Climbing to the hornbill’s realm – bird observations – Cover Story
Tui De Roy
High in the canopy of Sulawesi, our roving editor observes that when figs ripen, red-knobbed hornbills go berserk.
Quietly we pad through damp leaf litter on the stately rain forest floor of coastal Sulawesi, one of the northern islands in the vast archipelago that makes up the Republic of Indonesia between Southeast Asia and Australia. The musty smell of a myriad invisible rain forest organisms, from fungi to forest pigs, mingles with the sweeter scents of fruit, flowers and foliage in the canopy 50 meters (150 ft.) above. Streaks of hot tropical sunshine slant down through windfall gaps, illuminating giant buttress roots and setting off the first of the morning’s ear-splitting concert of cicadas.
Suddenly harsh barking erupts overhead, like an angry guard dog coursing through the sky, unseen beyond the foliage. We freeze. “Hornbills!” whispers my friend Margaret Kinnaird, field researcher for the New York based Wildlife Conservation Society. “You can hear the two-tone bark, a pair calling in cadence. They’re probably heading for a fruiting fig tree.”
As the huge birds pass just above, their calls make way to an even more startling sound: Woosh-woosh-WOOSH-WOOSH-WOOSH-woosh…like a steam engine. Unbelievably loud, the noise stems from an aberration in hornbill wing design. Unlike all other birds, hornbills lack underwing coverts, those streamlining feathers which cover the base of the flight feathers and allow for smooth airflow. Instead, the wind rushing through the gaps in a hornbill’s wings is so loud it can be heard up to 200 meters (some 65 feet) distant.
Awestruck, we resume our walk uphill in the direction taken by the hornbills. Soon more wooshing and barking ring out in the distance. As we approach a particularly large, gnarly tree, an explosion of sound jolts the air and nearly makes us duck. Flashes of black wings, white tails, orange beaks and red, blue and yellow heads sparkle through the canopy as 30 or more huge startled birds take off in all directions far above. I have been dreaming of this moment for years: My first sight of the Sulawesi red-knobbed hornbill, a bird found only in this orchid-shaped island just south of the Philippines. I know immediately that I must find a way to share their treetop world, something no photographer has ever done before.
There are 54 species of hornbills worldwide, ranging from the dry savannas of Southern Africa through India and the lush forests of Southeast Asia westward to New Guinea and the Solomon Islands. Although ranging in size from a turkey to a dove, all share absurdly large bills which they use like forceps to pluck their food. At 2.6 kilograms (about 6 lbs.), the red-knobbed is one of the larger types–and certainly one of the most stunningly colored. For the last four years Margaret and her husband Tim O’Brien have been studying the ecology of a tiny remnant tract of lowland tropical rain forest set aside by the Indonesian government as the Tangkoko-Duasadara Nature Reserve. Surrounded by a sea of coconut plantations and fishing villages in the populous northern reaches of the island, the reserve covers a mere 8,867 hectares (34 sq. mi.) yet harbors a remarkable density of wildlife.
The lives of many of the animals here revolve around figs and a curious rain forest phenomenon: that one at a time, individual fig trees burst into fruit, attracting a parade of feeders. A tree may fruit only once every year or more, when upwards of 100,000 juicy figs ripen within just a few days of each other. Rich in calcium and carbohydrates, the figs range in size from tiny pink myrtlelike clusters to red-orange fruit shaped like small plums.
Secretive canopy-dwelling pigeons and doves, parrots and parakeets and a whole tribe of mynah species in strident multitudes flock to this bounty. Two types of little-known marsupial cuscus–one active at day, the other at night–join in, along with noisy troops of black macaques. Within two or three days they will strip a tree bare and the feeding frenzy will move on.
Of the many fruit eaters Tim and Margaret have analyzed, the red-knobbed hornbill is probably most central to the forest ecology. It stands out as a remarkable disperser of rain forest trees, regurgitating large seeds from the fruits it has eaten and passing smaller ones unaffected through its droppings.
