hawaii is stark- they make up only 1% of the United States landmass but they account for 75% of extinct species in the USA. The Polynesians brought fire, pigs, dogs and Polynesian Rats (Rattus pacifica) and agricultual development. Europeans brought goats, European pigs, sheep, cattle, horses, cats, Ship Rats (Rattus rattus) and Mongooses (to eat the rats).

Over 150 species of birds have been introduced to the islands from all corners of the planet. Some of these species are occupying natural ecosystems and competing with native birds. It is widely accepted that one of the major causes of bird extinction in the last 200 years has been the spread of the bird diseases Avian Pox and Avian Malaria. These diseases are believed to have come into Hawaii in introduced birds and spread by introduced mosquitoes. Many of the native birds have lost all resistance to these diseases. There are some positive signs though of resistance developing within the Hawaii Amakihi and Oahu Amakihi.

Many of the foreign birds are occupying unnatural ecosystems and unoccupied habitats (due to previous extinctions). There is no denying that that the diversity of world birds are now a feature of Hawaiian birding.

Red-crested Cardinal Paroaria coronata. One of the introduced birds. They are originally from Central America.