Pardela Cenicienta (atlántica) vs Pardela Cenicienta (mediterránea)

Cory's Shearwater and Scopoli's Shearwater are closely related and can be challenging to distinguish at sea. The most reliable field mark is the underwing pattern: Scopoli's Shearwater shows more extensive white on the underwing, especially in the primary feathers, compared to Cory's Shearwater.

Focus on the underwing pattern: look for more extensive white in the primaries of Scopoli's Shearwater. Be cautious as lighting and distance can affect perception of these differences.

Scopoli's Shearwater has more extensive white on the underwing, particularly in the primary feathers, whereas Cory's Shearwater has less white, giving a more uniform dark appearance.