Effects of structural and functional connectivity and patch size on the abundance of seven Atlantic Forest bird species
Introduction
Connectivity and patch size are important parameters for the persistence of species in fragmented landscapes (Karr, 1982, Blake and Karr, 1987, Bierregaard and Stouffer, 1997, Stratford and Stouffer, 1999, Crooks et al., 2000). While connectivity is associated with migration rates, and thus with the (re)colonization probability and the rescue effect, patch size is mainly related to the probability of local extinction (Levins, 1970, Hanski and Gilpin, 1997).
Connectivity can be defined as the capacity of the landscape to facilitate biological fluxes (Taylor et al., 1993, Tischendorf and Fahrig, 2000). In structural terms, it can be evaluated by measuring landscape patterns, such as density and complexity of corridors (Beier and Noss, 1998), distance between patches, and inter-habitat matrix permeability (Metzger and Décamps, 1997, Gascon et al., 1999, Antongiovanni and Metzger, 2005). Functional connectivity is more complex. It depends not only on the landscape pattern, but also on the interactions between this pattern and the biological characteristics of the target species, such as their ability to move in areas of non-habitat (Greenberg, 1989, Sieving et al., 1996). For example, understory insectivorous birds, which are able to use more intensively deforested countryside, are less affected by fragmentation and have lower extinction risk (Sekercioglu et al., 2002). Interest in how species use different landscape elements to disperse is increasing (Tischendorf and Fahrig, 2000, Graham, 2001, Bélisle and Desrochers, 2002, Adriaensen et al., 2003) as it is linked with the probability of an individual finding patches of habitat that are spread across the landscape and, therefore, is related with species’ capacity to persist in such environments.
In the present study, we evaluated the abundance of seven Atlantic rainforest bird species in relation to patch size and connectivity, considering not only structural characteristics of the landscape but also movement behavior of species.
The Brazilian Atlantic rainforest has one of the highest levels of biodiversity and rates of endemism in the world, and is among the world’s top five threatened hotspots (Myers et al., 2000, Mittermeier et al., 1999). Despite strict environmental legislation, today less than 8% of the forest remains and deforestation persists (Dean, 1996, Fundação SOS Mata Atlântica/INPE, 2002). Due to habitat loss and the consequent fragmentation, populations are becoming isolated in small forest patches and many species, especially endemics (Ribon et al., 2003), are locally disappearing. For example, the Atlantic Forest has 188 endemic bird species (Pacheco and Bauer, 2000) and among them 102 are considered threatened (Pacheco and Bauer, 2000; IUCN, 2003).
There is a growing literature concerning the effects of deforestation and fragmentation on bird communities in this biome (Willis, 1979, Aleixo and Vielliard, 1995, Christiensen and Pitter, 1997, Anjos and Boçon, 1999, Brooks et al., 1999a, Maldonado-Coelho and Marini, 2000, Ribon et al., 2003), but few authors have considered aspects of connectivity. Since the response to fragmentation depends on the interaction between spatial characteristics of the landscape and the species’ behavior (Tischendorf and Fahrig, 2000), we analyzed connectivity in structural and functional terms. Structurally, we considered the presence or absence of connections (corridors) between small and larger patches in the landscape as well as the distance between patches. In functional terms, we measured the species’ capacity to use corridors and to cross open areas of the matrix. We considered only strict forest species because, by definition, they are more sensitive to forest fragmentation. An understanding of the mechanisms that maintain these species in fragmented landscapes will likely have applications to other less demanding species (Lambeck, 1997, Simberloff, 1998).
Section snippets
Study region
The study region is situated in the Plateau of Ibiúna, a Pre-Cambrian formation situated 40 km from the city of São Paulo (23°35′S–23°50′S; 46°45′W–47°15′W; Fig. 1). The elevation ranges from 870 to 1030 m, and the topography is dominated by small round hills (Ponçano et al., 1981). The weather is warm and humid, with mean monthly temperature varying between 11 and 27 °C. The annual precipitation is about 1300–1400 mm with seasonal variation, April to August being cooler and drier. The vegetation
Landscape structure
Mean nearest neighbor (MNN) values ranged from 30 to 90 m, with an average of 54 m (Table 1). Fragment size (log transformed) and isolation were uncorrelated (Pearson, r = −0.027, p = 0.930), which allowed the evaluation of the effect of these indices with bird abundances independently.
