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Ecology

The land of the birds

Now there are eight species of birds that only between the Xingu and Tapajós rivers

Being home to two species of birds that are not found in any other place on the planet by itself characterizes a region as a center of endemism. The area between the Xingu and Tapajós rivers, in the Amazon basin, has eight of these exclusive species, and one of them was discovered recently by a team of researchers from Pará. It is a woodcreeper, called Carajás woodcreeper (Xiphocolaptes carajaensis) in reference to the place where it was found: the Carajás mountain range, in Pará. It measures 30 centimeters from the end of its tail to the tip of its beak, it weighs some 110 grams, and has a peculiar plumage: the body is covered with greenish -brown feathers, with chestnut colored wings and tail.

The woodcreepers are related to the family of the joão-de-barro , a kind of ovenbird, but they climb up tree trunks like a woodpecker, using their tail as a support. In a comparison with the other species of woodcreepers of the Xiphocolaptes genus, the white stripes that it has on the head are broader, while the wings, the tail and the beak are smaller. They sing early in the morning and at the end of the day – a song that is made up of a series of whistles that starts on a high note, and is easier to be heard at the time of reproduction, between September and January.

These particularities result from a process called speciation – when a population from the same species is split up into two, each one of which differentiates itself and originates a new species. The separation is usually caused by geographical barriers – such as rivers, in the case of the new species of woodcreeper. The Carajás woodcreeper must have originated between 2 and 3 million years ago, when the Pliocene age gave way to the Pleistocene period, when the current courses of the rivers of the Amazon basin were formed.

It used to be thought that the differentiation of the species of the Amazonian birds was recent – it was said to have happened in the last few thousands of years. However, with the appearance of molecular techniques, today’s estimates indicate that differentiation between sister species, those that descended from the same ancestor, took place between 1 and 3 million years ago. “This means that the current species are much older than was previously thought”, says one of the authors of the discovery, José Maria Cardoso da Silva, a professor on leave from the Federal University of Pernambuco (UFPE), who is coordinating Conservation International do Brasil’s program for the Amazon.

Finding a new species of bird, though, is not all common. On average, three new ones are identified a year – the lowest rate amongst all groups of organisms. Like other vertebrates, birds are almost all known, in Brazil, there are 1,680 identified species, and some 9,000 in the world. Of woodcreepers alone, some 50 species have already been described, of which 39 live in Brazilian territory.The new species was observed for the first time in July 1985, during an expedition to a forest area inside the mining concession of Vale do Rio Doce, in the Carajás mountains.

On that trip, Silva discovered the bird and then lost it from sight. Only three days later, when he was getting ready to go back to Belém, did he manage to catch one specimen, using a mist net, made of fine nylon to confuse the birds. “Woodcreepers move quickly and are difficult to follow for long”, the ornithologist explains. He described the new species in an article published in September in the British scientific magazine, the Bulletin of the British Ornithologists’ Club, along with another two ornithologists: David Oren, currently the scientific director of The Nature Conservancy do Brasil, and Fernando Costa Novaes, a retired researcher from the Emílio Goeldi Museum, in Belém.

Silva was only sure that he was dealing with a new species six months later, when comparing the specimen he had caught with the bird collection at the Emílio Goeldi. But to describe a new species, more specimens needed to be obtained. “I returned to the jungle and had to get another one”, he says. Later on, he found other specimens in the National Museum of Natural History, in Washington (USA) and in the Zoology Museum of the University of São Paulo (USP) – they were recorded as the closest species to them, the strong-billed woodcreeper (Xiphocolaptes promeropirhynchus), which is found on the other side of the Xingu. With five specimens, he was finally able to make the necessary comparisons and to write the work on the new bird.

Although they build their nests in the hollow parts of trees, hiding themselves away from anyone wanting to see them or to photograph them, woodcreepers are incapable of excavating – they take advantage of holes that have already been opened. Inside them, they lay their eggs on a sort of mattress made of bits of bark and dry leaves. According to Silva, in spite of there being little change in their coloring – they are usually brown – woodcreepers vary a lot in the shape and size of their beaks: there are species with a small and straight beak, others with one that is long and curved, like the black-billed scythebill (Campylorhamphus falcularius).

In the article on the new bird, the researchers warn of the need for conservation of the species and of its habitat. “Woodcreepers are very sensitive to alterations in the environment, and they are among the first groups of birds to disappear when the forest is broken up or when timber is exploited commercially”, says Silva. It is a concrete threat: some 25% of the 394,515 square kilometers of the Xingu Endemism Center have now been cleared.

It is there that another eight species or subspecies of endemic birds live: the dark-winged trumpeter (Psophia viridis interjecta), Neumann´s pearly conure (Pyrrhura perlata anerythra), a bare-eye (Phlegopsis confinis), the white-backed fire-eye (Pyriglena leuconota interposita), the white bellbird (Procnias alba wallacei), the chestnut-belted gnateater (Conopophaga aurita pallida) and two other woodcreepers, theHylexetastes brigidai and a new species that has yet to be described, Dendrocincla sp .

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