Kahukura (red cloak) butterflies are a beautiful taonga species whose striking colours make it easily identifiable in the wild. The butterflies are most commonly seen in the summer months, often feeding on nectar from hebe or other flowering plants, or basking in sunny areas (this is when you see them with their wings open). Adult females lay their eggs on ongaonga|stinging nettle (preferring the native Urtica ferox), and the caterpillars feed on the leaves of that plant. The adults overwinter in a state of reproductive diapause and come out on rare sunny days to feed. To encourage these butterflies to visit your garden, consider growing a few nettles where people won’t easily blunder into them along with flowering plants for the adults to get nectar.
While they are often seen foraging on the nectar produced by flowers, they can also be observed drinking water and foraging on sap exudes. In fact, when competing for sap exudes, they have been observed fighting (and winning) competitions with social wasps (Vespula) over the resource.
Check these links for more info on Kahukura in NZ
Wikipedia: Information on Kahukura
Click on the image to visit the official iNaturalist.nz observation.