Appearance and feeding
Shearwaters are long-winged birds that typically fly in broad sweeping arcs, slicing through the air just above the sea surface. They have long, slender, hook-tipped bills, which they use to seize fish, crustaceans and squid. They mostly feed by plunging into the water from less than a metre above the surface. Once underwater they use their half-extended wings to pursue fish and squid. The sooty shearwater regularly dives to depths of 60 metres.
Shearwaters are some of the most abundant seabirds. Many millions of sooty shearwaters breed on islands in southern New Zealand, although numbers are declining. In southern New Zealand, Kaikōura and the outer Hauraki Gulf, huge flocks of shearwaters can often be seen feeding in tight groups close inshore. Ten species breed in New Zealand.
Buller's shearwater (Puffinus bulleri), which breeds only in New Zealand, has characteristics unusual in a shearwater. For their size they are light in weight, with soft plumage. Instead of diving, they feed while sitting on the water’s surface, reaching down with their long necks. This species breeds only on the Poor Knights Islands but may be seen around much of New Zealand. The birds migrate to the North Pacific.
Appearance and feeding
Petrels in the genus Procellaria are heavy-set birds that feed at the surface or make shallow dives. They also scavenge waste from fishing vessels. This extra food has benefited the Westland petrel (Procellaria westlandica) whose population appears to have increased. However, fishing boats pose a threat to grey petrels (Procellaria cinerea) and other species, which get caught by tuna long-line vessels.
Two species are endemic to New Zealand and now have very restricted breeding ranges. The black petrel (Procellaria parkinsoni) breeds only on Great Barrier and Little Barrier islands, and the Westland petrel only near Punakaiki, although in the past the black petrel also bred in other parts of New Zealand. The other species breed on subantarctic islands in the New Zealand region and elsewhere.
The Westland petrel and white-chinned petrel (Procellaria aequinoctialis) are the largest burrow-nesting species. Both weigh over a kilogram and their burrows are large, dank and cavernous.
Good news for southern petrels
In 2001, Campbell Island (700 kilometres south of the South Island) became the largest island in the world to have rats eradicated. Arriving on sealing vessels in the 19th century, Norway rats multiplied and ate their way through colonies of burrowing and crevice-nesting petrels. Now the rats have gone, remnant bird populations are likely to get bigger.
The fulmars and their kin are the least specialised of the petrels. They have broad diets and use a wider range of feeding methods than other petrels, but are restricted to surface or near-surface prey. All are enthusiastic scavengers. Giant petrels (Macronectes spp.) even come ashore to feed on dead whales or seals, offal or carrion close to the water’s edge, and they sometimes prey on smaller seabirds. Cape petrels mostly eat small plankton.
Distribution and breeding regions
Fulmarine petrels typically live at high latitudes, but two species, the northern giant petrel (Macronectes halli) and the Cape petrel, are commonly seen around much of New Zealand. Both of these are more numerous in the south than the north, and both breed on the Chathams and some of New Zealand’s subantarctic islands. Giant petrels breed on open ground, while the other fulmars breed in crevices or on cliff ledges.