taking the PlUnge | 35has unquestionably been at the forefront of modern pioneering seabird
research. As the years have passed and the sinews stiffened, Weimerskirch
has shrewdly shifted his own research from the petrels of the Southern
Ocean towards the frigatebirds of the tropics. Accordingly his clothing
has shifted from parka to floral shirt. At the 2015 2nd World Seabird
Conference in Cape Town, he described how Great Frigatebirds under-
take a protracted transition to independence, competent flight, and spe-
cialised feeding which may involve catching flying fish at the sea’s surface
or harrying other seabirds into disgorging their food in flight, and then
catching the vomited meal even before it has fallen to earth or water.
The juvenile Great Frigatebirds hailed from Europa, a low atoll be-
tween Mozambique and Madagascar. For the first six months of flying
life, the juveniles go to sea by day but return to land by night to be fed,
normally by their mothers. Then the satellite- tracked young birds move
north up the Somali coast, perhaps looking down on the region’s con-
temporary human pirates. The journeys are relaxed, around 450 km/day.
The birds alternate periods of soaring in circles, attaining heights up to
3,000 m, and periods of slow descent. While soaring, the frigatebirds do
not flap their wings but rely on differences in air speed between differ-
ent blocks of air to gain height, so- called dynamic soaring. Using this
tactic, the young frigatebird remains in flight for up to two months at a
stretch,* sometimes even passing close to but not making landfall on the
scattered islands of the Indian Ocean. Only occasionally is the pattern
broken with land- based rests of a day or so on isolated islets of the Sey-
chelles or Chagos archipelagoes.^9 As the young birds pursue repeated
clockwise circuits of the Doldrums of the central Indian Ocean for a
year or more, it is an immensely leisurely entrée to independent life.
Some young seabirds evidently take weeks or months to break the
link with their parents. This may be due in part to the time taken to
hone feeding skills, a process potentially taking months or years, as will
be explored further in the next chapter. But the acquisition of flying
skills is likewise not trivial. On the other hand, the very rapid, very long-
distance journeys to be described later in this chapter suggest, for some
species, those flying skills are adequate or better from the get- go.
- (^) For eight juvenile birds, the average maximum time spent aloft was 41 days.