The Greenland White-fronted Goose Anser albifrons flavirostris

imagery and searches in helicopters, that snowfree
areas in west Greenland with suitable vegetation
for staging White-fronted Geese were limited
(c.28 important areas, with 8 supporting over
75% of all staging geese). Hence, there may be
another density-dependent mechanism (partly
dependent upon the pattern of thaw in each
spring up the west coast of Greenland) which may
restrict the ability of an individual to recoup its
stores in readiness for investment in reproduction
after the costs of migration from Iceland.
In seasons with a late thaw, geese staging in the
region of 66-69ºN but breeding further north face
two alternatives. After initial refuelling they can
move northwards into (possibly) unknown conditions
or remain further south amongst higher
densities of local breeders. In 1999, the thaw north
of 69ºN was greatly delayed. Geese flying northwards
from staging areas would have encountered
low temperatures and complete snow cover,
resulting in lack of access to food and high thermoregulatory
costs. In such a year, the northern
summering portion of the population would be
expected to breed with much lower success rate
than those in the south, and this was certainly
the case in 1999. The geese wintering at Islay
(thought mainly to nest between 66 and 69ºN)
returned in autumn 1999 with 10.5% young (a
below average production of young) but those
wintering at Wexford (thought to summer largely
north of 69ºN) had the lowest level of production
on record (5.5% young). It could be expected that,
in late springs when snow reduces the availability
of feeding sites throughout west Greenland,
competition for limited resources in the immediate
arrival period between 66-69ºN could potentially
result in a general reduction in breeding
success in the population as a whole. Since nesting
densities are still so low, and breeding habitat
not obviously limited, it seems possible that
spring staging habitat could be a factor restricting
females from achieving breeding condition.
This could be one limit to reproduction that would
operate well before any density threshold is
reached where nesting habitat per se restricts the
number of pairs attempting to nest. It is rare that
cold conditions prevail in the southern part of the
breeding range and not in the north, so a further
prediction may be that, despite highest breeding
densities in the region of 66-69ºN, the effect is
likely to be increasingly manifest amongst the
birds breeding in the north of the range.
5.4 Conclusions and discussion
We still know little about how Greenland Whitefronted
Geese acquire the resources to invest in
reproduction on the nesting grounds after arrival
from Iceland. Much more research is needed to
determine the precise body condition of geese
newly arrived from Iceland and the consequences
of pre-nesting feeding and its contribution to a
successful reproductive outcome. Arrival weights
confirm that geese lose more weight (adult males
c. 550 g and adult females c. 330 g based on arrival
API converted to mass from Glahder 1999)
on the 1,500 km passage from Iceland than over
the same distance to Iceland from Ireland. However,
this difference is in line with prediction given
the need to climb up over 2,800 m to traverse the
Greenland Ice Cap along the trajectory taken by
satellite tagged individuals. There is a clear need
to establish the precise mechanical costs of the
flight over the Ice cap. We know birds congregate
in favoured pre-nesting staging areas to recoup
stores immediately on arrival. During this
time, body mass (as calculated from changes in
abdominal profile indices) increased at a similar
rapid rate to that in Iceland in spring. Female
geese, protected by attendant ganders, were able
to exploit a rich feeding resource in the form of
underground storage organs of plants during
periods of uninterrupted foraging. Male were also
able to increase body mass at a similar rate during
this time due perhaps to daylight extending
to 22 hours. Nest densities are generally low and
nesting habitat apparently unlimited (see chapter
6). It therefore seems more likely that food
supplies available at spring staging areas in the
central part of the breeding range could limit the
accumulation of stores to support reproduction
rather than any resource associated with the nesting
sites themselves. Because it appears that a
substantial proportion of the entire population
stages between 66 and 69º N, given a finite feeding
resource available, increasing goose density
at these staging areas may increasingly limit the
number of geese attaining a level of body condition
sufficient to permit successful breeding. It is
predicted that the northern segment of the breeding
population will not only face delayed timing
of breeding by virtue of their nesting latitude and
increasingly lower summer temperatures predicted
from global climate change, but also the
effects of greater goose densities on the southern
spring staging areas.
45