Seabirds Lost and Found

By Joe Eaton
Wednesday September 07, 2011 - 09:29:00 AM
Probable Bryan's shearwater, Midway Island 1991.
Reginald David
Probable Bryan's shearwater, Midway Island 1991.

This has nothing to do with Berkeley, the Bay Area, California, or the continental United States. It’s about a species of bird I’ve never seen and that no one may ever see again; about the quirks of taxonomy and the unlikely places that scientific discoveries are made. 

In 1963 A. B. Amerson Jr., a scientist with the Pacific Ocean Biological Survey Program, found an odd bird in a burrow in a colony of Bonin petrels on Sand Island, part of the Midway group, in the outer Hawai’ian chain. It appeared to be a shearwater, one of a group of seabirds in the procellariform order. Procellariforms, which range in size from tiny storm-petrels to enormous alabatrosses, are sometimes called tubenoses, because of specialized tubular nostrils that allow the birds to drink seawater and excrete the salt. Shearwaters are midsized tubenoses, with 20-odd species plying the world’s oceans. Several species occur off the California coast; one, the sooty shearwater, in huge seasonal aggregations. 

The Midway bird, black above and white below with blue legs and a blue-gray bill, was identified as a little shearwater (Puffinus assimilis), a widely distributed species not previously known to occur in Hawai’i. In the name of science it was killed (one hopes humanely), skinned, transported to the mainland, and filed away in a drawer at the Smithsonian. 

There it lay until ornithologist Peter Pyle of the Point Reyes Station-based Institute of Bird Populations happened to examine it while researching a new book on Hawai’ian birds. Pyle said he realized at once that the bird was not a little shearwater “or anything else that occurred in the Pacific Basin.” He referred the specimen for genetic analysis by Robert Fleischer, director of the Smithsonian Conservation Biology Institute’s Center for Conservation and Evolutionary Genetics, and SCBI predoctoral fellow Andreanna Welch. 

Pyle, Fleischer, and Welch reported in an article just published in The Condor ( that the Midway shearwater was genetically distinctive and had most likely diverged from its nearest relative at least 2 million years ago. The authors christened it Bryan’s shearwater (P. bryani) after Pyle’s grandfather Edward Horace Bryan Jr., long-time curator of collections at the Bishop Museum in Honolulu. 

That’s pretty extraordinary when you think about it. Scientists are still finding a steady trickle of new bird species, but most come from tropical forests in places like Peru and Cambodia. Hawai’i, even its northwestern islands, has been gone over thoroughly. The last new discovery there was a small songbird called the po’ouli, 

first detected in 1974 (and extinct by 2004, when the last known individual died in captivity.) 

Although classified in the genus Puffinus, the shearwater is no more a puffin than you, the reader, are a gerbil. Puffins are alcids in the genus Fratercula. Go figure. 

Pyle et al note that Bryan’s shearwater is morphologically similar to Boyd’s shearwater (P. boydi), which nests in the Cape Verde Islands off northwest Africa and was formerly considered a subspecies of the little shearwater. Shearwater taxonomy seems to be in flux. 

Where has the bird been all this time, both before the demise of the type specimen in 1963 and afterward? There’s another sight record from Midway in 1991-2 and some possible encounters at sea as recently as 2005. Shearwaters as a group are notoriously hard to identify under optimal circumstances, let alone from a pitching boat in bad weather. Some may have been passed off as out-of-range little shearwaters, or other similar tubenoses. 

Its former (and present, if it isn’t extinct) range remains a mystery. Pyle doubts that it nests, or nested, in the Northwestern Hawai’ian Islands. The two Midway birds may have been just prospecting. The species could have bred anywhere in the Pacific. 

Ironically, the Midway individuals might have been among the last of their kind. It’s plausible that Bryan’s shearwater was part of the collateral damage from the human settlement of the Pacific islands. 

The expansion of the Lapita people and their Polynesian descendants into the South Pacific is one of the great human epics. Like starship voyagers heading for another solar system, whole communities of islanders loaded their dogs, pigs, chickens, taro, and coconuts into double-hulled canoes and set out for the unknown, navigating by the stars and currents and the behavior of seabirds. Some, like the settlers of Easter Island and New Zealand, wound up in places they couldn’t get back from. 

Recent archeological research shows that those oceanic pioneers were responsible for the extinction of hundreds of bird species: at least 2000 by one estimate. The large, flightless, tasty ones like the moa of New Zealand and the gooselike moa-nalo of Hawai’i were hunted for food (“moa” means “chicken” in most Polynesian languages.) No one realized they were destroying a species; who was to know that there weren’t more of the same on the next island, or the next? 

Seabirds and their eggs were also prized. Smaller landbirds lost their habitat when island forests were cleared for farming. The descendants of those pigs and dogs, along with stowaway rats, did in some ground-nesting birds. 

Then, of course, came LaPerouse and Cook, more livestock, more rats, cats, the sandalwood trade, sugar plantations, World War II, and beach resorts. The last few centuries took their toll on additional bird species that had survived the first human impacts. 

I would be pleasantly surprised if Bryan’s shearwater escaped the fate of the po’ouli; if someone found a nesting colony on some isolated atoll. I wouldn’t count on it, though. At least now we know it was there.