38 | Chapter 2
flesh, roughly half the weight of the Titanic. This torrent’s track is ini-
tially southward and eastward, thus avoiding the coast of Australia. Then
the birds turn north-west, passing both east and west of Fiji, and prob-
ably making fast progress across the tropics. If travelling at 50 km/h for
20 hours a day, progress could be around 1,000 km/day. Birds reach the
Sea of Okhotsk and the west end of the Aleutian chain in late April.
Huge numbers spend the northern summer in the Bering Sea.*
The picture just painted covers the mass of migrating shearwaters. It
does not specifically focus on the fledglings, and it remains troublesome
to gather data on the long- distance movements of smaller species, like
shearwaters, on their first migration. Because, even if they survive, the
birds will not return to the colony for several years, so the chance of
capturing them to retrieve a geolocator or GPS device is small. Satellite
tags are a better option, but are heavier. Nonetheless a satellite study of
Scopoli’s Shearwaters was able to assess the speed of fledglings starting
independent life and heading from their breeding colony off Marseille
towards the Strait of Gibraltar, and then south to the wintering area off
west Africa. Within the Mediterranean the youngsters and older birds,
both immatures and adults, travelled at about the same speed of 90 km/
day. On reaching the Atlantic the pace picked up and the fledglings
(240 km/day) travelled faster than the older birds (177 km/day). How-
ever this shearwater study by Clara Péron and David Grémillet remains
an exception.^12 The best information about those first long airborne
journeys comes from larger species, especially albatrosses.
Working on the sub- Antarctic Iles Crozet, Henri Weimerskirch and
his team tracked 13 juvenile Wandering Albatrosses by satellite teleme-
try during their first year at sea.^13 Leaving the island, the birds first spent
about five days drifting on the water. As soon as a southerly or south-
westerly wind started to blow, they took to the air and headed between
north and north- east. So consistent was this route choice that it was
likely genetically determined. Then, fairly quickly, the juveniles upped
their daily travel distance to some 600 km. This is the same distance adults
routinely cover in a day and was very probably linked to the attainment
- (^) The relationship between this curving trans- Equatorial track and the prevailing winds is
treated in Chapter 6.