A seabird the size of a small apple dives like a penguin and flies like a bullet. The common diving petrel is the smallest of the diving petrels. It is one of the most extraordinary birds you have probably never heard of. It weighs about the same as a tennis ball. It dives to depths of twenty metres. It swims underwater using its wings. It is a penguin in miniature. It does not get the attention it deserves. The neglect is undeserved. The bird is remarkable. The plumage is black above and white below. A dark cap covers the head. A white stripe runs along the side of the face. In flight, it looks like a tiny shearwater. It whirrs low over the waves. Then it folds its wings and drops into the water. The transition is instant. One moment air. The next, water. The boundary is crossed without hesitation. The bird belongs to both elements. It masters neither completely. It survives in the interface. It feeds on crustaceans, particularly krill and copepods, plus small fish. It pursues them underwater. It paddles with its wings. It steers with its feet. A diving petrel beneath the surface is fast, agile, and silent. It catches prey in its bill. It surfaces. It swallows. It dives again. The cycle is rapid. The efficiency is high. The bird does not waste movement. It does not waste time. It hunts with purpose. The wings are short and powerful. They are adapted for underwater propulsion. On land, they are almost useless. The bird cannot fly from flat ground. It needs a slope or a cliff edge to launch. A diving petrel that lands on a beach is stranded. It waddles. It struggles. It waits for the wind. The limitation is severe. The bird accepts it. It avoids the beach. It stays on the slopes. It stays near the edge. Breeding takes it to remote islands and coastal headlands. The burrow is dug into soft soil. Sometimes it is a metre deep. A single white egg is laid. Both parents share incubation. The chick is fed on regurgitated crustacean oil. It is energy-dense and efficient. It fledges in about fifty days. The growth is steady. The care is shared. The investment is significant. The colonies are nocturnal. The birds return to their burrows after dark. They call to each other. The sound is a low, purring moan. It is repeated at intervals. On a dark night on a subantarctic island, a diving petrel colony sounds like a crowd of ghosts. The atmosphere is eerie. The noise is constant. It marks the presence. It signals life. In New Zealand, the common diving petrel breeds around the South Island coast. It breeds on many offshore islands. The subantarctic populations are enormous. The birds are common. They are also invisible to most people. A small, dark bird that dives before you see it. The name 'kuaka' is shared with the godwit. Different bird. Same name. The early settlers heard a call. They applied a familiar word. The diving petrel does not mind. It carries on.