Issue 20.5: October/November 2017
Department

‘Iwa

The great frigate bird is a master thief, a harbinger of storms and the world champion of aerial endurance
Story by Brittany Lyte.

Upon unifying an archipelago of separately ruled islands into the Hawaiian kingdom in 1810, King Kamehameha was awarded an epithet likening him to a certain bird. He was called Ka‘iwakīloumoku, the ‘iwa that hooks the islands together. It was a pointed homage. ‘Iwa is the Hawaiian name for the great frigate bird, Hawai‘i’s largest bird. ‘Iwa is also the Hawaiian word for thief, a reflection of the bird’s strategy of snatching fish from the mouths of smaller birds—or in the case of Ka‘iwakīloumoku, snatching islands from other chiefs.

The ‘iwa appears in many traditional Hawaiian mo‘olelo and ‘ōlelo no‘eau, stories and proverbs. “Lele ka ‘iwa, māile kai ko‘o,” for instance, is a saying that means, “When the ‘iwa flies out to sea, the rough sea will be calm.” It is both a weather observation and a phrase that might be applied to, say, a disruptive person whose departure will restore tranquility. “Kīkaha ka ‘iwa he lā makani” means “When the ‘iwa bird soars on high, it’s going to be windy.” It is a saying employed when speaking of an attractive, smartly dressed person—someone whose appearance might cause a stir. When translated directly, “He ‘iwa ho‘ohaehae nāulu” means “An ‘iwa that teases the rain clouds.” This phrase can be used to call out a beautiful young woman or handsome young man who incites jealousy in onlookers.

The great frigate bird is found on remote, tropical islands in the Indian and Pacific oceans, with a subspecies of about ten thousand pairs nesting atop bushes in the uninhabited Northwestern Hawaiian Islands. Sightings are rare. The bird is seen in the main Hawaiian Islands only when it comes in to escape storms at sea. Indeed, its appearance in the main islands has long been a reliable predictor of bad weather. Most of the bird’s life is spent in flight, feeding on smaller fish found around schools of larger deep-sea fish, such as tuna, while traveling to places as faraway as Micronesia and the Philippines.

Among scientists, the ‘iwa has attracted attention for its amazing feats of flight. With its forked tail and seven-foot wingspan, it can soar great distances for months on end without landing, traveling up to three hundred miles a day. Though it’s a tropical bird, it routinely ventures to altitudes where the temperatures are frigid. And while it is a seabird, it can’t actually land upon the sea, for its feathers lack waterproofing. Unlike other seabirds, it is unable to feed below the ocean’s surface, lest it become waterlogged and drown. Instead, the ‘iwa feeds on the wing by snatching fish at the surface or by grabbing smaller birds in midair and shaking them until they disgorge their catch—the airborne piracy that earned the ‘iwa its Hawaiian moniker. “They just sort of shake the other bird until it throws up its meal,” explains Beth Flint, a wildlife biologist with the US Fish and Wildlife Service. “Sometimes the other bird will just throw up before the ‘iwa grabs it because they know it’s a battle they are going to lose.”

Frigate birds can soar above the sea for months on end, riding the thermals within cumulus clouds to conserve energy. They are found throughout the tropics and subtropics. The great frigate bird, pictured here, inhabits remote regions of the Pacific and Indian oceans, with a subspecies of about ten thousand pairs nesting in the remote Northwest Hawaiian Islands.

The frigate bird is the only species other than swifts that can stay aloft for months at a time. Although a juvenile frigate bird fledges in five to seven months, it typically depends on its parents for the first year and a half of life. After that, it will spend around 90 percent of its life in the air. How the bird achieves such prolonged flights without stopping to rest has long puzzled scientists. But new research has begun to uncover some of the ‘iwa’s secrets.

The frigate bird’s ability to remain aloft for weeks at a time is bolstered by a trick not known to be used by any other bird. It slips into billowy cumulus clouds like a stowaway, catching the updrafts streaming through the masses of water vapor. Rising as fast as sixteen feet per second, these powerful airstreams carry the bird to altitudes of up to two-and-a-half miles above sea level, where temperatures drop to freezing. The ‘iwa in this environment becomes free of the need to flap its boomerang-shaped wings. Soaring with the ease of a hang glider, the bird might even catch short bursts of sleep, despite the frigid temperatures. Having reached its peak altitude, it glides steadily downward until it finds the updraft of the next cloud in its path. Allowing air currents to boost them to higher altitudes makes the frigate bird highly efficient, able to cross large expanses of ocean in a zigzagging, roller coaster-like sequence of motion without expending much energy.

