The dark-morph Herald Petrel Pterodroma heraldica

Summary. Whether dark-morph Herald Petrel Pterodroma heraldica exists or not has been debated for many years. We summarise previous contributions on the subject, provide indisputable evidence of the dark morph, describe its plumage based on museum specimens and live birds, highlight differences between dark, light and intermediate morphs, and enumerate characters that relatively easily separate the dark morph from ‘all-dark’ Henderson Petrel P. atrata. Dark-morph Herald Petrel is scarce and local. Since the 1970s, records have been restricted to the central South Pacific at Mangareva Island (Gambier Islands) and Ua Pou (Marquesas Islands).