Wetland dependency drives temporal turnover of bird species between high‐ and low‐water years in floodplain wetlands of the Paraná River

Abstract

Temporal turnover of species between predominantly aquatic and terrestrial phases of floodplains, a process that helps maintain the high bird diversity of river–floodplain systems, could be driven by dependency of species on wetlands. To assess this, we compared the bird assemblages of river–floodplain systems at 60 sites along the Paraná River during the nonbreeding seasons of 2011, when water levels were predominantly high (high‐water year), and 2012, when levels were predominantly much lower (low‐water year). Birds were sampled by point counts repeated four times during each year at each site. We tested whether temporal patterns differed between wetland‐dependent and nonwetland‐dependent birds because these groups show positive and negative relationships, respectively, with water‐level increases. Species composition varied between years. Ten of the 14 species associated with high water levels in 2011 were waterbirds, and 11 of the 14 species associated with lower water levels (2012) were nonwetland species. Species richness and abundance per site of waterbirds and abundance of wetland species were higher during the high‐water year than in the low‐water year. Species richness, abundance, and diversity per site of nonwetland birds were, on the other hand, higher during the low‐water year than in the high‐water year. Species turnover between predominantly high‐ and low‐water periods did not respond to shorter term water‐level fluctuations within each year. In conclusion, our results show that degree of wetland dependence drives bird species turnover as a function of water‐level fluctuations, showing the importance of hydrological variability for bird conservation in river–floodplain systems.

Bird dependence on wetlands determines functional responses to flood pulse in the Brazilian Pantanal

“…On the other hand, non-wetland birds predominated during ebb and drought, and were less abundant in flooding and full flood, corroborating our initial hypothesis. This agrees with the study of Lorenzón et al (2020), which also found higher abundance values for non-wetland birds during the lowwater period.…”

“…The degree of wetland dependence influenced the birds' response to the flood pulse in the Pantanal wetland. Species richness and abundance of individuals were higher for non-wetland birds than waterbirds and wetland birds, a result similar to that found in another South American river system (Lorenzón et al 2020). Such results can be attributed to the fact that most neotropical bird species, in general, live in forest or non-forest habitats (~88%), while a much smaller number (~12%) is directly associated with wetlands or aquatic habitats (Stotz et al 1996).…”

“…This result indicates that evaluating only the general species assemblage can mask important wetland-dependent responses of birds, as observed for forest-dependent birds (Matuoka et al 2020). This is so because birds in wetlands can be affected differently by disturbances due to their response to water level (Lorenzón et al 2020) throughout the seasons (Che et al 2019), as well as regarding the wetland type, degree of environmental conservation (Almeida et al 2020) and degree of connectivity of the water-bodies (Almeida et al 2016). Still, biotic factors such as functional characteristics can be considered the main determinants of ecosystem processes, regardless of the hydrological regime (Setubal et al 2020).…”

“…For the classification of birds groups, we followed Lorenzón et al (2020), who categorize birds into three groups according to the degree of wetland dependence: (1) waterbirds, birds that have morphological adaptations to live in aquatic environments; (2) wetland birds, species that depend on resources or habitats in wet systems for food or reproduction; and (3) non-wetland birds, for those associated with terrestrial habitats, such as forest and savanna environments, or generalist habits, but that are not wetland-dependent. For the taxonomic classification of bird species, we followed Piacentini et al…”

“…Wetland ecosystems such as Pantanal, in turn, provide ideal places for breeding, resting, feeding, and are an important stopover and route for migratory bird species (Somenzari et al 2018;Jahn et al 2020). In addition, wetland dependence can drive the turnover of bird species depending on the water level in floodplains (Lorenzón et al 2020). However, the ecosystem functions of birds in wetlands are often overlooked due to the lack of essential information on their interactions in these environments (Green and Elmberg 2013).…”