The Greenland White-fronted Goose Anser albifrons flavirostris

periods in each winter as the extent of suitable
quality grass falls and tillage of former grassland
areas (to produce crops largely unattractive to
White-fronts such as linseed and maize) has increased.
These changes in habitat use may have
had nutritional consequences for the geese, which
affect their propensity to breed, although there is
no clear evidence of this from reduced API scores
at departure in very recent years (see Figure 3.3).
Flocks of Greenland White-fronted Geese wintering
at other sites in the south of the range are also
showing the greatest declines in numbers in contrast
to those in the north (MS14). Perhaps global
climate change, or agricultural changes have in
some way increased grass growth, especially in
spring, in such a way that the timing of the nutritional
early stages of growth no longer coincides
with the pre-migratory fattening period of the
White-fronts. Such arguments seem unlikely to
provide a full explanation for what happens to
birds 3,000 km away, given that the geese have 3
weeks to accumulate stores and reserves very rapidly
in Iceland. Even after arrival in west Greenland,
depending on the conditions encountered
there, geese usually have a further period of 2-3
weeks feeding prior to initiation of nesting there.
Since patterns of winter segregation shows some
relationship to those on the staging and breeding
areas, it is equally, if not more likely that it is factors
operating in Iceland and Greenland that are
in some way restricting nutrient acquisition and
hence recruitment. One major factor likely to affect
geese (assuming a finite and constant food
resource) is the increase in local bird density as a
result of the recent expansion in numbers. Prior
to protection, the birds using Islay and Wexford
combined would have contributed some 6,400
non-breeding birds annually to the population as
a whole. With the increase in overall numbers,
the average number since 1982 has been 13,500
non-breeders. There are consequently more than
double the numbers of geese summering in west
Greenland than in previous years, and to these
must be added the increasing numbers of Canada
Geese colonising from North America. Some
White-fronts show signs of moult migration
northwards within Greenland, and the majority
of the moult migrant Canada Geese were in the
northern part of the breeding range of the Greenland
White-fronted Goose. Hence, it seems likely
that there may be increasing competition for food
resources in the northern part of the range. There,
the thaw has always been later (and therefore
productivity more variable dependent upon
weather). The additional numbers of moult migrant
non-breeders of both species could, however,
have resulted in increased depletion of resources,
perhaps at the cost of the number of successfully
breeding birds in the area. To affect output,
this density dependent effect would have to
operate at pre-breeding feeding sites, either
through direct interference competition for a finite
resource or (in the case of food items taking
more than one year to recover from exploitation)
through a reduction in the overall food stock. Such
an effect would be expected to be most manifest
amongst the Wexford wintering birds, especially
in seasons when the spring thaw was delayed, as
has been increasingly the case in recent years.
Hence, the overall decline in reproductive output
may represent the combined effect of increasing
numbers of geese and the result of the general
cooling of the climate in western Greenland.
This cooling has been occurring since the 1990s
(Rigor et al. 2000) and is predicted by the various
models of climate change to continue.
To distinguish between these two alternative explanations,
we need to follow closely the behaviour
and nutritional status of individual birds at
every stage in their annual cycle. Although
changes in fecundity have been documented,
their proximate and ultimate causes remain obscure.
What is important is that the population
size and reproductive output should continue to
be monitored in such a way that we can continue
to follow the trends in population parameters and
make some predictions about the likely trajectory
of overall population size in the future. In this
respect, it is important to understand factors affecting
annual survival as well as fecundity, a
subject considered in chapter 8.
6.7 Conclusions and discussion
Investment in reproduction in a long-lived animal
represents a trade off between the availability
of current resources, the cost of the reproduction
attempt and the probability of surviving to
breed again in a future year. It seems reasonable
to assume that female condition determines the
level of effort invested in reproduction, up to the
point where the effort threatens her own future
survival. In terms of initial investment, it appears
that given the relatively long period of pre-nesting
feeding in Greenland, clutch size decisions
may be made by Whitefronts on the breeding ar-
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