off Chatham Island, Massachusetts.
Until recently considered conspecific with C. edwardsii (see below) and C. diomedea, differing from latter in its usually darker, browner head (1); more extensive dark tip of underwing (no white bases on primaries) (2); larger size, as expressed by mean wing length of males#R, effect size of 4·6 (score 2); calls delivered in threes vs twos, and in diomedea the notes are longer and with a high-pitched hiccup between them (2). Molecular evidence supports this split in one study#R, but is equivocal in another, with further research being called for#R. Monotypic.
E Atlantic, breeding from Galicia (NW Spain) and Berlengas Is (off WC Portugal) W to Azores and S to Canary Is; outside breeding season ranges widely in Atlantic, but wintering mainly in upwelling systems of the Benguela and Agulhas Currents#R. Has bred occasionally in Mediterranean (Columbretes, Giraglia)#R; population of Almería apparently of this species, based on both morphometric and genetic evidence#R.
Food and feeding
Status and conservation
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