A small, elegant petrel that looks like someone washed a prion in pale blue dye and forgot to rinse. The upperparts are a soft blue-grey. The cap is darker. The tail is banded in black and white. It is beautiful in a quiet way. The kind of beauty that does not announce itself. You have to look closely. The observation requires attention. The reward is subtle. The name is slightly misleading. The blue petrel is not blue in the way a kingfisher is blue. It is blue like a distant mountain or a winter sky. A hint of colour rather than a statement. The white rump and dark tail tip help with identification. In flight, it moves with the typical prion-petrel mix. Rapid wingbeats alternate with glides and sudden changes of direction. The movement is erratic. The control is precise. Feeding involves crustaceans, small squid, and fish. Like the prions, it uses a filtering bill to strain copepods and krill from surface water. The bill is short and broad. It is fringed with lamellae. It flies low, pattering across the wave tops. The head is submerged. It filters as it goes. A specialised tool for a specialised diet. The efficiency is high. The method is unique. Breeding takes place on some of the most remote islands on Earth. South Georgia. The Prince Edward Islands. The Crozets. And New Zealand's subantarctic groups. The burrow is dug into deep soil on a well-drained slope. A single white egg is laid. Incubation takes about fifty days. It is shared between the parents. The commitment is equal. The effort is sustained. The chick hatches in December or January. It is covered in thick grey down. It grows rapidly. It is fed on regurgitated krill oil and stomach oil. The oil is energy dense. A single feed can sustain the chick for days. That matters when the parents are six hundred kilometres away. They forage in Antarctic waters. The distance is significant. The provision is critical. Blue petrels are circumpolar. They follow the Antarctic Convergence. This is where cold southern water meets warmer northern currents. That line is rich in krill. The petrels know this. They feed there year-round. They only return to land to breed. A life spent at the edge of the ice. The existence is pelagic. The connection to land is brief. In New Zealand waters, blue petrels are common but seldom seen from land. They pass the subantarctic islands in large flocks during the breeding season. At sea, they mix with prions and other small petrels. Distinguishing them requires patience and good light. The blue-grey back is the clue. Everything else is white, black, or grey. The identification is difficult. The observer must be skilled. The bird remains elusive. It carries on.