Great Shearwater, puffinus gravis

The Great Shearwater (puffinus gravis) is a large shearwater in a seabird family called Procellariidae. There is unclear evidence of its relationships. The Great Shearwater belongs to a group consisting of large species that can be distinguished as genus Ardenna; within these, it might be associated with the other blunt-tailed black-billed species Short-tailed Shearwater and particularly the Sooty Shearwater. On the other hand, it could be a monotypic subgenus (ardenna sensu stricto), a representative from the Atlantic of the light-billed Hemipuffinus group made up of the Pink-footed Shearwater and the Flesh-footed Shearwater.

Much like the Sooty Shearwater, this shearwater follows a circular type route moving up the eastern seaboard of first South, then North America before crossing the Atlantic in August. It is quite common off the south-western coasts of Great Britain and Ireland before going back to the south again, except this time it is down the eastern littoral of the Atlantic.

This bird breeds on Nightingale Island, Inaccessible Island, Tristan de Cunha and Gough Island. It’s one of the few bird species that migrate from breeding grounds in the Southern Hemisphere to the Northern Hemisphere, being that the normal pattern is the other way around. They nest in large colonies, laying one white egg in a shallow burrow or even in the open grass. Their nests are only visited at night, avoiding predation by large gulls.

The approximate length of this bird is 43 to 51 cm, and the average wingspan is 105 to 122 cm. It can be identified by its size, dark upperparts, and white under parts except for a brown belly patch and dark markings on the shoulders. It has a black cap, a white “horseshoe” on the base of its tail, and a black bill. Its stiff flight, like the large Manx Shearwater is also distinctive. The all-dark Sooty Shearwater is the only other large shearwater in its range. This bird inhibits the typical “shearing” flight of the genus, dipping from side to side with stiff wings and a few wing beats. The tips of the wings almost touch the water when flying in this fashion. The flight is direct and powerful, making the wings stiff and straight.

They typically feed on fish and squid. They catch it from the surface or they plunge-dive. It cautiously follows fishing boats, where it indulges in a noisy squabble. This is an expressive species and can be seen in large numbers from appropriate headlands or ships. Their call is a piercing eeyah cry usually called when nesting or resting in a group on the water.

Image Caption: Greater Shearwater, Puffinus gravis, Location: Gulf Stream off of Hatteras, North Carolina, United States. Credit: Patrick Coin/Wikipedia  (CC BY-SA 2.5)