By painstakingly capturing wild birds in the canopy and fitting them with radio transmitters, Margaret and Tim have found that hornbills may fly up to 30 kilometers (19 mi.) in search of food, even locating isolated wild fruit trees along roadsides or in agricultural plots. Hornbills can therefore be regarded as the lifeblood of a healthy forest, regenerating it and helping to support the other species which depend on it.
All these facts go through my mind as I listen to the birds above me already flocking back to their feast of figs. The ground where we stand is littered with thousands of round red fruits, knocked down by the hubbub of activity above. If only I could get myself up into those laden branches, what an amazing sight this would be.
Fortunately for me, Margaret and Tim have already tackled the tricky art of ascending giant rain forest trees. My partner Mark Jones and I decide to spend the next two months learning their secrets. Every morning before daybreak, we head into the forest, slinging climbing rope and hardware over one shoulder and camera gear over the other until the calls of hornbills and monkeys lead us to a just-ripening fig tree.
Then begins the arduous process of climbing. To start this trial-and-error effort that takes many days to master, we tape a hundred meters (330 ft.) of fine kite string to a weight and load it into a slingshot. I aim meticulously between tier upon tier of overlapping foliage, only to watch helplessly as my precious projectile bounces off tree trunks or careens out of control through dark thickets. Sometimes, the string wraps itself irretrievably around the viciously hooked spines of rambling rattan palms. My muscles ache. Then at last a lucky shot. The weight and string sail over a sturdy branch and back down to the ground. We quickly attach a parachute cord to the lightweight string and haul it up, repeating the process with a still-heavier climbing rope. At last, with harness and safety straps buckled on, I’m ready, and my clips and carabiners, rope ascenders and descenders all clank around my waist and chest. I depart the ground with barely containable excitement. Spinning round as the rope stretches, I feel like a spider dangling from her gossamer thread. I tell myself not to look down.
Slowly I emerge into another world, a setting where gravity is something I’d rather not think about. With a mixture of elation and trepidation, I realize I am entering the realm of the magnificent hornbill. Nearing the 30 meter (100 ft.) level, I finally pause to look around. I have left the gloom of the forest floor now, as if the clock had suddenly skipped from early morning to mid-day. It is hotter and drier here, too, the foliage around me dense and brilliant green, not dark and dank anymore.
But when I reach my destination at 36 meters (120 ft.) disappointment awaits me. A few withered, rotting figs and dropping-splattered leaves tell me of the departed flocks of hornbills which have long since moved on to more bountiful restaurants. Only the hum of sweat bees and blood-thirsty midges breaks the silence. Clearly I am too late for action in this tree. Days and weeks follow. With practice, we get better at gauging the “climbability” of individual trees, quicker at setting up ropes. Tiny mites infest our clothing as we work on the forest floor, swarms of attacking canopy ants scramble down the ropes to meet us, tangled branches need sawing off at arm’s length while dangling in mid-air, and heavy rain showers knock down ripe fruits and prevent climbing on slimy ropes.
At last one fine morning I find myself tucked into my tiny green nylon blind 40 meters (135 ft.) above ground by the time the first golden sun rays caress the crown of a large fig tree in front of me, its branches laden with purple- ripe fruit. Mark has helped me hoist my camera bag and tripod, now securely strapped to my tree, and departed on his own photo forays elsewhere in the forest. My perch is comfortable as treetops go: two 20 centimeter (8 in.) horizontal branches above each other allow for both seat and secure foot rest. As I look down the trunk of my tree, I realize an imperceptible breeze is causing it to twist and sway, reminding me of what an ant must feel gazing down a wet noodle.
My reverie is rudely interrupted by loud Aarf, aarf, aarf swooping in behind me. As great sweeping wings woosh so close I feel they are going to knock me off my perch, I watch a pair of hornbills in breeding colors land in my narrow field of view. Both male and female share black bodies, long white tails, intense blue faces and brilliant orange, scythe-shaped bills. As if this gaudy color arrangement is not enough, the male adds a bright red beacon to the knob on his head, and yellow and rufous neck feathers. The female shared his colors when younger, but by the end of her first year, she has changed to slightly more humble hues.
