Despite having been deforested to the extent that only 10% of its original expanse remains, the Atlantic Forest is still literally in most Brazilians’ back yard. One in every seven people in Brazil lives in an area legally defined as part of this biome, which stretches along the ocean on the eastern edge of this country and cuts a swath through 17 states, from Piauí to Rio Grande do Sul. Scientists have just concluded the most complete, up-to-date survey of the diversity of birds that inhabit the remaining areas of this coastal garden, which is under pressure from the growth of cities.
Under the supervision of Luís Fábio Silveira, curator of the ornithology collection at the University of São Paulo Zoology Museum (MZ-USP), 29-year-old ornithologist Luciano Lima has produced a report, more than 500 pages long, in which he lists every known bird species in the biome, summarizes its main characteristics and places of occurrence and updates its conservation status (endangered or not). It took him five years to review the scientific literature and visit nearly every Brazilian state that contains portions of the Atlantic Forest. “The only states I didn’t visit were Sergipe and Mato Grosso do Sul,” says Lima, who lives in Resende, Rio de Janeiro State, near Itatiaia National Park, where he has been watching birds since the age of 13.
The sizeable numbers gleaned from the survey are revealing, and reinforce the biome’s importance to the world of birds. The Atlantic Forest is home to 891 bird species, which account for about 45% of all species found in Brazil. Amazonia has more species—about 1,300—but its area is four times larger, according to the geographic boundaries used by the Brazilian Institute of Geography and Statistics (IBGE). Approximately one-fourth of the bird species—213 in absolute numbers, or 24% of the total—are endemic to the Atlantic Forest. In the language of biology, endemic species are those found exclusively in a given type of plant formation, and nowhere else. Another 17 species are nearly endemic, that is, they occur primarily in the Atlantic Forest, and only marginally in other biomes.
A little more than 25% of all the species—233 in absolute numbers—are endangered, according to national and international lists of birds most likely to disappear from the planet. Not every endemic species is in danger, nor is every jeopardized species exclusive to the biome. Of the endangered species, however, 147 are endemic or nearly endemic to the Atlantic Forest. “That figure is really worrisome,” Lima says. According to the survey, the Atlantic Forest also has 1,035 bird subspecies, of which 351 are endemic. “This is the first time that data on the occurrence of bird subspecies in this biome have been presented in a study,” Silveira points out. In ornithology, the term “subspecies” refers to geographically isolated populations of a bird that are distinct from one another to some degree, but that have not been considered distinct enough to deserve species status. “This concept has been used indiscriminately in the Atlantic Forest, and many valid species of birds are ‘hidden’ beneath the name of a subspecies,” the MZ-USP researcher comments.
The data compiled and produced in Lima’s study differ from other works published in recent decades. Some relatively recent surveys even point to the existence of more than a thousand species of birds in the Atlantic Forest. The disparities were largely expected and unavoidable. “Lima used clearer criteria, based on the natural features of the biome and the biogeographic aspects of the species, to define exactly what constitutes an Atlantic Forest area and determine which birds actually inhabited those sections,” notes Silveira, thesis advisor to the young ornithologist, who completed his master’s degree this year with the study. “In the past, other studies used the legal definition of the Atlantic Forest, which also includes areas adjacent to the biome but that are actually parts of the Cerrado, the Caatinga or the Pampa.”
The overly liberal approach that prevailed until recently has inflated the number of species described as inhabitants of the Atlantic Forest. Birds were included that, strictly speaking, live in the vicinity of that type of plant formation, but in more precise terms they inhabit segments of other biomes, according to Silveira and Lima. To mitigate this problem, birds that live predominantly in a 100-kilometer (km) strip along the borders of other biomes—50 km inside the legal boundaries of the Atlantic Forest and 50 km outside of them—were not considered as belonging to that plant formation in the young ornithologist’s survey.
“Lima’s work puts the house in order and is becoming a benchmark in terms of Atlantic Forest birds,” says José Fernando Pacheco, a director of the Brazilian Ornithological Records Committee (CBRO), a forum associated with the Brazilian Ornithological Society that oversees the quality of data on the geographic distribution of birds in Brazil. “No one has ever devoted this much time to organizing the list of species in that biome. The adoption of any working criterion, of course, is always somewhat arbitrary, but the choices he has made are pertinent, and they make sense.”
More representative orders
More than half the Atlantic Forest species mapped belong to the order Passeriformes, the popular passerines, which make up 55% of the known types of birds on Earth. According to Lima’s study, there are 476 species of passerines in the biome. The birds in this order range from those that are commonplace in urban neighborhoods, such as sparrows, to little-known creatures that are endangered, for example, the Seven-colored Tanager (Tangara fastuosa). This colorful bird, a little over 10 centimeters in length, is found only in sections of the Atlantic Forest between the states of Rio Grande do Norte and Alagoas.
The second-most representative order is Apodiformes, with 53 species of hummingbirds and swifts. Ranking third are Charadriiformes, with 50 species of gulls and terns, followed by Accipitriformes (eagles and hawks, with 37 species), Piciformes (woodpeckers, toucans and aracaris, 36), Psittaciformes (macaws, parrots and parakeets, 31) and Gruiformes (gallinules, 25).
Even though it is the biome most widely studied by ornithologists, the Atlantic Forest still holds surprises. At times a new bird appears where it is least expected. This was true in the case of the first bird species endemic to the state of São Paulo, Formicivora paludicola, which occurs exclusively in marshes in the vicinity of Mogi das Cruzes. The bicudinho-do-brejo-paulista, or São Paulo Marsh Antwren, the popular name of the species, has just been described in a scientific paper. “Who would have thought that 50 kilometers from my workspace there would be a new, as yet unidentified, species?” comments Silveira, a co-author of the discovery (see text).
The variety of shapes and sizes of birds in the Atlantic Forest offers an impressive sight, as witnessed by the images accompanying this article. At right, a Saffron Toucanet (Pteroglossus bailloni), a member of the order Piciformes, which includes 36 species. A noisy and relatively abundant kin of the toucan, it is endemic to the Atlantic Forest and measures about 35 centimeters (cm) in length. It occurs from southern Bahia State to Rio Grande do Sul, including Paraguay and Argentina. Photo at bottom shows a pair of Three-toed Jacamars (Jacamaralcyon tridactyla), also endemic but in jeopardy of extinction. Historically, records show only sparse populations of these 18-cm-long birds, between southern Bahia and northern Paraná State. The photo on the following page shows an imposing Dusky-legged Guan (Penelope obscura), of the order Galliformes. Found throughout much of the Atlantic Forest, it can grow as large as 70 cm in length
Birds of the Atlantic Rainforest: species richness, composition and knowledge gaps (nº 2011/17032-7); Grant mechanism Master’s degree scholarship; Principal investigator Luís Fábio Silveira; Grant recipient Luciano Lima; Investment R$35,723.34 (FAPESP).