Buller's shearwaters return to the Poor Knights Islands in mid-September to court females and clean out their burrows before breeding (7). Nesting occurs in large, dense colonies (5), with egg-laying beginning in October (2) (7). The single white egg is incubated by both sexes for about 51 days, and most chicks fledge at around 90 days (5). The following April to late May sees the colonies departing once more for the north Pacific (5) (7). The diet consists of krill, small fish, squid and jellyfish (6), and birds have only recently started to scavenge fishing boat scraps (5).