It’s an `apapane party in the Kona unit of the Hakalau Forest Reserve. The bright morning sun glints off their pinkish-red bodies as they flit between `ohi`a trees. Their varied calls fill the forest. `Amakihi, `elepaio, and `i`iwi can also be heard, but they are harder to see. It is 8 o’clock in the morning on January 12, and at an elevation of one mile it is just beginning to get warm. As much as I would like to watch birds in the sunshine, it is time for me to climb into the darkness of one of the area’s many lava tubes. I am here with my mother and Donna Ball, a refuge biologist with the U.S. Fish and Wildlife Service, and we are about to go caving. The ground in front of us opens up into a large, gaping, sinkhole, about 40 feet wide and two stories deep. Like all the other sinkholes I have seen, it is beautiful. Wild cattle, sheep, and pigs cannot reach the vegetation, so it is more lush and diverse here than elsewhere in the forest.
Since gaining legal access in February of 2005 to the land it had purchased eight years earlier, the Fish and Wildlife Service has issued a special use permit to one scientist, allowing her to conduct research in the Kona unit. That scientist is my mother, Helen James, an avian paleontologist with the Smithsonian Natural History Museum. Throughout her career she has made many discoveries about the natural history of the Hawaiian Islands by analyzing the fossil birds she finds in caves. We hope to make some more discoveries today.
All sinkholes are not created equal. You can walk right into some of them, while others can be entered only by descending on rope. We can access this one easily enough by sitting for extra stability and then scooting down a narrow slope using convenient tree roots or trunks for hand and foot holds. This is particularly easy for us because we did it yesterday. We explored the tube makai of this entrance until we came to another opening, at which point it was time to head back to camp. We are interested in the cave beyond the second sinkhole, but are using this entrance because it is safer.
Once we reach flatter ground we don head lamps and begin to make our way down the steep jumble of `a`a lava that leads to the mouth of the cave. Forest noises fade into cave noises. The faint but constant dripping of water from the lava stalactites, and the soft crunch, crackle and scrape that three pairs of feet make when maneuvering over an `a`a floor echo back to us. We find ourselves speaking in hushed, almost reverential whispers.
We cross the ground we covered yesterday as quickly and safely possible, which is not very quick considering that the `a`a is often loose and tends to wobble or shift under foot, and the smooth pahoehoe is wet and slippery. With just one beam of light to illuminate my surroundings, I must look up, down, and to the sides frequently. When exploring a cave you’ve never been in before it is impossible to know what is more than twenty feet ahead of you. The next room could be large and cavernous, with a very high ceiling, or the passage may become so narrow that you have to take off your pack, push it through ahead of you, and slither through on your belly. Lucky for us, this cave never gets that small.
The original floor of the cave, where fossils are most likely to be found, can rarely be seen. In most places material has fallen from the roof, creating uneven hills. We scramble over these slopes, careful to ascertain that a rock will not move beneath us before we put weight on it.
Eventually, we come to the second sinkhole. I take my time crossing it. It is nice to see the sun and hear the birds for brief moment. When we get to the mouth of the next cave, we walk slowly, looking very closely at the gray floor. We expect the fossils to be a nice, contrasting brown color, like the petrel we collected yesterday. Mom quickly finds another petrel. Then I find one. I find two fossil rails close to each other and a rail skull with no other bones around it. Skulls are rare finds, because they are delicate and quick to decay in the moist cave climate. A predator, possibly a pu`eo, may have dropped the skull here hundreds of years ago.
So far, so good. Staring at the wall of the cave, I see a tiny, dark, cryptic shape that may be a bone. It is! Mom can barely see it so she asks me to collect it. Using small, pliant forceps I delicately gather the bones into a little plastic box filled with cotton batting. I excavate the surrounding rocks, hoping to find more of the skeleton. Moving the rock reveals a minute flake that may be part of the skull. I call Mom over, afraid that the moist, fragile bone will break when I touch it. The insignificant looking brown sliver means nothing to me, but for Mom it contains invaluable information. Farther into the cave we find a large pile of blond bones. A fossil of a moa nalo, a giant extinct fossil goose, endemic to the Hawaiian Islands, and a very exciting find. The bones we collect today will dry out and be shipped back to the Smithsonian where Mom will identify them and analyze their morphology and DNA. She will send tiny pieces to a radio-carbon dating lab to learn their age. From this information Mom will be able to learn more about the evolution of Hawaiian avifauna and the reasons that most of these unique species went extinct.
It’s been a good day for avian paleontology.
— Sydney Olson
Volume 16, Number 8 February 2006