The harvesting of sooty shearwaters, muttonbirds or tītī is divided into two stages: nanao, when chicks are extracted from their burrows; and rama, when they are caught above ground under torchlight.
The nanao period usually lasts from 1 to 22 April, although this may vary from year to year and between islands.
Muttonbirders work during daylight to take chicks from their burrows. Each burrow holds a single chick. Harvesters lie on the ground and reach into the nest chamber to catch and carefully manoeuvre the chick out. If it cannot be reached from the entrance, muttonbirders sometimes dig a hole and pull it out. Great care is taken to seal the hole with a puru (earthern plug) to prevent water from entering the chamber or collapsing it.
Once the chick is removed from the burrow it is quickly killed and pressure is applied to its abdomen so it regurgitates any proventricular oil or stomach contents. Some muttonbirders then plug the throat with feathers or dirt to stop any remaining stomach contents leaking out and soiling the feathers, as this makes plucking difficult.
The rama period can last from mid-April until 31 May, but harvesting usually stops by 15–20 May because most chicks have fledged and left the islands. The moon and the weather largely govern harvesting during this period.
Muttonbirders work at night by torchlight or with lanterns to catch chicks when they emerge from their burrows to exercise their developing wings. Chicks prefer to come out on dark, moonless nights, especially when there is wind and rain. In such conditions, muttonbirders are able to catch the most birds in the least time.