Habitat heterogeneity drives bird species richness, nestedness and habitat selection by individual species in fluvial wetlands of the Paraná River, Argentina

Abstract

We assessed the relationship between habitat heterogeneity and bird species richness and composition within wetlands of the floodplain of the Middle Paraná River, Argentina. Given the high habitat heterogeneity in these wetland systems, we sought to determine whether (i) there was a positive relationship between bird species richness and habitat heterogeneity; (ii) whether bird species richness was associated with certain types of individual habitat types; (iii) whether there was a pattern of species nestedness and turnover between sites as a function of habitat heterogeneity and composition, respectively; and (iv) whether individual species exhibited associations with habitat heterogeneity. Point counts were used to survey birds at 60 sites. We estimated the area of eight habitat types found within a 200-m radius from the centre of each site and calculated number and Pielou's evenness of habitat types. These indices, together with area proportion of each habitat type, were used as explanatory factors of bird species richness in linear regression models. Habitat heterogeneity per se rather than area of individual habitat types was a more important predictor of species richness in these fluvial wetlands. Sites with more habitat types supported more bird species. Results showed that individual bird species were associated with different habitat types and, therefore, sites that contained more habitat types contained more species. Number of habitat types accounted for species nestedness between sites whereas composition of habitat types accounted for species turnover between sites. Results suggest that selection of heterogeneous sites by individual species could help explain the positive heterogeneity-species richness relationship. Our findings highlight the importance of habitat heterogeneity per se resulting from flood disturbances in maintaining bird richness in fluvial systems.

Habitat‐mediated influence of water‐level fluctuations on waterbird occurrence in floodplain wetlands of the Parana River, Argentina

“…Different aspects of life histories and ecological attributes among species may provide information with which to predict responses of waterbirds to hydrological fluctuations (Okes, Hockey, & Cumming, ). Because waterbird species use different habitats within floodplains (Colwell & Taft, ; Lorenzón, Beltzer, Olguin, & Ronchi‐Virgolini, ) and because these habitats are affected in different ways by water‐level fluctuations, habitat requirements could be especially important for predicting the responses of waterbird species to hydrological fluctuations in these systems. Changes in the availability of resources as a result of hydrological fluctuations may be related to actual changes in food abundance because prey of waterbirds are also affected by fluvial dynamics (Royan, Hannah, Reynolds, Noble, & Sadler, ).…”

Temporal variation of regional bird assemblages in highly dynamic fluvial wetlands: seasonality and influence of water level and habitat availability

“…We did not find a correlation between species richness, water level and number of habitats. Thus, although habitat heterogeneity accounts for the spatial variation of species richness at the local scale (Lorenzón et al, 2016), this variable did not explain temporal variation in the regional richness of the fluvial system.…”

“…We sampled birds over a wide area with substantial environmental heterogeneity in each survey by sampling 60 point counts over approximately 450 km along the fluvial system. The high environmental heterogeneity included in each survey allowed us to sample a high number of spatial niches of the fluvial wetlands, which have been shown to be good predictors of the bird composition of the system (Lorenzón, Beltzer, Olguin, & Ronchi-Virgolini, 2016). The relatively large sample size reduced effects of sampling error on estimates of temporal beta diversity (i.e.…”

“…Birds are among the most conspicuous and abundant vertebrates of fluvial wetlands, characteristics that have made them a key group for understanding the process that are occurring within fluvial ecosystems and further to know where and how to put conservation efforts for these systems (Davis, 1994). Different species use the mosaic of environments of fluvial wetlands in different ways, adjusting their use in accordance with the changing dynamics of these systems (Kingsford, Jenkins, & Porter, 2004;Lorenzón, Beltzer, Olguin, & Ronchi-Virgolini, 2016). Despite their importance, studies about the relationships between bird assemblages and hydrological regimes of fluvial wetlands are still very scarce (e.g.…”

Wetland Characteristics and Wintering Passerellidae Occupancy on Agricultural Conservation Easement Program Wetlands in West Virginia

“…Similarly, wetlands that occur within complexes of different habitat types could contribute to the species that occupy the wetland sites. Breeding season studies assessing the impact of habitat heterogeneity found that different habitat types near wetland sites increased species richness (Lorenzon et al 2016), and this concept can also be applied to winter habitat use due to differing species-specific habitat associations.…”