The Greenland White-fronted Goose Anser albifrons flavirostris

more direct measures of 'body condition' in determining
factors affecting individual performance.
1.5 The flyway concept as related to
Greenland White-fronted Geese and
the format of this thesis
The study of the Greenland White-fronted Goose
has never been a full time project for any of the
characters involved. In Ireland, the National Parks
& Wildlife Service has made a substantial annual
commitment to research and survey of Greenland
White-fronted Geese since the 1960s, when counts
and age ratio assessments were made at Wexford.
In more recent years, the regular marking of a
sample of individuals captured at Wexford and
substantial effort invested in the resighting of
these individuals has generated an impressive
database of knowledge to support the international
research and survey effort. However, elsewhere,
the work has been carried out on an ad
hoc basis, gathering data for differing purposes
at different stages of the life cycle. The result is
something of a ragbag of information, not always
well inter-linked, and certainly never based upon
a single research plan with well-defined targets
and objectives. The available information is therefore
scattered, and one purpose of this thesis is to
draw together the disparate strands in order to
determine what information is available and identify
the gaps in the existing knowledge.
Much of the reference material relating to Greenland
White-fronted Geese has been gathered in a
recent review and need not be repeated here
(MS24). This forms the background to the thesis,
in the sense that many of the results of studies
are summarised there. Chapter 1 establishes the
setting for the thesis. There follows a review of
taxonomic relationships and the recent history of
the Greenland White-fronted Goose that attempts
to conclude something about the potential limits
to this population (chapter 2). The following chapters
explore the elements of the life cycle where
critical factors may operate with respect to fecundity
or survival. Outside the breeding areas, there
are four periods of the annual life cycle when
Greenland White-fronted Geese must accumulate
stores in anticipation of long migratory flights.
The population stops off in Iceland in spring and
autumn en route to and from Greenland. The geese
must accumulate energy stores enough to travel
to and from Iceland and Greenland. Since spring
acquisition of stores in anticipation of the spring
flight to Iceland, and thence onward to Greenland
will also have consequences for reproduction,
these two events in the annual life cycle have
attracted considerable interest, and have separate
chapters to themselves (chapters 3 and 4).
On arrival in west Greenland after traversing the
Greenland Ice Cap, the geese must again replenish
depleted stores in preparation for the reproductive
period. Geese were once thought to be
largely capital breeders, investing stored nutrients
in clutches and their incubation, although
this view is increasingly challenged (see review
in Meijer & Drent 1999). In the case of the Whitefronted
Goose, it is now well demonstrated that
females indulge in extended periods of pre-nesting
feeding when birds can add substantially to
their store of nutrients in readiness for egg-laying
and incubation (chapter 5). For a population
in which the reproductive success is well below
the average for other populations of the same
species, it is important to explore factors that may
limit recruitment and reproductive output (chapter
6). The period of flight feather moult represents
a potentially critical period in annual cycle,
since birds become flightless for several weeks,
making them more vulnerable to predation and
the depletion of local food resources until they
regain the power of flight. The duration of moult
and the period of pre-migration accumulation of
stores in autumn are key elements in the annual
cycle of the population (chapter 7).
The return flight from Greenland, again stopping
off in Iceland, has been little studied, although
there remains the potential for occasional mass
mortality associated with this migration episode
(as well demonstrated for other goose populations,
e.g. Owen & Black 1989, Boyd & Sigfusson
in press). In comparison with high arctic forms,
late summer and autumn are periods of plenty
for Greenland Whitefronts, when food in Greenland
and Iceland is not especially limiting and
the weather is rarely sufficiently severe to cause
between year variation in adult annual survival.
That said, there remains an autumn hunt of this
population, involving some 2,900-3,200 birds shot
every year in Iceland. This period remains a priority
for future research.
Having reached the overwintering habitat, it is
important that this habitat is sufficient in quantity
and quality to ensure survival. There was
considerable evidence that in the 1950s, habitat
15