Bird species that occupy river edge in continuous forest tend to be less sensitive to forest fragmentation

Abstract

Along a distance gradient from a given river, two types of habitat can be recognized: natural river edge and forest interior, each one with its own vegetation characteristics and dynamics. In a continuous area of the Brazilian Atlantic Forest, we investigated (1) if bird communities are different between a riverbank of a small stream and an inland forest habitat; (2) if the species of the river edge habitat are the ones that persist in the most in forest fragments after deforestation of a continuous forest; (3) if the river edge habitat species are those that are less sensitive to forest fragmentation. It is expected that there are differences in the bird communities and the occupancy of some species between the two habitats. We allocated 16 sampling points in each of the habitats and sampled the birds by point counts with a short radius of 30 m. Results suggest that there is a significant difference between the composition of the bird communities of the river edge and forest interior habitats, although the species richness is similar. Six species were more likely to occupy the river edge and 14 species had a greater probability of occupancy in the forest interior. Species associated with the river edge habitat (15 species) tend not to be sensitive to forest fragmentation (12 species). In this study, we demonstrated that river-border species of continuous forest areas form a significant part of the bird communities that persist in small forest fragments, with intense edge effect. This shows that not all forest edge species are the result of the colonization from open areas. Congruently, species that occupy the most distant areas from the river vegetation in a continuous forest are those more sensitive to forest fragmentation. KEYWORDS: Atlantic Rainforest, bird sensitivity, forest interior, natural edge, probability of occupancy. tree species; also, it is common to have the fall of trees and consequently the creation of clearings that allow the occupation of bamboo species (Bianchini et al. 2001, Anjos et al. 2007). This lowland riparian environment constitutes a transition between the river and the associated upland forest, marking a natural border or ecotone boundary. A forest ecotone is a consequence of the meeting of distinct natural plant communities, which, in turn, influences the diversity of wild animals across the landscape, dependent on distance from a rivers' edge and the characteristic transition in topography, plant community, hydrological regimes, and soil types (Naiman et al. 1993, Shirley 2005). Considering several taxonomic groups, some studies suggest greater species richness in riparian environments compared to distinct forest (Naiman et al. 1993), others found greater richness in non-riparian environments (McGaragal & McComb 1992, Peres 1997) and some found no difference between these two habitat types (Gomez & Anthony 1998, Rykken et al. 2007). On birds, several studies indicated the great importance of the riparian environment (natural river edges) as a uniquely sustaining habitat with relat...

An ornithological inventory in a reforested woodlot in western Paraná state, southern Brazil

“…Prior to the 21 st century, the avifauna of western and northwestern Paraná (a region which encompasses distinct biomes and types of soil), and especially areas surrounding the Paraná river, was characterized by Sztolcman (1926), Naumburg (1937Naumburg ( , 1939, Pinto & Camargo (1956), Scherer-Neto (1983), Anjos & Seger (1988) and Straube & Bornschein (1989, 1995. In the current century, studies have focused on the PNI (Straube & Urben-Filho, 2004;Straube et al, 2004) and more specific reports have been produced (Bencke et al, 2008;Cândido-Jr. et al, 2008;Von Matter et al, 2010;Girardi & Carrano, 2014;Lindsey et al, 2019).…”

Composition, richness and nestedness of gallery forest bird assemblages in an Amazonian savanna landscape: lessons for conservation

“…Thus, their species assemblages are expected to be dominated by generalist species with good dispersal ability (two functional traits). This hypothesis has received support from studies on riparian forest corridors that were created due to human interventions on the landscapes ( e.g ., Metzger, Bernacci & Goldenberg, 1997 ; Lees & Peres, 2008 ; Seaman & Schulze, 2010 ; de Oliveira Ramos & dos Anjos, 2014 ; Lindsey, Bochio & Anjos, 2019 ), but it has never been formally tested in natural forest corridors, such as gallery forests. If Forman’s hypothesis is correct and the distributions of gallery forest species across savanna landscapes are indeed determined by a combination of habitat attributes and inter-specific differences in habitat specificity and dispersal ability, then local assemblages formed by such species are expected to show a nested distribution pattern, in which less diverse assemblages are a nested subset of more diverse assemblages living close to continuous forests ( Ulrich, Almeida-Neto & Gotelli, 2009 ; Ulrich & Almeida-Neto, 2012 ).…”