Scientific support invited by Indigenous peoples and local communities (IPLC) to assist with customary environmental management can improve conservation and community livelihoods. For example, demographic models can help to understand how alternative wildlife management strategies affect population dynamics and harvest sustainability. We developed a demographic model to assist Ngāi Tahu, the southern-most Māori tribe in Aotearoa/New Zealand, in customary management of a culturally important population of Black Swans (kakī anau, Cygnus atratus).