Kaka poria are leg rings crafted from bone or stone used to keep pet kaka parrots from flying away. The giant kaka parrot was used by the Maori to assist them during the hunt. Wikipedia has more info on the Kākā, (Nestor meridionalis)
The bird was used as a decoy to capture other kaka parrots. As with many Maori items the kaka ring was both used as a tool as well as jewelry. The Maori wore the rings as pendant necklaces or earrings.