Contribution of an urban green space to the success of the Ariel toucan reintroduction in an Atlantic Forest National Park

Abstract Urbanization is one of the most enduring transformations in land use, resulting in often irreversible habitat loss and fragmentation, which are key drivers of defaunation. However, the impact of urbanization varies depending on the native vegetation remaining within urban areas. In the city of Rio de Janeiro, Brazil, urbanization has led to biodiversity loss but the city still has a significant coverage of green areas and remnants of Atlantic Forest. This includes the Tijuca National Park, which has been the focus of reintroduction projects to restore native fauna. The first of these was of the Ariel toucan Ramphastos ariel in 1970, which has established well. Flocks are now often seen in the city’s green spaces but no monitoring has been carried out since the reintroduction. Here, we seek to understand how the reintroduced population is utilizing urban green areas for feeding and reproduction, which are key indicators of reintroduction success. We characterized frugivory in the Rio de Janeiro Botanical Garden over 290 weeks during 2017–2023, using the feeding bouts method. We recorded 850 observations of toucans feeding on the fruits of 91 plant species. We also assessed reproductive success during two breeding seasons, monitoring 29 fledglings in 10 nests. Nests in tree cavities were re-used in both breeding seasons, by different nesting birds. We conclude that this urban green area provides breeding sites for the R. ariel population and food resources year-round. Our results corroborate the potential of urban green areas to support biodiversity and contribute to the success of reintroduction projects in cities.