Data from: Functional redundancy in bird community decreases with riparian forest width reduction

1. Riparian ecosystems are suffering anthropogenic threats that reduce
biodiversity and undermine ecosystem services. However, there is a great
deal of uncertainty about the way species composition of assemblages is
related to ecosystem function, especially in a landscape fragmentation
context. 2. Here we assess the impact of habitat loss and disturbance on
Functional Diversity (FD) components Functional Redundancy (FRed),
Functional Evenness (FEve) and Functional Richness (FRic) of riparian
forest bird assemblages to evaluate (1) how FD components respond to
riparian forest width reduction and vegetation disturbance; (2) the
existence of thresholds within these relationships; (3) which of the main
birds diet guild (frugivores, insectivores and omnivores) respond to such
thresholds. We predict that FD components will be affected negatively and
non-linearly by riparian changes. However, guilds could have different
responses due to differences of species sensitivity to fragmentation and
disturbance. We expect to find thresholds in FD responses, because
fragmentation and disturbance drive loss of specific FD components. 3. Our
results show that FRed and FEve were linearly affected by width and
disturbance of riparian habitats, respectively. FRed was significantly
lower in riparian forests assemblages below 400 m wide and FEve was
significantly higher above 60% disturbance. These responses of FD were
also followed to the decline in insectivores and frugivores richness in
riparian forests most affected by these changes. 4. Consequently, our
study suggests communities do not tolerate reduction in riparian forest
width or disturbance intensification without negative impact on FD, and
this becomes more critical for riparian area less than 400 m wide or with
more than 60% disturbance. This minimum riparian width required to
maintain FRed is greater than the minimum width required for riparian
forests by Brazilian law. Thus, is important to consider mechanisms to
expand riparian habitats and reduce the disturbance intensity in riparian
forests so that riparian bird community FD may be effectively conserved.