158 | Chapter 8
clusters, there was no obvious division of the trip into commuting and
feeding phases. Consequently they foraged in a far more varied suite of
ocean habitats than did the Amsterdam Yellow- nosed Albatrosses.
***
If certain sea areas offer good feeding prospects and others slimmer
pickings, an obvious, if overly simple, question arises: why don’t all
birds focus their attentions on the prime areas? There are several partial
answers but, even when combined, I wonder whether they provide a
complete answer.
In Chapter 7, the idea of the ideal free distribution was pondered. If
there are several ways of making a living, a few individuals may advan-
tageously adopt the best. But, if increasing numbers follow that life-
style, its profitability may drop; there are too many birds clamorously
squabbling over the same fish shoal. It becomes more profitable to seek
out another feeding area that is being visited by few other birds. In this
way, birds may become spread out over various feeding areas so that the
birds in each area fare equally well.
Potentially contributing to spatial segregation is the age of the bird.
Younger birds may be less adept at feeding than their elders and betters.
Better to keep out of their way.* Leading to the same outcome, a segre-
gation of feeding areas of immature and older birds, is the fact that, at
least during the breeding season, adults have to visit the colony more or
less regularly to attend the egg or chick, whilst immatures without such
responsibilities are relatively footloose and fancy- free. They may wander
further afield. The two explanations, relative inexperience and freedom
from ties to the colony, are not exclusive: both probably contribute to
segregation of younger and older birds at sea.
In Chapter 3, I described how Annette Fayet discovered that, during
the breeding season, Manx Shearwaters of different ages from Skomer
Island travelled to different sea areas to feed.^19 Importantly the study
- (^) Chapter 3 covered the peregrinations of immature birds. One of the outcomes of these wan-
derings will be a reduction in the interactions between immature and older birds, and reduced
competition for food between the two groups.