GPS loggers can give a bird's position to within a few yards. Some loggers also have temperature sensors. By attaching them to the legs of their study birds, scientists can tell when the birds are flying and when they are resting or feeding on the sea, because the water is generally cooler than the air.
As nifty as GPS loggers are, there is a snag: you have to get them back—an outcome by no means guaranteed. Among the larger albatrosses, chick-feeding forays can last ten days or more and encompass thousands of square miles of ocean. Lots of things can go wrong on these outings, particularly in and around commercial fishing grounds, where birds die by the thousands, done in by hooks, nets and the lines that haul them. And because albatrosses have to struggle to take flight in the absence of a breeze, birds may be becalmed on the sea.
On the Pyramid, Scofield was reasonably confident of retrieving his GPS devices. The Chatham albatrosses' feeding forays tend to be relatively short—only a few days—and there was little chance of his birds becoming becalmed in the windy latitudes they inhabit, meridians known to mariners as the Roaring Forties, Furious Fifties and Screaming Sixties. More worrisome to Scofield was the knowledge that the area adjacent to the Chatham Islands—known as the Chatham Rise—is one of New Zealand's richest commercial fishing grounds, replete with orange roughy and several other deep water species. Albatrosses, too, know where fish are found, and the birds sample the most productive fishing areas much as human shoppers make the rounds of favorite stores.
And what expeditions these birds make! From mollymawks, as the smaller species are known, to the great albatrosses, these super-soarers cover tens of thousands of miles in their oceanic forays. Individuals of some species circumnavigate the globe, covering 500 miles a day at sustained speeds of 50 miles per hour.
And then they somehow find their way home—even when home is an outpost in the ocean like the Pyramid, not much bigger than an aircraft carrier. At the start of their breeding season, albatrosses have been tracked making almost ruler-straight trips from distant foraging areas to their nests. Because the birds maintain their course day and night, in cloudy weather and clear, scientists believe they use some kind of magnetic reckoning to fix their position relative to the earth's magnetic field.
The birds also seem able to predict the weather. Southern Buller's albatrosses were found to fly northwest if a low-pressure system, which produces westerly winds, was imminent, and northeast if an easterly wind-producing high-pressure system prevailed. The birds typically chose their direction 24 hours prior to the arrival of the system, suggesting they can respond to barometric cues.
In his autopsy room in Wellington, ornithologist Christopher Robertson slit open a plastic bag containing a white-capped albatross. The swan-sized carcass had been thawing for several days. Along with dozens of other seabirds in Robertson's freezers, this one had been collected at sea for the government's fisheries science program.
Robertson carefully unfolded the bird's wings—wings that would have carried it halfway around the world, between its breeding grounds in New Zealand's Auckland Islands and its feeding grounds in South African seas.
The albatross bore a raw wound at the elbow. Its feathers and skin had been rasped down to bare bone, presumably by the thick steel wires—called warps—that pull a trawl net. Of the 4,000 albatrosses and other seabirds Robertson's group has autopsied over nine years, nearly half have been killed by trawl fisheries, which use giant sock-shaped nets towed at depths of a quarter mile to capture 40 tons of fish in a single haul. (Albatrosses and other large, soaring birds tend to die as a result of collisions with the warps, while smaller, more agile fliers such as petrels and shearwaters are more likely to get ensnared in nets—to be crushed or drowned—while feeding.) The finding has surprised the fishing industry and conservation groups, which have considered longline fishing—in which thousands of baited hooks are fed out behind the fishing vessel—a greater threat to seabirds.
There are no reliable figures for the number of birds killed per year through contact with commercial fishing operations, but estimates for the Southern Ocean are in the tens of thousands. Vessels in well-regulated fisheries are required to minimize their impact on seabirds and report any accidental deaths, but there is a large shadow fleet of illegal, unregulated and unreported (IUU) vessels operating outside the regulations, answering to no one.