It seems like flying within the confines of a cottony cumulus cloud would be peaceful and serene, but it’s not. Cumulus clouds are hotspots of turbulence, making them shaky places for a three-pound frigate bird to hang out. Most other birds avoid clouds. Exactly how the ‘iwa withstands these high-intensity, low-energy flights, as well as the dramatic temperature shifts, is not yet understood. “It is believed to be very dangerous for a bird, especially one so fragile-looking as a frigate bird, to go inside of a cloud,” says ornithologist Henri Weimerskirch, who discovered the animal’s previously unknown practice of riding the clouds and co-authored a landmark study on the subject that was published in the journal Science in 2016. “Airplanes do not like to enter into large cumulus clouds, and yet frigate birds do it.” he says. “It’s really quite something.”

The frigate birds of the world are not easy to study. They spend most of their time aloft, and their breeding grounds tend to be on deserted islands or other hard-to-reach places. Furthermore, their migratory journeys to distant feeding grounds extend well beyond the range of most avian tracking devices. And if you enter a frigate bird breeding colony during the day, the birds will all fly away.

Over the last fourteen years, Weimerskirch, a scientist at the French National Center for Scientific Research in Paris, has developed techniques to overcome these challenges. Only recently, through his work, has it become possible to study the bird’s migratory movements in detail. Weimerskirch had previously been working with arctic birds, studying penguin breeding colonies and the impact of fishing boats on wandering albatrosses. In 2003 he decided to focus his attention on the tropics. He wanted to look at how frigate birds perform long migrations over oceans without landing and whether this behavior is learned or transmitted genetically to offspring.

Weimerskirch quickly learned that if he was going to work with frigate birds, he would have to do it stealthily. And that meant after dark. Using night-vision goggles, Weimerskirch and his team of researchers affixed solar-powered GPS trackers, as well as lightweight instruments that read heart rate and frequency of wing beats, to the tails of a few dozen birds. The ones chosen for Weimerskirch’s study were found in breeding colonies in New Caledonia, the Galápagos Islands and Europa Island, a low-lying atoll in the channel between Madagascar and Mozambique.

One juvenile bird in the study stayed in constant flight for a stretch of more than two months. Another flew a distance greater than the circumference of the earth. Over the course of its half-year journey, that bird rested for only a few hours at a time on just four occasions.

Although all frigate birds have the ability to make epic journeys, some populations are more prone to long-distance travel than others. Migratory behavior fluctuates between subspecies based on factors like weather, according to Weimerskirch’s findings. Of the five subspecies, frigate bird populations from Europa Island fly the longest distances, whereas Galapágos birds typically remain within the Ecuadorian archipelago throughout the year. Hawai‘i’s frigate birds have been known to undertake journeys of up to five thousand miles, but they are much more likely to travel within a tighter radius of the colony. New Caldonia’s birds fall somewhere in between.

So how does a young frigate bird know to ride the updrafts of clouds? Is it a learned behavior or a matter of instinct? And once it begins to ride an updraft, how does it withstand the turbulence and the freezing temperatures? These questions are central to Weimerskirch’s next study, in which he will use miniature body cameras to record bird’s-eye views of frigate-bird flights through the ever-changing sky.

In Hawai‘i, ‘iwa have continued to convey meaning for people in modern times. When the Honolulu businessman and industrialist Benjamin Dillingham opened a luxury hotel on O‘ahu’s North Shore in 1898, he wanted a name that captured its grandeur. So he called it Haleiwa, house of the ‘iwa. Set near the last stop at the northern edge of Dillingham’s sugar freight railway, the fourteen-room guesthouse was for nearly fifty years a pastoral, end-of-the-line retreat.

Although the development of Waikīkī and the advent of the automobile led to the resort’s demise, the high-end retreat opened the doors to modern tourism on the island’s rural North Shore. While the hotel is long gone, the community that surrounded it still carries the name Hale‘iwa. Today the seafood grill Haleiwa Joe’s stands along the bank of the Anahulu stream in its place.

‘Iwa continue to influence Hawai‘i’s culture and arts. Polynesian tattoo artists are frequently commissioned to do ‘iwa tattoos, which are said to symbolize survival and prophecies. Hawaiian fashion designer Sig Zane found that the birds in the sky created a natural pattern that translated perfectly onto his aloha shirts. When Lili‘uokalani Protestant Church in Hale‘iwa needed a new weather vane on its steeple, it replaced the rooster that had been there with an ‘iwa holding a fish in its mouth, referencing both the town and the Christian fish symbol.

Meanwhile, new scientific insight into the bird and its behavior, aided by satellite 
tracking devices, has reinforced the ‘iwa’s enduring power to spark inspiration. Sheila Conant, former chair of the University of Hawai‘i at Mānoa Zoology Department, who studied Hawaiian birds for fifty years, says the ‘iwa’s aeronautic agility continues to astonish observers—even more so now that scientists are slowly uncovering the mysteries of the birds’ flight. “I am amazed by their ability to fly and by their inability to walk on land,” she says. “I have seen them in the air, and they fly just so beautifully it takes your breath away. Then I have seen them on land and they just stand in place, totally out of sorts. They don’t walk, they just stand there. But soon enough they are jumping back into the air, where they belong.” HH