In this research project, Hauraki traditional knowledge concerning the harvest of oi (oi, grey-faced petrel, Pterodroma macroptera gouldi) on the Ruamaahua (Aldermen) Islands was recorded and analysed. The harvest of oi linked Hauraki individuals to culture, ancestors, individual well-being and tribal identity. It also maintained mana, kaitiaki responsibilities and traditional knowledge systems. Daily catch rates of oi chicks (and number of birders) have declined in some circumstances by as much as 87% between 1950 and 2007.