Uso de classes topográficas para descrever habitat de aves florestais amazônicas

Abstract

Bottomlands, slopes, and plateaus are landscape classes that aggregate distinct characteristics of soil and vegetation, which in turn are important for habitat selection by birds, making these classes potentially recognizable as habitats for Amazon bird species. To test whether species of terra firme forest birds select, are specialized in, or avoid any of these environments, we use the approach of the use of topographic classes versus its availability. Available environment corresponded to the frequency of each class in 600 ha of primary forest north of Manaus, Brazil, classified using height and percent of slope with GIS tools. Bottomlands were the lowest areas, and slopes and plateaus were defined by percent of slope above elevation limit for bottomlands. Bird data, from the TEAM Project database, were obtained in point count censuses in six 100-ha plots visited one to four times per year, for five years. These six plots comprised 36 points, each one, separated 200 m apart from each other, for a total of 216 sampled points. Slope was the most abundant class (47%), followed by plateaus (33%) and bottomlands (20%). In 160 species analyzed, 50 (31%) selected topographical classes, none of them were specialized and 16 (32%) avoided bottomland or plateau, but never slope. Our results showed that for a few species typical of forest streams, the topographic class “bottomland” represents preferred habitat. For other species, these topographical habitat associations represent novel hypotheses and should be investigated in greater detail. In general, previous natural history knowledge of these species suggests that the relationship between topographical category and specific habitat requirements are indirect, and the use of these classes to describe habitat should also consider relevant micro-habitat features for birds. Finally, our work represented an attempt to quantify the use of environment versus its availability to find out a more refined and functional habitat classification for birds within the terra firme forest, providing comparison base for further studies about habitat use by birds in the Amazon.