The Kingdom of Rarities (5 page)

Top: map of the island of New Guinea and environs; bottom: locations of Wallace's Line, the Sunda Shelf, and the Sahul Shelf

Bruce's expedition to the Foja Mountains held out the promise of enabling us to assess the accuracy of how rarity in relation to abundance is commonly portrayed in natural tropical habitats—a few abundant species and lots of others represented by a few scattered individuals or small groups. Perhaps absent humans, especially local hunters, a different pattern would emerge from his team's observations in virtually undisturbed terrain.

Bruce's New Guinea team assembled in Jakarta, Indonesia's capital, in early November. On November 12 they flew from Java to Jayapura, the capital of Papua Province and the city nearest to the Fojas. During the ensuing three days of cutting through red tape with provincial bureaucrats, Bruce dealt with a new worry. Before arriving in Papua, he had been unaware that helicopter service was so scarce; transport might not be available to lift the team in. To come this far only to lose the sole mode of access to the summits would be a cruel blow.

As his colleagues grew restless, Bruce managed with great effort to secure a helicopter, only to encounter another restriction. The permits limited the expedition to a rapid assessment. The company could offer transport for only two specific days:
in
on November 22 and then
out
on December 7. The team would have to work fast and under pressure.

In the first stage of the expedition, they flew by small plane to a foothills airstrip in the Kwerba homeland. There they spent a week exploring the steep lower Fojas, collecting specimens, and planning the next leg. On November 21 they packed carefully and prepared for the helicopter to lift them higher up the mountains. Torrential rains marred the evening and increased the fear that their helicopter would be grounded on the following day. Bruce and Steve decided to split the overall expedition into two teams. The hill-forest team would take a short hike from Kwerba and explore the lower slopes. Bruce would lead the helicopter-mountain team. “No problem in splitting the group, as many do not want to go in helicopter into
high mountains . . . (not safe),” he wrote in his field journal, the short parenthetical postscript capturing the fears that went unspoken.

When their transport arrived at 9:30 a.m. on November 22, a few team members immediately set off with Bruce and the pilot into a heavy mountain cloud. They looked out the window in vain for their intended “landing spot,” a boggy lakebed. Not the ideal helipad, but a rare patch of flat earth amid the rugged mountains. In the fog, however, they couldn't see a thing. During twenty minutes of searching, the anxiety levels on the chopper climbed steadily. After a few more turns with no visibility, the pilot opted for an instrument landing and located the site using the global positioning system (GPS). The cloud opened just as he lowered to drop them in.

Some tree kangaroos lounging in the branches noted the noisy intrusion, if not its significance. The men now unloading boxes of camping gear represented the largest-ever group of scientists and possibly the first humans to walk on this spot, 1,650 meters above sea level. The most ecologically important reading was not the altitude, however; it was the distance from the nearest village: a two-week trek. Three additional runs, navigating the ever-increasing cloud on the mountaintop, brought in the rest of the helicopter-mountain team. The final run, carrying much of the botanical and mammalogical field equipment, did not make it in because of the weather. The team would have to do without.

To the newcomers, the absence of old campfires and forest trails—signs of hunters at work—was encouraging. The two headmen from the local Kwerba and Papasena tribes accompanying the expedition were as astounded as the biologists at how isolated the place was. As far as they knew, no one from either clan had ever been here. Perhaps birds of paradise, bowerbirds, tree kangaroos, and spiny anteaters—the species that Bruce and his colleagues hoped to see, on the basis of Bruce's previous work and Jared Diamond's reports—would still thrive here. These were the species that would offer clues about the patterns of rarity and abundance among closely related species, especially in the absence of humans.

Setting up camp in the forest by the bog dispelled some of the landing jitters, and any lingering fright soon gave way to elation. The first afternoon, as Bruce marked trail routes for animal surveys, a song from the forest suddenly stopped him in his tracks. He could barely contain his joy. He had just heard the call of the black sicklebill, a bird not expected to be in the Fojas. One of the most soughtafter birds of paradise—a glossy black creature with a sickle-shaped bill, red irises, and a saber-like tail—it is also the most difficult of its family to see in the wild.

The challenges of the landing and the potential for imminent new discoveries propelled everyone on the team to begin pursuing their specialties, assisted by graduate students from The State University of Papua (UNIPA). Steve Richards, the herpetologist, expected a welcoming chorus of new frog species. Kris Helgen was eager to see which species of tree kangaroos and other rare mammals awaited him. Wayne Takeuchi readied his plant presses for a bonanza of new species. Brother Henk van Mastrigt gathered his butterfly nets. Bruce focused on birds.

