Spatial and temporal changes in bird assemblages in forest fragments in an eastern Amazonian savannah

Abstract

We investigated the effects of forest fragmentation on bird assemblages in an Amazonian savannah landscape with forest fragments that have been isolated for more than 100 years. The study was conducted in areas surrounding the village of Alter do Chão (2°31'S, 55°00'W), Santarém, Brazil. Bird surveys and measurements of tree density were undertaken in 25 areas, with 19 plots in forest fragments of different sizes and six in an area of continuous forest. Data on forest-fragment size, perimeter, and isolation were obtained from a georeferenced satellite image. Variation in number of bird species recorded per plot was not related to vegetation structure (tree density). The number of bird species recorded per plot increased significantly only with fragment area, but was not influenced by fragment shape or degree of isolation, even when considering species from the savannah matrix in the analysis. Fragments had fewer rare species. Multivariate ordination analyses (multiple dimensional scaling, [MDS]) indicated that bird species composition changed along a gradient from small to large forest fragments and continuous-forest areas. In the Amazonian savannah landscapes of Alter do Chão, the organization and composition of bird assemblages in forest fragments are affected by local long-term forest-fragmentation processes. Differences in the number of bird species recorded per plot and assemblage composition between forest fragments and continuous forest were not influenced by forest structure, suggesting that the observed patterns in species composition result from the effects of fragmentation per se rather than from preexisting differences in vegetation structure between sites. Nevertheless, despite their long history of isolation, the forest fragments still preserve a large proportion (on average 80%) of the avifauna found in continuous-forest areas. The fragments at Alter do Chão are surrounded by natural (rather than planted) grassland, with many trees in the savannah matrix and the landscape has vast areas covered by forest, which may have helped to ameliorate the influences of forest fragmentation.

Response of Understory Bird Feeding Groups to Deforestation Gradient in a Tropical Rainforest of Cameroon

“…The conversion of natural habitats to agricultural areas involves the use of heavy machinery, felling, and dragging of trees over long distances. As a result, the forest is open and fragmented, its structure and composition are heavily damaged, and this may lead to local extinction and reduction of biological diversity of many taxa (Cintra, Magnusson, & Albernaz, 2013). Habitat loss and fragmentation are among the greatest threats to biodiversity (Gibson et al., 2011).…”

The Program for Biodiversity Research in Brazil: The role of regional networks for biodiversity knowledge, dissemination, and conservation

“…Researchers have also undertaken studies of environmental impacts of extensive infrastructure programs (Bobrowiec & Tavares 2017), fire ecology (e.g. Fadini & Lima 2012), island biogeography and metapopulation dynamics (Carvalho et al 2008, Cintra et al 2013, methods in ecology (Norris et al 2014, Madalozzo et al 2017, Fontana et al 2018, population ecology (Brigatti et al 2016, Ferreira et al 2016, population genetics and phylogeography (Collevatti et al 2014, Melo et al 2016, Vitorino et al 2016 PPBio has produced several books about the ecology of Brazilian ecosystems and identification guides for specific groups of funga, fauna, and flora (e.g. Costa et al 2011, Baccaro et al 2015, Iop et al 2016, Peixoto et al 2016.…”

Avifauna of two Forest Fragments near the City of Altamira, Pará, Brazil

“…According to Neto et al [3], the reduction of vegetation cover to small fragments, causes negative consequences for the bird, thus causing a decline in the number of more specialized species, favoring the generalists, which became predominant, and such a disruption of forest composition can directly influence the distribution of conditions and resources in an unfavorable way for the group. Already for Cintra et al [4]. The differences in the number of bird species recorded in forest fragments and continuous forest of the eastern Amazonia were not influenced by forest structure, suggesting that the observed patterns in species composition result from the effects of fragmentation per se rather than from preexisting differences in vegetation structure between sites.…”