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Spatial Distribution of Formicivora littoralis (Thamnophilidae) in a coastal fragment of Rio de Janeiro state, southeastern Brazil. Navegantes, A. Q. ¹, Bruno, S. F. ¹, Vecchi, M. B. ², Bessa, R. A. C. ¹ and Martins, A. R. 3.
Spatial Distribution of Formicivora littoralis (Thamnophilidae) in a coastal fragment of Rio de Janeiro state, southeastern Brazil.
Navegantes, A. Q. ¹, Bruno, S. F. ¹, Vecchi, M. B. ², Bessa, R. A. C. ¹ and Martins, A. R.3
1 Departamento de Medicina de Animais Selvagens, Universidade Federal Fluminense (UFF), Niterói, RJ, Brazil; 2 - DEcol, Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ, Brazil. 3 – Museu Nacional do Rio de Janeiro/UFRJ, Departamento de Vertebrados, Setor de Herpetologia. Email: email@example.com
INTRODUCTION The RestingaAntwren, Formicivoralittoralis Gonzaga and Pacheco, 1990 (Fig. 1) is considered the only endemic bird of restinga(sandy coastal plain vegetation) habitats, being critically endangered (IUCN, 2010). Its’ distribution is restricted to Região dos Lagos, Rio de Janeiro state, being reported for the municipalities of Saquarema, Araruama, Iguaba Grande, Arraial do Cabo, São Pedro D’ Aldeia, Cabo Frio and more recently in Armação dos Búzios (VECCHI & ALVES 2008; MATTOS et al. 2009). This species is considered extremely sensitive to habitat loss and fragmentation, which constitute the main threats to its remaining populations. The aim of this study was to identify key environmental variables, with emphasis on characteristics of vegetation, related habitat use by Formicivoralittoralis, as well as defining its effective area of occupancy in the fragment studied.
From 132 surveys made in the transects, we obtained 38 records of F. littoralis(Table 1). Considering these records, 63% were associated to restinga areas near Araruama’s lagoon, checking its higher abundance in initials segments near the beach, with few records in interior portions of dry forest (savanaestépica) (Fig 3).
Table 1 - Number of records of Formicivora littoralis for each plot of 50 m on each track sampled.
Figure 1 – Male (left) and female (right) of Formicivora littoralis. (photo Sávio Bruno)
MATERIAL AND METHODS
This study was conducted in the Núcleo Experimental de Iguaba Grande (NEIG), situated on the central coast of Rio de Janeiro.
We sampled six transects of 300 m each (Fig. 2), perpendicularly Araruama’s lagoon margins between December 2008 and September 2009 in order to estimate the distribution and habitat characterization of F. littoralis.
In order to map the species distribution, we used three types of registers: spontaneous registers, occasional registers and playback use. In order to characterize the habitat, measurements of eight vegetation variables were made: depth of litter, number of layers of vegetation, canopy height, vegetation density, canopy cover, presence of cacti and bromeliads and the distance from the lagoon (beach).
The eight measured enviromental variables were reduced by Principal Component Analysis (PCA). After that, the relationship between the three main axes of the PCA and the abundance of F. littoralis were tested through multiple regression.
Figure 3 – Total occurrence records of Formicivora littoralis in the Núcleo Experimental de Iguaba Grande (NEIG), Rio de Janeiro, Brazil.
Within the environmental variables analyzed, the most associated with the abundance of F. littoralis were the number of layers of vegetation, density of vegetation, distance from the lagoon and the presence of cacti.
Considering these variables, only the distance from the lagoon was inversely related to the abundance of the species.
These results confirm that F. littoralis tend to select dense shruby areas with cacti occurrence and near water. Although F. littoralis avoid disturbed areas, the species was sometimes recorded in patches of exotic vegetation. However, these records were restricted to zones of contact with native vegetation, and shrubs of similar size and density of the restinga.
Figure 2 – Núcleo Experimental de Iguaba Grande (NEIG), Rio de Janeiro, indicating the approximate location of the six transects (white lines) used for the systematic sampling of Formicivora littoralis.