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Kaua’i is an extraordinary place to see seabirds. Kilauea National Wildlife Refuge on the North Shore hosts nesting Laysan albatrosses, red-footed boobies, and wedge-tailed shearwaters. The boobies occupy a wooded slope above the ocean; we watched them bringing in twigs as nesting material. The albatrosses, mostly unpaired adolescents and supersized chicks, use a nearby hill. Almost literally underfoot, the shearwaters had excavated burrows right at the edge of a paved path. Great frigatebirds, long-winged piratical creatures, nest elsewhere but come to Kilauea to steal fish from the hapless boobies.
With all that, I’d have to say that our most memorable seabird encounters involved tropicbirds. Two species breed in the Hawai’ian Islands, the white-tailed (koa’e kea in Hawai’ian) and the red-tailed (koa’e ‘ula). Tropicbirds are sleek, long-winged birds, somewhat like terns in appearance except for the pair of elongated feathers that extend from their tails. As you would expect, these streamers are red in the red-tailed tropicbird and usually white in the white-tailed, although we saw one individual white-tail with salmon-pink streamers. The red-tail’s feathers were used in traditional Hawai’ian regalia.
Although we saw red-tails only at Kilauea, we ran into at least a white-tailed tropicbird or two almost every day: in Waimea Canyon, near Poi’pu on the South Shore, at Wailua and ‘Opaeka’a falls on the east side. We watched them gliding above W. S. Merwin’s folding cliffs in the Kalalau Valley, in and out of the constantly moving fog. When a stray sunbeam hit them, their white plumage lit up.
Tropicbirds have traditionally been assigned to the order of birds that includes pelicans, cormorants, anhingas, gannets, boobies, and frigatebirds, with which they share totipalmate feet: all four toes connected by webbing. But a major phylogenetic study in 2008 grouped them in a lineage that included pigeons and doves, sandgrouse, grebes, and flamingos. Their fossil record is sparse, although 50-million-year-old remains in England have been attributed to a tropicbird or close relative.
Superbly adapted for flight, tropicbirds have small, weak legs and feet that are barely adequate for terra firma. “When they move short distances, they shuffle forward by pushing with both feet and falling forward on their bellies,” writes Craig Harrison in Seabirds of Hawaii: Natural History and Conservation. They don’t swim well either. But in flight they’re grace incarnate, turning and twisting to capture flyingfish, squid, mackerel scad, and sauries, or to evade a pursuing frigatebird. Red-tailed tropicbirds can pick off flyingfish on the wing.
Tropicbird courtship is aerobatic. We did not get to see the courtship flight of the white-tailed tropicbird, in which a pair glides in tandem, the male’s tail streamers touching the female’s back. However, we caught the red-tails’ performance at the Kilauea refuge: a half-dozen birds facing into the wind and back-pedaling so as to leapfrog their neighbors. This is accompanied by the strident vocalizations that led sailors to call them bosun birds, for the sound of the boatswain’s whistle.
The two species have different nesting habitat preferences. Red-tails lay their single egg under concealing vegetation on flat clifftops overlooking the sea. White-tails use crevices in inland canyons, often near waterfalls. Twice we watched a white-tail spiral down toward a cliff face and suddenly disappear into an undetectable cavity in the rock wall. These birds also nest on the rims of the still-active craters of the other Kilauea on the Big Island, about as predator-proof a site as you can imagine.
Both sexes incubate the single egg. Depending on site availability, red-tails can be loosely colonial, but they are far from neighborly.
Harrison says they have vicious tempers. Nestlings are sometimes killed during territorial battles between adjacent pairs. White-tail
nests are more dispersed, and much harder for biologists to reach.
A cultural sidebar: the annual Merrie Monarch hula competition took place at Hilo on the Big Island while we were on Kaua’i. (The monarch in question: King David Kalakaua, who helped rehabilitate the hula after its suppression by missionaries.) The winning group this year, Ke Kai O Kahiki, performed a tropicbird-inspired routine including a jumping move called kenapulu that evoked the birds’ diving maneuvers. You can see it on YouTube.
They did not, however, try to imitate the backward-circling dance of the red-tailed tropicbird. That’s something I would happily pay to see.