DAILY SCIENCE

Impoverished but still a treasure: the birds of an Amazonian city
Scientists delve into the living experiment playing out as a fantastically species-rich, ecologically-specialized rainforest bird community meets a radically different urban environment.
May 24, 2017

Though urban wildlife is getting more attention than ever, most of the focus is on North America and western Europe. Given urbanization’s pace all over the world, there’s a lot we’re missing. In Amazonia, the vast territory around the Amazon river basin, urban populations have swelled by 500 percent in the last half-century—yet until ornithologists Alexander Lees and Nárgila Moura spent an entire year counting birds in the northeast Brazilian city of Belém, no scientists had surveyed the avian life of an Amazonian city. “Amazonia is famed for its biodiversity,” says Lees, “yet for the millions of Amazonians living in urban areas, city birds are about the only wildlife they see.”

To Lees and Moura, who hail from, respectively, Manchester Metropolitan University and Cornell University, and who published their findings in the journal Urban Ecosystems, Amazonian city birds are of interest for several reasons: the intrinsic value of biodiversity, the utilitarian value of ecosystem services, and also the living experiment playing out as a fantastically species-rich, ecologically-specialized rainforest bird community meets a radically different urban environment. Belém, population 1.5 million, at the heart of an area that’s lost nearly 80 percent of its original forest cover, was an appropriate setting.

Several times each month between August 2014 and July 2015, the researchers recorded every bird they saw and heard along a three-mile transect through the city’s emblematic habitats: high- and low-rent housing, an urban park, a newly-gentrified stretch of riverfront, vacant lots. Altogether they documented 99 bird species, two-thirds of which were residents and the rest migrants. Most of the residents were species traditionally found in second-growth forests and along river edges. Five historically non-native species—feral pigeons, Jandaya parakeets, common waxbills, Campo troupials and house sparrows—accounted for a full one-fifth of all bird abundance. For a region possessing Earth’s most diverse bird fauna—with nearly 500 species once found locally—Belém’s birds were, in Lee and Moura’s words, “taxonomically depauperate.” Yet although “urban avian biodiversity in Belém was impoverished,” they write, “it should still be valued.”

Unlike in northern cities, where bird communities tend to be dominated by seed- and fruit-eaters, most of the birds in Belém belong to insect-eating groups. They have the potential to provide tremendous ecosystem services by controlling plant-damaging bugs and the insect vectors of human-infectious diseases such as Zika, malaria, and West Nile fever. Disease control by urban birds is “a research avenue that has largely been overlooked,” write Lees and Moura. So have the waste removal services performed by black vultures, the city’s dominant birds in terms of pure biomass.

Vultures also have a deep cultural significance. In pre-Columbian times they were venerated, appearing in origin myths and symbolizing rebirth and balance. People still regard them with affection. So too white-winged parakeets, who build huge roosts in the city center, and elegant great egrets in Belém’s main park. Birds like these offer a connection to nature, planting the seeds of an environmental ethic, says Lees. They “may provide one of the few connections that many Amazonian urban residents have to the natural world,” he and Moura write, “reinforcing the importance of Amazonian conservation far beyond the city’s boundaries.”

Source: Lees A and N Moura. “Taxonomic, phylogenetic and functional diversity of an urban Amazonian avifauna.” Urban Ecosystems. 2017.
Image: Alexander Lees / Manchester Metropolitan University

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