76 | Chapter 4
the area chosen was rich in food, be it natural or fishery waste. We might
bet on a prudent petrel choosing such an area.
While some penguins are adrift in the vastness of the Southern Ocean
when not breeding, that is not true of Gentoo Penguins satellite- tracked
from South Georgia. British Antarctic Survey researchers reported that
“five penguins tracked from Bird Island [South Georgia] remained close
inshore, and although they did not return to the initial tagging site, they
did appear to return to land each evening. They made diurnal trips to
sea of similar distance from land as those during the breeding season,
even though the constraints of chick rearing were absent.”^32 It was en-
tirely business as usual.
Perhaps the most striking contrast between breeding season and non-
breeding season daily routines has emerged from species which, outside
the breeding season, sever their link with terra firma. Here the combina-
tion of moult, possibly impaired flying ability, the need to conserve en-
ergy, and the possibility that migration has taken the bird to a rich
feeding area would all point towards relative inactivity. Take the case of
South Polar Skuas.^33 Migrating northwards and returning southwards,
they spend a little less than half the 24 hours in flight – and therefore
just over half the entire day sitting on the water. But when they reach
their destination, say the Seychelles or the Bay of Bengal, they may spend
virtually all night on the water and a mere 15 percent of the daylight
hours in flight. Such a low activity life- of- Riley could be the result of
impaired flight or because food was easily acquired or both; with the
skuas, we do not know which.
A comparable contrast between activity patterns during the breed-
ing and non- breeding seasons has been discovered in several medium-
sized petrels, for example White- chinned and Chatham Petrels which
remain in the Southern Ocean when not breeding. Tommy Clay and I
uncovered just the same contrast in the Murphy’s Petrels we studied.
When off- duty during incubation and making trips of 10,000– 15,000 km
around the South Pacific (Chapter 5), they spend around 95% of their
time at sea in flight. Their activity levels cannot be faulted. But when
Murphy’s Petrels are passing the non- breeding season, the (northern)
winter, in the North Pacific, 80 percent of darkness and 60 percent of