104 | Chapter 5
Frigatebirds on the eponymous Indian Ocean island, famous for its
marching crabs and notorious for its Australian Immigration Detention
Centre, a French team deployed satellite tags and GPS trackers. In 2009,
there was no difference between the foraging journeys of males and fe-
males in the brood period but, in 2010 when feeding conditions were
poorer, the male frigatebirds’ trips lasted twice as long as those of fe-
males, and took the birds further from the colony (413 v. 194 km).^24 It
was almost as if the males were already easing out of any long- term
commitment.
As a generalisation, a parent seabird collecting food for its young
should strive to minimize transport costs and collect that food as near
to home as possible. Conversely, when the going gets tough, the tough
seabird must face going further. That line of thinking could apply at
several time scales. Over a period of days, local seas might be influenced
by weather and force the bird further afield. Across years, birds may
feed closer in one year and further in another, possibly poorer, year. If
the deterioration is long- term, perhaps because of climate change, a
colony could become untenable. Finally, because of the Ashmole halo,
there is the possibility that birds from larger colonies habitually feed
further afield than their counterparts at smaller colonies.
Chris Feare is a lucky man. Now in his seventies, he has long since
run out of fingers on which to count the number of times he has visited
the luxury ecolodge* on Bird Island, Seychelles. The island hosts half a
million pairs of Sooty Terns, also known as Wideawake Terns in cele-
bration of their unrelenting ‘wideawake’ shriek. When incubating birds
were GPS- tracked by Feare in 2014, he witnessed short- term changes
in foraging journeys. The terns’ off- duty shifts initially lasted 1– 2 days,
during which the birds covered 100– 200 km. Then there was an abrupt
change to 6- day off- duty spells when the birds scoured 2,000 km of
ocean. This incident coincided with a brief spell when sea surface tem-
perature dropped in the western Indian Ocean. Chris Feare did not
know whether this temperature fall affected the birds’ food supplies
directly or, alternatively, influenced the movements of tuna upon which
Sooty Terns depend to drive their small prey to the sea surface, and into
- (^) http://www.birdislandseychelles.com/ (accessed 14 June 2017).