166 | Chapter 9
Arctic Circle or yet further north experience minimal daylight, hinting
they must do some feeding during darkness. Among the gadfly petrels
are species that have barely ever been seen feeding, perhaps because they
mostly or only do so at night. And many albatrosses and petrels are
primarily squid eaters. Since many squid species come closer to the
surface at night – they migrate vertically on a daily basis – they could
be easier to catch at night, especially if lit by their personal array of
nightlights, their bioluminescence. That argument in favour of noctur-
nal feeding by the birds is only relevant if the squid are caught alive. If
squid are caught dead, then it matters little to the bird whether they do
or do not migrate vertically and whether they are bioluminescent, pro-
vided they float when dead and do not sink into the depths. And, fi-
nally, early activity recorders deployed on some more aerial species*
showed they spent more time on the water by night than by day. Because
they fed on the water at night, or because they simply rested on the
water at night?
It would be fair to say that the topic was besmirched with uncer-
tainty until more direct evidence became available. Early information
emerged in a paper by Henri Weimerskirch and Rory Wilson with the
admirably helpful title ‘When do Wandering Albatrosses forage?’.^3 The
answer from stomach temperature sensors was clear; 89 percent of
food (by weight) was ingested by day when the Wandering Albatrosses
are mostly flying, and the remaining 11 percent at night when half the
time or more is spent sitting on the water. For the breeding Wanderers
it turns out that hunting tactics tend to be rather different by day and
by night.
Although the difference is not absolute, the daytime tactic mostly in-
volves flying and grabbing food whenever and wherever it is encountered.
The most likely distance between such encounters is 10– 100 km. And it
appears this Wanderer daytime strategy is shared by Laysan Albatrosses.
Heading out from Oahu (Hawaii), chick- feeding Laysan Albatrosses
carried camera and GPS loggers. Twenty returning birds delivered
- (^) The less aerial species such as auks, and of course penguins, spend virtually the entire 24 hours
on the water outwith the breeding season.