Corys Shearwater (Calonectris diomedea) Science Article 2
Although aberrant colourations occur in a great variety of animal species, their frequency of occurrence is low. Here, we report the first two observations of melanistic Cory’s Shearwaters Calonectris diomedea, in the Azores archipelago and on the Canary Islands. Because dark plumages may be associated with subordinate status within petrel flocks and ith increased conspicuousness, melanistic individuals would have increased difficulties in obtaining food compared with their normally coloured conspecifics. This phenomenon might explain why melanism seems to occur less frequently than other aberrant colour patterns in this group.
BRIED, J., FRAGA, H., MIRANDA, P.C. & NEVES, V.C., Marine Ornithology 33: 19-22