The next morning's first sighting bolstered Bruce's earlier prediction that the Fojas were probably high enough and expansive enough, and certainly isolated enough, to be a source of many new discoveries. Right in camp, a bird appeared that looked like a new species of honeyeater. The black, grackle-sized bird sported a face mask of extensive orange wattles. When the wattles became engorged with blood, the honeyeater looked as if it were blushing. The features failed to match any of the species Bruce and Thane Pratt had described or Dale Zimmerman had illustrated. This unique bird, later named the wattled smoky honeyeater, became the first new avian species discovered in New Guinea in fifty-four years.

The last described bird species in New Guinea had been the long-bearded honeyeater, discovered in 1951 by E. Thomas Gilliard on Mount Hagen, another isolated mountain peak. Among the vertebrate hunters, ornithologists have now been almost everywhere on the planet. The Fojas may be unique in being uninhabited
and untrammeled, but they join many other tropical mountain ranges in supporting rare species restricted to a single mountaintop or range. Biological expeditions to other parts of New Guinea and to New Caledonia, the Andes, Mount Kinabalu, the Eastern Arc Mountains of Tanzania, and the Annamite Mountains of Vietnam have time and again discovered new species on tropical peaks.

To understand this phenomenon—how species evolved into new forms in mountainous regions—evolutionary biologists and rarity specialists need to summon their inner geologist. In the Annamites of Vietnam, in Hawaii, in any place of volcanic origin, or where Earth's plates have shifted, the causes of rarity in tropical landmasses can go back eons.

New Guinea's geologic history is one of great complexity, and the birth of the Foja range illustrates this point. It all began with tectonic plates, the unevenly shaped floating slabs of rock that sit under the continents and oceans. Tectonic plates trace back to the early formation of planet Earth, almost 5 billion years ago, and their motion has been compared to that of slow-moving bumper cars—colliding, separating, colliding again and remaining stuck together—with the movements causing the continents to drift. When they collide, new landmasses arise. Less than a million years ago, ongoing contact between the Australian and Pacific tectonic plates uplifted deep seafloor material. From the collision of the two plates, the Fojas were born and rose rapidly (by geologic standards) out of the ocean. This uplift became an isolated landmass and attracted mountain-dwelling species from adjacent mountain ranges. Over cycles of cool and warm climate, mobile species from the high cordillera to the south that runs the length of New Guinea were able to colonize the newly rising Foja Mountains and other isolated ranges. Once settled on this recently uplifted chain, these populations of plants and animals were slowly carried upward into the mists as the mountains inched higher year by year. In isolation from others of their species and through the process of evolution by natural selection, these populations evolved unique traits.

This uplift created the series of mountain islands where species evolved, resulting in changes in some aspect of their appearance from the first arrivals. The geologic account reinforces a near-immutable law of rarity: the isolation of tropical mountain ranges leads eventually to the creation of new species and, in turn, drives patterns of rarity. This is because—by definition—when one species diverges from another in an isolated habitat, it often starts out as rare in terms of its narrow range. In some cases, a collision of continental plates may cause uplift that separates one widespread, abundant species into two populations, which may diverge. In general, however, many species on tropical mountains lack the dispersal capability to rejoin their former populations. Even tropical birds that could fly over the mountains tend to avoid such flights if it means leaving the altitudinal belt in which they are most accustomed to live.

Bruce's field journal included a most-wanted list. Truth be told, the expedition was for him an intensely personal pursuit of a quest species, the golden-fronted bowerbird, endemic to the Fojas. It was a dream shared by many. This species had not even been described until 1895, when Lord Walter Rothschild identified it from trade skins collected by locals from somewhere in western New Guinea. The discovery inspired many naturalists to search for the bird, but over the following eighty-two years all returned from their expeditions without success. Consider this entry by Michael Everett in his book
The Birds of Paradise and Bowerbirds
, published more than three decades ago: “Nothing is known of the Golden-fronted Bowerbird, except for what can be learned from only four known museum skins, all males . . . it has never been found in the wild . . . and among bowerbirds or birds of paradise is unique in this respect. It may be either a very rare bird or one which is virtually extinct—but it is certainly one which has a very restricted range.”

The bowerbirds must have been eavesdropping. The next day, the team found several display bowers of this elusive species close to camp. According to the
Oxford English Dictionary
, a bower is “a pleasant shady place under trees or climbing plants in a garden or
wood.” The bowers these birds construct are remarkable, fashioned from moss and sticks and decorated with blue and yellow fruit. The males spend hours each day vocalizing from perches in the saplings beside their bowers, often imitating the songs of other birds as well as other natural sounds. At the sight of the bowers, Bruce felt elated at the prospect that his quest might soon be realized. Now if they could just see the bird!

The next day, while marking survey trail routes through the forest with colored flagging tape, Bruce stumbled upon a male in attendance at a bower. The first encounter took his breath away. The robin-sized male sports a brilliant bonnet of yellow feathers, a look emulated by some New Guinea tribal chieftains who fashion the feathers into headdresses. When the yellow feathers are erected during its mating dance, the bowerbird is one of the most compelling sights in nature.