Abstract

There has been a long-standing debate about the post-hatching mode of development of the Great Auk’s Pinguinus impennis single chick. Did it show an ‘intermediate’ pattern, leaving the colony at around one quarter of the adult’s weight like its closest relatives the Razorbill Alca torda, Common Guillemot Uria aalge and Brьnnich’s Guillemot U. lomvia, or was it precocial, leaving the colony only a few days after hatching, like the more distantly related murrelets? The precocial idea originates from Martin Martin’s (1698) account of when Great Auks arrived (‘first of May’) and departed (‘middle of June’) from St Kilda – a period of no more than seven weeks. With an incubation period of around 40 days, this means that the chick must have left very soon after hatching – hence the idea that it was precocial. A re-reading of Martin’s account reveals that it has been misinterpreted. The St Kildans took all the Great Auk eggs each spring and the birds did not relay. As a result, the adults would have left the colony much earlier than if they had chicks to rear. On the basis of this and other evidence, it now seems much more likely that the development of the Great Auk chick was intermediate, like that of its closest relatives.