A summer and winter's tale: factors influencing avian community composition and species abundances in lowland subtropical floodplain forests in central eastern Australia

The ecology of avian community assembly in subtropical climate areas with seasonal and year-to-year variability is complex and poorly understood. To test for variation in year year and seasonal (summer winter) avian community composition and species abundances, we established 10 transects (200 m long) and sampled twice yearly for 7 years. To differentiate year-year and seasonal (summer-winter) patterns from the potential disturbance effects caused by human activities associated with music festivals (events), we monitored community composition and species abundances on sites close to disturbance areas (impact) and sites distant from disturbances (control). Impacts from large scale music events included loud noise, and thousands of vehicle and people movements on a daily basis. Raw count, abundance-weighted, and feeding guild data were analysed using multivariate and univariate methods. Seasonal (summer-winter) patterns of food resource availability in dominant forest trees (fruit and nectar resources) were identified. We found strong signals for the influence of seasonality and seasonal resource availability on community composition and feeding guild representation (nectivores and frugivores). We detected somewhat weaker effects for location relative to disturbance (control vs impact) and weak effects for sample timing associated with disturbance from the events. Avian community composition showed high similarity between control and impact sites, was dynamic in space and time (year to year) and showed strong local and regional trends in response to seasonality. Avian species abundances were greater in less disturbed (control) forest habitats, highlighting the fundamental value of conservation reserves in protecting higher quality avian habitats.