What influences where birds choose to nest? About 15% of Australian birds, or 114 species, need tree hollows for breeding or shelter. The number of hollow-bearing trees is declining due to timber harvesting and development, and competition is stiff in the animal world for these increasingly rare tree hollows. Non-native species and increasing urban numbers of natives such as rainbow lorikeets are changing the community dynamics of hollow-nesting species. Critical to conserving the range of hollow-nesting native birds is understanding how these interactions operate when it comes to who gets to nest and where. This has been the topic of Andrew Rogers’ PhD research at The University of Queensland. He explains how his research on the drivers of nesting competition can help us effectively manage invasive hollow-nesting species and improve the outlook for threatened native ones.