102 | Chapter 5
That much can be learnt by observing the coming and goings of birds
at the colony. It does not illuminate whether the two trip types involve
different destinations.
Two nice examples, confirming that short and long trips do indeed
involve different destinations, come from the Southern Ocean. The
nesting stronghold of the Sooty Shearwater is New Zealand where un-
lucky parents may raise a chick that becomes a harvested muttonbird
served in a New Zealand restaurant.* When adult shearwaters with chicks
were tagged with geolocators, they mixed short 1– 2 day trips over New
Zealand waters, typically within 500 km of the colony, with 11– 14 day
trips to the far colder seas of the Antarctic Polar Front 2,000 km south
from the colony.^20
In terms of distance ventured the contrast between short and long
trips is even more extreme among the White- chinned Petrels nesting
on the Iles Crozet, the archipelago in the Southern Ocean. On short
trips lasting just over one day, the petrels’ average maximum distance
from the colony was 62 km, barely over the horizon. On long trips aver-
aging 8.5 days, they matched the Sooty Shearwaters and headed south,
a fast commute averaging 31 km/h to Antarctic waters almost 1,900 km
distant.^21 The homeward journey from these krill- rich seas was equally
rapid at 34 km/h.†
In the majority of seabirds, males and females are of similar size and
have equivalent roles in chick- rearing. That said, there are exceptions.
When the female Emperor Penguin returns to the colony to relieve her
mate after his display of winter fortitude caring for the egg, she guards
the newly- hatched chick for the next 3– 4 weeks. Conversely, in Rock-
hopper Penguins, the males are primarily responsible for guarding
small chicks.
Later in chick rearing, less expected gender differences have been
discovered. Boobies follow the relatively uncommon pattern of size di-
morphism also seen among hawks, skuas and owls. The female is the
larger, which may contribute to differences in sexes’ behaviour. In the
- (^) Rich, gamey, and delicious in my single experience.
† (^) That is just slower than Usain Bolt at full tilt, remembering that a 10 second 100 metre dash
equates to 36 km/h.