Being the first hornbills at the tree this morning, this pair takes careful stock of the surroundings. Perching very still, the birds lower their heads and scan the view slowly, long eyelashes batting. More barks announce other arrivals, mostly in pairs. Soon the tree is alive with big birds hopping heavily about, systematically plucking juicy fruits and knocking them back one by one into cavernous beaks. When the hornbills can eat no more, they continue loading more fruit into pendulous throat pouches of bare, powder- blue skin for later consumption.
As the suffocating heat of noon brings a lull to all rain forest life, many hornbill pairs settle on shady inner branches of the fig tree, mates quietly preening each other or showing off by raising their long spiky head feathers. Occasionally a male rolls intact fruit from his pouch into the tip of his long beak and passes them daintily to his mate, who accepts with satisfied groans.
This gesture serves to reinforce a lifelong devotion to her and signals he is willing and able to provide for all her needs and that of their offspring during the coming months. Soon she will incarcerate herself willingly into a deep tree cavity which she uses every year, using crushed fruit and her own droppings to cement an adobe-hard door with only a narrow slit for her mate’s faithful food deliveries.
All day I sit motionless, mesmerized by the insights I am getting into the hornbills’ private lives. Though they are mostly quite sociable, I see two males clash with open beaks, perhaps accounting for the unexplained chips often seen on their bills. Only when the brief tropical dusk descends on the forest, and I have long since shot every last roll of film, do I slip down my rope and walk the two kilometers (about 3 mi.) back to base, stiff-jointed but heart glowing.
The hornbill’s nesting season is well underway by the time we prepare to leave Sulawesi. I watch one female through the tedious work of sealing herself into her nest hole. For hours she builds up the layers of fruit-based mortar to narrow down the entrance. When it is almost closed, she squeezes her head and shoulders out and takes one long, lasting look at the surrounding forest, staying motionless for a whole hour before resuming her task. Here she will lay and incubate her eggs, keep the nest clean, protect the chick and molt all of her tail feathers. Then one day, after three to four months confinement, she’ll knock open her door and escape to the plentitude of figs awaiting her in the forest treetops.
Roving editor Tui De Roy and partner Mark Jones took time out between trips to the Galapagos and Antarctica to spend two months pursuing hornbills for these photographs in Indonesia.
High in the canopy of Sulawesi, our roving editor observes that when figs ripen, red-knobbed hornbills go berserk
LEARNING THE ROPES, author Tui De Roy dangles along the trunk of a rain forest giant in Tangkoko-Duasadara Nature Reserve in Sulawesi. Once she got the hang of climbing, De Roy was able to photograph red-knobbed hornbills as they gorged on figs.
JUGGLING a ripe fig like a marble, a male hornbill in full breeding colors downs dinner (far right). The oversize beak is used like a forceps to sort unripe red fruits from ripe purple ones. The length enables the hornbill to extend its reach without changing perches. A male (preceeding page) rolls ripe figs from a throat pouch to his mate sealed in a tree with their young.
WITH WINGS BEATING as loudly as an approaching steam engine, a male hornbill cruises over the high canopy in search of fruiting fig trees. Hornbills lack underwing coverts. This design allows air to rush between the birds’ flight feathers, producing the unusual sound. Seeing the birds is more difficult than hearing them, and the only place to get photographs is from dizzying treetop heights.
PEERING FROM HER NEST entrance, a female takes a last look at the world outside the hollow tree in which she will seal herself, free of predators, to hatch her young. She cements herself in using her own droppings and fruit from her mate.
LONG EYELASHES BATTING, a male hornbill perches in a fruiting fig tree to look for food for his nesting mate. Young females at first share the same brilliant colors as males, changing to more sober shades of black after their first year.
Fig trees drive the rain forest community on Sulawesi. Each species of fig is pollinated by a minute dedicated wasp which lives and breeds inside the fruit. In turn, figs feed an army of mammals and birds which disperse the seeds. Black macaque monkeys might strip a tree bare of ripe figs at one sitting, while on the forest floor, herds of snuffling Sulawesi bush pigs suck up dropped fruit like vacuum cleaners. Of the many fig-eating birds, hornbills are especially active dispersers, ferrying seeds over long distances as they fly between isolated remnant woods.
COPYRIGHT 1996 National Wildlife Federation
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