Berta maggiore/boreale vs Berta dell'Atlantico

Cory's Shearwater and Great Shearwater can be distinguished primarily by their head and belly markings. Cory's Shearwater has a more uniform head and lacks the dark cap and brown belly-patch that are characteristic of the Great Shearwater.

Look for the dark cap and brown belly-patch on the Great Shearwater. Cory's Shearwater will have a more uniform appearance without these distinct markings.

Cory's Shearwater has a more uniform head, while the Great Shearwater is marked by a distinct dark cap and a brown belly-patch. The underwing of the Great Shearwater is white with variable brown markings.