72 | Chapter 4
before continuing south to spend the winter in the Benguela Current.
On the return migration, the initial phase is rapid; 6,000 km covered at
800 km/day takes the birds to a stopover region off Morocco, Maurita-
nia, and Senegal. The time spent thereabouts is 19 days, much less than
is spent in the different Biscayan stopover region in autumn. Then, from
west Africa, the birds fly fairly directly to Greenland to round off a
30,000 km round trip – and that impressive total excludes local mean-
dering in the Benguela region. Why Sabine’s Gulls eschew the chance to
benefit from following winds, a tactic used by other species, is not obvi-
ous. How seabirds often exploit prevailing wind patterns to minimize
the costs of their travels is the subject of Chapter 6.
***
Seabirds are paragons of fidelity. Normally, the two members of a pair
will continue to breed together until death do them part. Numerous
studies have shown that this fidelity is rewarded by increased breeding
output. Conversely, divorce is costly, not least because it may take sev-
eral years until another partner is found, and those are wasted, chick-
less years.
It is not unknown for bird pairs to remain together on migration.
Geese and swans achieve this romantic trick, and remain together with
their youngsters on the wintering grounds, having perhaps migrated en
famille from Siberia. This enables researchers to assess the breeding suc-
cess of known pairs without ever needing to venture to Siberia.
The temptation therefore to wonder whether seabirds might also re-
main together on migration is strong. But, oh, the difficulties. Think of
a thousand gannets arrowing into the water to feast on a mackerel shoal.
While the male gannet finds himself sitting on the water, trying to swal-
low a large, lively and not- to- be relinquished fish, his mate wanders away
with the crowd because she has yet to catch a fish. Imagine the hours of
darkness when the breaking waves of a stormy sea and the keening of
the cold night wind render maintaining contact by sight or sound over-
whelmingly difficult. It seems improbable that pairs could maintain
contact; yet the ability of young auks to remain with their parents over
periods of weeks argues that the improbable might turn out occasion-
ally to be true. Alas, it is a truth yet to be demonstrated.