It digs its burrows on gentle to steep mountain slopes at 1,200-1,800 m, under tussock grass or low alpine scrubland (Marchant and Higgins 1990). First breeding is thought to occur at 4-6 years of age. It feeds mostly on small fish and krill (Heather and Robertson 1997). Birds gather food for chicks as far south as the Otago Peninsula and often fish around Banks Peninsula bays (Harrow 2009). Kapiti Island and Cook Strait are common feeding areas in the north and they have been recorded near the Chatham Islands (Harrow 2009). Frequently diving to feed at c.25 m, they have been recorded as deep as 36.6 m (Harrow 2009). Burrow occupancy levels in both original colonies in 2006/2007 was found to be similar to the 1990s. In contrast, breeding success in both main colonies was thought to be due to poor at-sea feeding conditions, rather than increases in stoat predation, due to a lack of evidence pointing to the latter (Sommer et al. 2009). Annual adult survival, breeding success, and burrow occupancy averaged 93%, 47% and 71%, respectively (Sommer et al. 2009). Low levels of breeding success, particularly at Shearwater Stream colony, point to the possibility of the colony levels being maintained by immigration from the more successful Kowhai Valley colony (Sommer et al. 2009).