taking the PlUnge | 33this period.^7 Males made almost twice as many dives as females, on aver-
age 104 versus 57 per day, a measure of the extra work involved in find-
ing the extra food needed by the growing chick. In addition the hard-
working males tended to dive deeper (49 m) than females (36 m). Then,
just over two months after fledging, male and female foraging effort
equalised, presumably because the young bird was thereafter able to
look after itself.
Why responsibility for the chick devolves solely to the male at this
stage remains a mystery. After the female has necessarily done all the egg-
laying, it does mean that the total contributions of mother and father
to rearing their chick become more equal – but this explanation seems a
tad vacuous.
Not all guillemots and Razorbills spend these months of father- chick
togetherness in a single area. As the northern winter approaches, there
may be advantages in heading south. This is what Brünnich’s Guillemots
from south- west Greenland do. Rather than make the journey by flying,
which is energetically exhausting for the small- winged males and down-
right impossible for the chicks, they swim south together. Imagine the
difficulties for small birds of keeping in contact on such journey when a
one metre swell will be towering and a 10 metre swell beyond towering.
Again using a combination of geolocators and immersion recorders,
Jannie Linnebjerg of Lund University found that male Brünnich’s Guil-
lemot parents and their chicks achieved the autumn journey southward
of almost 3,000 km entirely by swimming. Further highlighting the en-
ergetic advantages of swimming, females and non- breeding males flew
only the first 800 km of the journey. The remaining 2,000 km were swum.
Other seabirds might aspire to the aerial route to departure and in-
dependence, only to fail in their aspiration. Black- footed Albatrosses
leaving their colonies in the north- western Hawaiian Islands are fully
feathered and potentially able to fly but, if they falter and land in the
turquoise lagoons surrounding the colonies, they risk becoming lunch
for Tiger Sharks. Further north in the Pacific, young Short- tailed Alba-
trosses take time to take wing. After leaving the colony, the fledglings
typically make short flights and mostly ‘drift’ on the sea at walking
speed (< 5 km/h) for an average of nine days. Only after this period do