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

Abstract

Hydrological regimes in floodplains are essential to support biodiversity that depend on wetlands, and understanding how these organisms are associated to this ecosystem could be useful, as they can act as important agents for the maintenance of diversity and natural processes. We aimed to assess the bird functional responses to the Pantanal flood pulse, considering the hydrological periods and three bird groups with different degrees of wetlands dependence. For this, bird survey was conducted in the Paraguay River floodplain system, covering the hydrological periods of the 2017–2018 cycle. We considered species richness, abundance, four functional diversity measures, and functional trait composition as ecological responses. Species richness was higher for bird group with lower degree of wetland dependence, mainly in drought and ebb periods. On the other hand, we found that the higher the degree of wetland dependence by birds, the higher the differences in the functional-trait values over periods. Abundance was affected by the variation of the hydrological periods for all bird groups. Bird groups had distinct niches, and functional traits associated with waterbirds were dominant in all periods. We found that degree of wetland dependence is driving the response of birds to changes in hydrological periods. Measuring only species richness may not reflect the inherent characteristics of this ecosystem. Bird groups such as waterbirds and wetland birds showed greater functional diversity throughout the hydrological periods, evidencing the importance of the flood pulse regime for species that are highly dependent on these environments and that perform many ecological services.