wind and waves | 119them in the area where the food was encountered, potentially increasing
the chance of another encounter, especially if their food tends to occur
in clumps. And of course seabird food, be it a shoal of fish or a krill
swarm, tends to occur in clumps. Therefore, if the nematode worm
Caenorhabditis elegans with a mere 1,000 body cells can include area-
restricted search in its lifestyle, there is every likelihood that seabirds
also can. Indeed they do. The way scientists use this variation in be-
haviour to identify areas where tracked seabirds are finding food will be
discussed in Chapter 8. For now, the point is that the behaviour will
generate more convoluted tracks over the scale of hundreds of metres or
a few kilometres. In Wandering Albatrosses, this zigzagging associated
with area- restricted search occurs at a scale of about one kilometre – as
compared to the 100 metre scale of dynamic soaring – necessarily mod-
ifying the relationship between the albatross’s track and the wind direc-
tion.^12 This could have energetic consequences, as has been demonstrated
in Northern Gannets.
Courtesy of a research team led by Françoise Amélineau,^13 French
gannets from the colony on Île Rouzic, off Brittany, bore a trio of de-
vices – accelerometers, GPS and depth recorders – when setting forth to
collect food for their chicks. When these devices were retrieved, Amé-
lineau could calculate the amount of energy the gannets were dissipat-
ing at various stages of their journeys from Rouzic, the sole French gan-
netry. It transpired that the straightline journeys to and from the
feeding areas off south- west England were less costly, in terms of calo-
ries expended per minute, than the spells when the birds were twisting
and turning above fish below. Prior to this study, the extra costs of
twisting turning flight had been predicted from aerodynamic theory,
but the gannet work was a pioneering direct demonstration of the extra
cost of tortuosity.
***
Expanding the spatial scale once more, a breeding seabird is making a
succession of journeys back and forth to wherever it feeds. If these jour-
neys are modest, say up to 100 kilometres, then the potential for adjust-
ing the route between colony and the food to exploit large- scale wind