The Amazing Albatrosses
Posted by sky | Tags: Animals, GPS, Photos, Science, Technology, bird, extinction, natural-selection, nature, wildlife
From Smithsonian by Kennedy Warne.They fly 50 miles per hour. Go years without touching land. Predict the weather. Mate for life. And they're among the world's most endangered birds. Can albatrosses be saved? Scofield, of New Zealand's Canterbury Museum and co-author of Albatrosses, Petrels and Shearwaters of the World, has been studying albatrosses for more than 20 years. To research these birds is to commit oneself to months at a time on the isolated, storm-lashed but utterly spectacular specks of land on which they breed. All but 2 of the 21 albatross species recognized by the International Union for the Conservation of Nature are described as vulnerable, endangered or, in the case of the Amsterdam and Chatham albatrosses, critically endangered. The scientists hope that the data they gather may save some species from extinction. Scofield said. He and Moniz were planning to stay three weeks on the Pyramid (a storm-swept rock in New Zealand's Chatham Islands), and they hoped to deploy the popsicle-size GPS logger—tracking devices on a dozen breeding adults to track their movements at sea. Albatrosses are masters of soaring flight, able to glide over vast tracts of ocean without flapping their wings. So fully have they adapted to their oceanic existence that they spend the first six or more years of their long lives (which last upwards of 50 years) without ever touching land. Albatrosses can plunge into only the top few feet of the ocean, for squid and fish. The lengthy albatross "chickhood" is an adaptation to a patchy food supply: a slow-maturing chick needs food less often than a fast-maturing one. (Similarly, the prolonged adolescence—around 12 years in wandering albatrosses—is an extended education during which birds prospect the oceans, learning where and when to find food.) The chick's nutritional needs cannot be met by a single parent. Mate selection, therefore, is a critical decision, and is all about choosing a partner that can bring home the squid. In Buller's albatrosses the search for a partner takes several years. It begins when adolescent birds are in their second year ashore, at about age 8. They spend time with potential mates in groups known as gams, the albatross equivalent of singles bars. In their third year ashore, males stake a claim to a nest site and females shop around, inspecting the various territory-holding males. "Females do the choosing, and their main criterion seems to be the number of days a male can spend ashore—presumably a sign of foraging ability," says Stahl. Pairs finally form in the fourth year ashore. Albatross fidelity is legendary; in southern Buller's albatrosses, only 4 percent will choose new partners. In the fifth year, a pair may make its first breeding attempt. Breeding is a two-stage affair. "Females have to reach a sufficiently fat state to trigger the breeding feeling and return to the colony," says Paul Sagar of New Zealand's National Institute of Water and Atmospheric Research. "When they are back, the local food supply determines whether or not an egg is produced." Because it takes so long for the birds to produce a chick, albatross populations are keenly vulnerable to threats on their breeding islands. Yet the most pernicious threats to albatrosses today are not to chicks but to adult birds. This is not just because of the efficiency of modern fishing practices but because fishing equipment—hooks, nets and trawl wires—inflict a heavy toll of injury and death. John Croxall, a seabird scientist with the British Antarctic Survey says, knowledge of the birds' distribution at sea and their foraging patterns is "critical to their conservation." 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. 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. 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. 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. However, there is some evidence to suggest that fisheries may benefit albatross populations: a ready supply of discarded fish reduces competition for food between and within albatross species and provides an alternative food source to predatory birds such as skua, which often attack albatross chicks. In albatrosses—long-lived, slow-maturing species that produce a single chick every one to two years—the long-term negative impact of adult death far outweighs the short-term benefit of chick survival. It may take three, four or even five successful chick rearings to compensate for the death of just one parent, says Stahl. He calculates that "even small increases in adult mortality can wipe out the benefit of tons of discards fed to chicks." One albatross population that has unashamedly been propped up is the colony of endangered northern royal albatrosses at Taiaroa Head, near the city of Dunedin, on New Zealand's South Island. Taiaroa Head is one of the only places in the world where a visitor can get close to great albatrosses. The colony is tiny, with only 140 individuals, and the breeding effort is managed assiduously—"lovingly" would not be too strong a word. Royal albatross chicks are nest-bound for nine months. Providing meals for these chicks is so demanding that the parents take a year off before breeding again. Lyndon Perriman, the senior ranger, described to me some of the ingenious techniques used to maximize reproductive success. ..Previous Post Next Post