Extensive flooding the in the Lower Murrumbidgee catchment in October 2010 resulted in the establishment of colonial waterbird breeding colonies (Brandis et al., 2011). This study aimed to link stable isotope values of 13C and 15N found in juvenile waterbird feathers with known dietary intake. Dietary intake was calculated using scats (faecal matter) collected at nest sites throughout the nesting period. Prey items were identified from body parts in the scats and analysed for 13C and 15N. We calculated the percent contribution of dietary items using source mixing calculations and isotope values at each sample time. These data showed that terrestrial invertebrates were the major source of prey items and the contribution of specific invertebrate groups changed over time throughout the breeding event. The results of this study found that ibis are opportunistic feeders taking advantage of different prey items as they become abundant in the landscape. The results of this study significantly contribute to our understanding of waterbird feeding ecology and the role of waterbirds in the food web.