| Cape Verde Shearwater differs from Cory’s Shearwater Calonectris borealis and Scopoli’s Shearwater Calonectris diomedea in several ways including some clearly illustrated in the pictures below:
Size and structure
Considerably smaller (ca 10% in wing-length).
Wings relatively narrower, more pointed and often held in flight with the arm angled forwards.
Tail relatively narrower, longer and more wedge-shaped.
Head smaller.
Bill slimmer.
Overall a much smaller, slimmer, more angular bird.
Plumage
Nearly always shows a prominent broken eye-ring (the others can sometimes show this, but not usually so prominently).
Darker wing-coverts and primaries usually form a “W” across the upper-parts in flight – more obvious than the others.
Primary underwing pattern as in borealis, lacking white inner webs of diomedea.
Sometimes a fairly clear demarcation on the side of the face below the eye and ear-coverts resulting in a capped effect.
Does not have a greatly contrasting paler head, hind neck and mantle.
Soft parts
Bill grey with a dark tip, sometimes tending to yellowish or pink. A few birds are distinctly yellow, but never as bright as diomedea or lurid as borealis.
Legs pink, as in the others.
All these birds are in an advanced state of primary moult (primary moult score anywhere between 10 and 40). As the young do not fledge until late October or November, these are probably immature non-breeders.
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Cory's Shearwater
Senegal October 2001