Sensitivity to landscape structure
The species showed varying patterns of abundance, indicating different degrees of sensitivity to fragmentation (Table 3). The comparison between forest and fragmented landscapes revealed that T. malachitacea and C.
Importance of area
The species in this study showed different degrees of sensitivity to habitat area and connectivity, supporting previous findings with birds and other taxonomic groups (Willis, 1979, Laurance, 1991, Newmark, 1991, Pearson, 1993, Andrén, 1994, Stouffer and Bierregaard, 1995, Jokimäki and Huhta, 1996). Patch size was particularly important to large canopy frugivorous species. This is not surprising as they probably have a large area requirement due to high energetic demand and to the spatial and
Acknowledgments
We thank Clinton Jenkins, Pedro Develey, Alexandre Martensen, and Pedro M. Pedro for revising a previous version of the manuscript. We are also grateful to Denis Saunders, Cagan Sekercioglu, and an anonymous reviewer for their detail analysis and efficiency throughout the review process. We appreciate the cooperation during all the steps of this study of members of the project “Biodiversity conservation in fragmented landscapes at the Atlantic Plateau of São Paulo”. We thank SABESP, which
References (78)
- et al.
The application of ‘least-cost’ modelling as a functional landscape model
Landscape and Urban Planning
(2003) - et al.
Influence of the matrix habitats on the occurrence of insectivorous bird species in Amazonian forest fragments
Biological Conservation
(2005) - et al.
Matrix habitat and species persistence in tropical forest remnants
Biological Conservation
(1999) - et al.
The structural connectivity threshold: an hypothesis in conservation biology at the landscape scale
Acta Œcologica
(1997) - et al.
Very large area requirements for frugivorous birds in monsoon rain forests of the Northern Territory, Australia
Biological Conservation
(1999) Consequences of forest fragmentation for the dynamics of birds populations: conceptual issues and the evidence
Biological Journal of the Linnean Society
(1991)Flagships, umbrellas, and keystones: is single-species management passé in the landscape era?
Conservation Biology
(1998)- et al.
Composição e dinâmica da avifauna da mata de Santa Genebra, Campinas, São Paulo, Brazil
Revista brasileira de Zoologia
(1995) Effects of habitat fragmentation on birds and mammals in landscapes with different proportions of suitable habitat: a review
Oikos
(1994)- et al.
Bird communities in natural forest patches in Southern Brazil
Wilson Bulletin
(1999)
Do corridors provide connectivity?
Conservation Biology
Gap-crossing decisions by forest birds: an empirical basis for parameterizing spatially-explicit, individual-based models
Landscape Ecology
Understory birds and dynamic habitat mosaics in Amazonian Rainforests
Breeding birds of isolated woodlots: area and habitat relationships
Ecology
La méthode des indices ponctuels d’abondance (I.P.A.) ou des relevés d’avifaune par “stations d’écoute”
Alauda
Atlantic forest extinctions
Nature
Deforestation and bird extinctions in the Atlantic Forest
Animal Conservation
Time lag between deforestation and bird extinction in tropical forest fragments
Conservation Biology
Heavy extinctions of forest avifauna in Singapore: lessons for conservation biodiversity in Southeast Asia
Conservation Biology
Species loss in a forest bird community near Lagoa Santa in Southeastern Brazil
Biological Conservation
Extinction and colonization of birds on habitat islands
Conservation Biology
A Ferro e Fogo – A história e a devastação da Mata Atlântica brasileira
Bird survival in an isolated Javan Woodland: island or mirror?
Conservation Biology
Rarity and body size: some cautionary remarks
Conservation Biology
Patterns of rarity in the birds of the Atlantic Forest of Brazil
Conservation Biology
Factors influencing movement patterns of Keel-Billed Toucans in a fragmented tropical landscape in Southern Mexico
Conservation Biology
Neophobia, aversion to open space, and ecological plasticity in song and swamp sparrows
Canadian Journal of Zoology
Metapopulation Biology: Ecology, Genetics, and Evolution
Predictors of species sensitivities to fragmentation
Biodiversity and Conservation
Avifauna da Floresta Atlântica, região de Salesópolis, Estado de São Paulo
Revista Brasileira de Biologia
The effects of landscape matrix and habitat structure on a bird community in northern Finland: a multi-scale approach
Ornis Fennica
Forest fragmentation and bird extinctions: San Antonio eighty years later
Conservation Biology
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