Stability and predictability of bird assemblages in an arid riparian woodland during contrasting periods of resource availability

Abstract

AbstractRiver red gum woodlands associated with ephemeral river channels in arid Australia are recognised as important habitat for a suite of bird species, due to their distinctive structure, large canopies and abundant tree hollows. We tested the proposition that river red gum woodlands harbour a distinctive bird assemblage that is relatively stable through time. We examined patterns of bird composition between habitats (riparian woodland versus neighbouring habitat) over multiple years (from 2016 to 2018) and locations (three catchments), and we assessed these patterns in the context of variable food resource availability. Assemblages in river red gum woodlands differed from those of adjacent vegetation, despite strong temporal variability caused by arrival of nomadic species in both habitat types following above‐average rainfall. Species richness was reduced in the drier periods, yet bird assemblages in river red gum woodlands retained their distinctiveness from adjacent habitat. Flowering and fruiting of shrubs and trees were largely stimulated by rainfall; in contrast, invertebrate abundance was driven more by temperature and was higher in river red gum woodlands. Our data did not imply that river red gum woodland acted as a refuge in drier times for species from neighbouring habitat. Our study supports the hypothesis that arid bird community composition is influenced more by habitat than by temporal resource variability.