Check Your Mate

King Penguins breed en masse at sub-Antarctic islands, with most pairs occurring in vast, sprawling colonies.

- Peter Ryan

How seabirds find – and keep – their mates in these teeming crowds that sometimes number tens of thousands of birds has long fascinated biologists. King Penguins face an additional problem compared to most seabirds because they lack a fixed nest site. Adults incubate on their feet and so a partner could shuffle some distance from where it was entrusted with the precious egg at the end of the previous incubation shift.

Before a King Penguin can attempt to breed, it obviously needs to find a mate. A recent paper by a group of French researchers (Kriesell et al. 2018; Ibis, doi: 10.1111/ibi.12577) explored how King Penguins tell potential mates from rivals.

In this species, size differences are at best subtle and, like most seabirds, it lacks obvious plumage differences between the sexes. Some studies have claimed to detect sex-specific differences in the penguins’ striking orange head patterns, but Kriesell and colleagues found no such variances. The females are on average slightly smaller than the males, with bill length providing the best clue to sex, correctly identifying almost 80 per cent of individuals.