Manx shearwaters leave breeding colonies and winter mainly in which ocean?

Manx shearwaters leave their breeding colonies and winter mainly in the South Atlantic Ocean. Their northern breeding grounds include islands around the United Kingdom, Ireland, Iceland, the Faroes, and the Azores, but the birds spend the non-breeding season far to the south.

From roughly July to March, many Manx shearwaters winter off Brazil and Argentina; smaller numbers occur off southwestern South Africa. Their southbound journey can exceed 10,000 kilometres, an extraordinary distance for a bird weighing only about 350–575 grams. Young birds make their first migration without their parents.

The species is often confused with other shearwaters because several relatives also cross oceans. Manx shearwaters are especially distinctive for their stiff-winged, low flight, in which they appear to “shear” across the waves. They return to island burrows at night to breed, and adults may commute as far as 1,500 kilometres to reach feeding waters.