Sympatric cranes in northern Australia: abundance, breeding success, habitat preference and diet

Sympatric breeding of Sarus Cranes (Antigoneantigone) and Brolga (A. rubicunda)occurs only in northern Queensland, Australia but factors contributing to thisunique sympatry are unknown. Large-scale developments currently planned in thisregion, with potentially major impacts on cranes, create an urgent need to understandthe ecological requirements of each crane species. We carried out a multi-floodplainlandscape-scale survey during April-May 2017 and derived metrics for several ecologicalaspects for the first time for both crane species. The abundance of the twospecies differed between the floodplains. Both crane species synchronisednest-initiation with rainfall (November to March). Breeding success was higherthan past estimates anywhere, with 60% of Sarus Crane pairs and 50% of Brolgapairs fledging chicks. Sarus Cranes preferred four riverine Eucalyptus-dominated regionalecosystems, with 10% using open habitats. Brolgas preferred two non-woodedregional ecosystems, but 32% shared Eucalyptus-dominatedregional ecosystems with Sarus Cranes. Stable isotope analyses revealed Sarus dietto be comprised of more diverse vegetation than Brolgas, while Brolgas fed acrossa wider range of trophic levels. The ecology of Gulf cranes closely matchedhabits of Sarus Cranes in south Asia, despite disparate conditions suggestingconsiderable species plasticity. The diverse habitats of the Gulf and varying dietappear to facilitate the cranes’ sympatry, and our study provides basic datafor developing long-term conservation plans in the face of developmentactivities.