Last month a bunch of bird people were in Hilo. They attended the 67th Annual Meeting of the Coopers Society. The Coopers Society publishes The Condor, one of the prestigious journals for ornithological research. Professional researchers, government officials, land managers, and conservationists all came to network, hear presentations on new research, and do some birdwatching. For the general public these meetings and presentations were generally of little interest. The talks were loaded with feathery techno-speak and genetic jargon. There was no local press or media to capture the deliberate and painstaking news that came from behind the lecterns at the Hilo Hawaiian. Nevertheless, amidst the slides, overhead transparencies, and statistical graphs were some bone rattling ideas of Hawaii’s natural world.
Two participants at the meeting were Helen James and Storrs Olson. Among other things, they study bird fossils from Hawaii. Now these are not petrified fossils like the romantic dinosaur digs. These are primarily bird bones found in archeological middens, beach areas, and lava tubes. Both of these scientists, associated with the Smithsonian Institution’s National Museum of Natural History, construct a dismal view of Hawaii’s ecological past with their bones. “Hawaiian ecological communities have undergone dramatic changes since the arrival of humans,” James writes. She argues that at least half of Hawaii’s land birds are extinct. Storrs Olson thinks that the extinction rate for our birds may approach 80%. This paleontological perspective, according to Olson, takes some fundamental ideas down the drain.
One idea down the tubes is the idea of the eco-friendly Polynesians. Fossil evidence suggests a significant Hawaiian impact. Once the Polynesians arrived in Hawaii, they began to do two things to the birds here. First off, they ate an awful lot them. In the archeological garbage pits of Hawaiians past are numerous bird bones. Native bird bones dominate the earliest sites. As time progresses there are less and less native bird bones in the middens and more and more Polynesian introduced food sources such as dog, pig, and chicken. These pits show several extinct species of flightless land birds and numerous species of seabirds. Secondly, the Hawaiians cleared vast areas of lowland forest habitat with agricultural plantings, firewood gathering, and burning for grassland cultivation. This loss of habitat drove certain birds to extinction and many others were forced into marginal areas.
While the fossils reveal a remarkable number of extinct land birds, there seems to be only one extinction at the species level for seabirds. However, the numbers of seabirds has been reduced dramatically, with entire populations disappearing, not just in Hawaii but throughout Polynesia. The seabirds in the Pacific at one time numbered in the many millions and they migrated great distances. Olson argues that an intimate connection between human culture and the seabirds existed. The huge columns of migrating seabirds from archipelago to archipelago in the Pacific, a literal stream of birds, provided the Polynesians with an automatic guidance system of navigation. Following the birds, they discovered the islands. As they ate the birds, their navigation system was lost. The dramatic decline of seabird populations in the fossil record coincides with the end of Polynesian back and forth migration. At about the time the Hawaiians lost touch with other Polynesian cultures, vast amounts of seabird fossils disappear throughout the Pacific.
Another idea shaken by the bones is the makeup of the pristine, native Hawaiian ecological communities. All of the common forest birds found today in Hawaii are nearly absent in the fossil record. Notably rare are the nectar eating honeycreepers such as Iiwi, Apapane, and Amakihi that dominate the native forests today. Instead, the fossils show an abundance of birds that currently are exceedingly scarce or extinct like the Kioea, which is found commonly in the lava tube fossils of Kona. Another cave find was the herbivorous, giant, flightless goose, the Moa Nalo, found in Umii Manu, or bird trap. This lava tube, discovered in 1992 by biologist Jon Giffen on the slopes of Hualalai, contained hundreds of bird skeletons including the oval-billed Nukupuu, specialized at excavating insects from tree limbs and trunks and, the giant akialoa, the largest honeycreeper yet discovered. According to the fossil evidence, the Hawaiian forests were dominated by seedeaters, herbivores, specialized insect eaters, and predators like the sea eagle, harrier, and long-legged owl. The Nihoa Millerbird and the Laysan Finch though now restricted to Nihoa and Laysan respectively, were found in fossils throughout the main islands. Likewise, the Laysan Duck and the Gallinule, coastal wetland birds today, were found at high elevations on Maui and Hawaii Island. Many species in historic times that are known from specific locales, habitats, and islands have been discovered in many different areas. So far over three dozen new species of Hawaiian birds have been found in the fossil aviary. The bird bones tell of a dramatic transformation in Hawaii’s forests.
The fossil evidence begs the point, Olson says, as to what plant species composed the forest communities? If there were different bird population communities eating different food sources, where did that resource come from? Perhaps, the nectar producing Ohia-lehua tree did not dominate our forests as it does today? Perhaps, the pre-human Hawaiian forests were altogether different communities than we know at present? If so, then a forest that today is completely made up of native plant species and appears to be “pristine,” is really a forest that has been fundamentally altered by the arrival of humans. Among Hawaiian biologists, conservationists, and environmentalists, you can be sure amidst that pile of thought, they have a bone to pick with Olson and James.