Birds in Anthropogenic Landscapes: The Responses of Ecological Groups to Forest Loss in the Brazilian Atlantic Forest

RESEARCH ARTICLE Birds in Anthropogenic Landscapes: The Responses of Ecological Groups to Forest Loss in the Brazilian Atlantic Forest José Carlos Morante-Filho1*, Deborah Faria1☯, Eduardo Mariano-Neto2☯, Jonathan Rhodes3,4 1 Applied Conservation Ecology Lab, Programa de Pós-graduação Ecologia e Conservação da Biodiversidade, Universidade Estadual de Santa Cruz, Rodovia Ilhéus-Itabuna, km16 /Salobrinho, Ilhéus, Bahia, Brazil, 2 Instituto de Biologia, Universidade Federal da Bahia, R. Barão Jeremoabo, Ondina, Salvador, Bahia, Brazil, 3 School of Geography, Planning and Environmental Management, The University of Queensland, St Lucia, Brisbane, Queensland, Australia, 4 ARC Centre of Excellence for Environmental Decisions, The University of Queensland, Brisbane, Queensland, Australia ☯ These authors contributed equally to this work. * OPEN ACCESS Citation: Morante-Filho JC, Faria D, Mariano-Neto E, Rhodes J (2015) Birds in Anthropogenic Landscapes: The Responses of Ecological Groups to Forest Loss in the Brazilian Atlantic Forest. PLoS ONE 10(6): e0128923. doi:10.1371/journal.pone.0128923 Academic Editor: Philip Gibbons, The Australian National University, AUSTRALIA Received: November 19, 2014 Accepted: May 3, 2015 Published: June 17, 2015 Copyright: © 2015 Morante-Filho et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This study was possible due to the collaborative work of the REDE SISBIOTA team, with the financial support by Conselho Nacional de Desenvolvimento Científico e Técnologico (CNPq; grant number 69014416) and Universidade Estadual de Santa Cruz (grant number 002011001171). JCMF thanks the Fundação de Amparo à Pesquisa do Estado da Bahia for the fellowship (FAPESB, grant number 462/2012). DF received a grant from CNPq (number 307221/2012-1). This study was also supported by funding from the Australian Research Abstract Habitat loss is the dominant threat to biodiversity and ecosystem functioning in terrestrial environments. In this study, we used an a priori classification of bird species based on their dependence on native forest habitats (forest-specialist and habitat generalists) and specific food resources (frugivores and insectivores) to evaluate their responses to forest cover reduction in landscapes in the Brazilian Atlantic Forest. From the patch-landscapes approach, we delimited 40 forest sites, and quantified the percentage of native forest within a 2 km radius around the center of each site (from 6 - 85%). At each site, we sampled birds using the point-count method. We used a null model, a generalized linear model and a four-parameter logistic model to evaluate the relationship between richness and abundance of the bird groups and the native forest amount. A piecewise model was then used to determine the threshold value for bird groups that showed nonlinear responses. The richness and abundance of the bird community as a whole were not affected by changes in forest cover in this region. However, a decrease in forest cover had a negative effect on diversity of forest-specialist, frugivorous and insectivorous birds, and a positive effect on generalist birds. The species richness and abundance of all ecological groups were nonlinearly related to forest reduction and showed similar threshold values, i.e., there were abrupt changes in individuals and species numbers when forest amount was less than approximately 50%. Forest sites within landscapes with forest cover that was less than 50% contained a different bird species composition than more extensively forested sites and had fewer forest-specialist species and higher beta-diversity. Our study demonstrated the pervasive effect of forest reduction on bird communities in one of the most important hotspots for bird conservation and shows that many vulnerable species require extensive forest cover to persist. PLOS ONE | DOI:10.1371/journal.pone.0128923 June 17, 2015 1 / 18 Identifying Bird Community Responses to Forest Reduction Council Centre of Excellence for Environmental Decisions. Competing Interests: The authors have declared that no competing interests exist. Introduction Habitat loss and fragmentation are the major drivers of current rates of biodiversity decline [1]. Although habitat loss generally increases the likelihood of stochastic extinction and declines in population sizes at local and landscape scales, fragmentation effects, i.e., the transformation of the original habitat into a number of isolated fragments in a matrix of habitats that is unlike the original [2], can have positive and/or negative effects depending on species characteristics [1], [3]. Further, although habitat loss and fragmentation are different processes and have different adverse effects on biodiversity, population persistence in anthropogenic landscapes is a result of the interaction of both processes [4], [5]. Ecological studies have shown that the relationship between habitat loss at the landscape scale and extinction of species can be nonlinear [6–8]. The extinction threshold hypothesis states that many species require a given amount of suitable habitat to persist in the landscape. Fragmentation has its most pronounced effects at values that are below this threshold and can lead to abrupt decreases in species population size [4], [9], [10]. Extinction thresholds are proposed to occur when less than 30% of habitat remains, due to a decrease in mean patch size and to an exponential increase in the distance between patches [4], [8]. Attempts to uncover the relative importance of fragmentation and habitat amount have proved a difficult task particularly because there is generally high correlation of most fragmentation metrics to habitat loss, but empirical studies have identified habitat amount as the prevailing driver of species loss [8], [11]. The concept of extinction thresholds was primarily derived from simulations of population responses to habitat loss in neutral landscapes, and current empirical studies have focused more on populations than on communities [4], [12]. The existence of thresholds in communities in response to habitat loss has not always been supported by the published results of empirical studies and is still controversial [12–14]. Threshold values for remaining habitat that range from 5% to 90% have been documented [12], [15], [16]. Such variation might be due to species characteristics, the different measures used to test thresholds (e.g., habitat amount, patch isolation and patch size), the duration and intensity of changes in the landscape, the nature of the matrix and the spatial scale of the studies [9], [14], [17]. Thresholds can also vary among study regions for the same speci (...truncated)