Sympatric Cranes in Northern Australia: Abundance, Breeding Success, Habitat Preference and Diet

Sympatric breeding of Sarus Cranes (Antigone antigone) and Brolga (A. rubicunda) occurs only in northern Queensland, Australia but factors contributing to this unique sympatry are unknown. Large-scale developments currently planned in this region, with potentially major impacts on cranes, create an urgent need to understand the ecological requirements of each crane species. We carried out a multi-floodplain landscape-scale survey during April-May 2017 and derived metrics for several ecological aspects for the first time for both crane species. The abundance of the two species differed between the floodplains. Both crane species synchronised nest initiation with rainfall (November to March). Breeding success was higher than past estimates anywhere, with 60% of Sarus Crane pairs and 50% of Brolga pairs fledging chicks. Sarus Cranes preferred four riverine Eucalyptus-dominated regional ecosystems, with 10% using open habitats. Brolgas preferred two non-wooded regional ecosystems, but 32% shared Eucalyptus-dominated regional ecosystems with Sarus Cranes. Stable isotope analyses revealed Sarus diet to be comprised of more diverse vegetation than Brolgas, while Brolgas fed across a wider range of trophic levels. The ecology of Gulf cranes closely matched habits of Sarus Cranes in south Asia, despite disparate conditions suggesting considerable species plasticity. The diverse habitats of the Gulf and varying diet appear to facilitate the cranes' sympatry, and our study provides basic data for developing long-term conservation plans in the face of development activities.