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Cory’s Shearwater (Calonectris diomedea)

Many of the important events in the Cory’s Shearwater’s life happen at night. This is the time when it usually feeds, snatching fish and squid from the surface of the water, either while swimming or in a quick plunge from flight. And it’s also the time when breeding adults attend their colonies; these are usually on rocky islands but can also be up to 30km inland among hills and mountains. The birds gather in huge flocks at dusk, and then fly to their burrows among boulder fields or soil under cover of darkness. While gathering they make remarkable sobbing wails, audible from a great distance, but as soon as they reach their holes they fall silent.

The burrow is often about a metre long and, presumably to protect the youngster inside, tends to dog-leg to the right. In common with the pattern for other shearwaters, the young Cory’s is left alone as soon as it is old enough to regulate its body temperature; this allows both parents to find food for it. It soon fattens up until it is much heavier than the adult birds. Towards the end of its fledging period the parents begin to bring less and less food, and eventually may abandon the youngster altogether. By then it is ready to depart on its first flight, alone and at night.

This is a large, powerful shearwater, at ease with strong winds and heavy waves. After breeding it may wander across the Atlantic Ocean as far as the Eastern Seaboard of the USA. At this and other times many individuals make a habit of following the movements of predatory fish or dolphins, mopping up the prey species as they flee.