The Greenland White-fronted Goose Anser albifrons flavirostris

mass at different stages of regrowth of flight feathers
shows no significant decline in the mass of
males or females during the flightless period
(MS17). Average body mass was approximately
2.3 kg for females and 2.6 kg for males, close to
the minimum average for both sexes amongst
captured birds in winter (see chapter 3). This suggests
that most of the geese still retain modest fat
deposits throughout moult and are not approaching
lean body mass at this time (i.e. that they retain
some energetic reserve). The lack of any significant
decline in body mass through the flightless
period also suggests that, amongst the caught
sample, there was no difficulty in obtaining necessary
nutrients (particularly energy requirements
and specific protein/amino acids) at these
sites to sustain them through this period.
This pattern is similar to that found in other arctic
nesting geese (e.g. Lesser Snow Geese and
Brant, Ankney 1979, 1984, sympatric Greenland
moulting Canada Geese MS17), in that geese retain
little or no fat stores accumulated prior to
moult for use during the flightless period. However,
they show no decline in overall body mass
whilst regrowing flight feathers. This is in contrast
to the trends described for Greylag Geese
on Saltholm and in the Netherlands (MS17, van
Eerden et al. 1998), where 500-600 g of fat are apparently
accumulated prior to this period. Why
the difference? One reason could be access to food
supply. In arctic situations, growth in plants is
delayed relative to latitudes further south. Since
the highest quality (particularly protein content)
in above ground green parts of monocotyledonous
plants is associated with the early stages of
growth, it may be that food is simply of better
nutrient quality. However, geese in moult sites
above the Arctic Circle can also forage throughout
the 24 hour period, punctuated by short
pauses to rest, rather than showing a prolonged
roosting period at 'night' (e.g. Barnacle and Pinkfooted
Geese, Madsen & Mortensen 1987, Greenland
White-fronted Geese, Jarrett 1999). The interplay
between nutrient absorption efficiency
and food retention time has been demonstrated
for geese (Prop & Vulink 1992). Hence, it would
be most efficient for a foraging goose to 'eat little
and often', filling the alimentary canal and resting
for short periods to extend the digestive period.
The alternative would be to spend prolonged
periods with lower food retention times (i.e. with
less efficient absorption of nutrients because of
high rates of throughput) and rest for a single
prolonged period at night. That Greenland Whitefronted
Geese change from an essentially diurnal
rhythm at other times during the summer (e.g.
MS1, MS3, Madsen 1981, Stroud 1981b, 1982) to
the continuous feed/rest pattern typical of the
moult supports this argument.
Based on the historical capture data (MS17), it is
tempting therefore to conclude that, given the
ability to feed throughout the 24 hours of daylight,
Greenland White-fronted Geese may be able
to sustain their body weight without depleting
reserves and complete moult without exploiting
body stores. At present, we have no means of assessing
the carrying capacity of habitats used for
moulting by the geese and hence no opportunity
to assess whether the current population is approaching
the limit of moulting habitat available
in west Greenland at the present time. However,
the availability and quality of food resources during
moult is certain to be dependent upon patterns
of thaw, and there is no doubt that the timing
of thaw varies considerably with season. In
1999, when there was deep snow covering all
habitats down to sea level in early June north of
69ºN, the extent of available moulting habitat was
likely to have been much more restricted than in
most years.
It is predicted that the climate in central west
Greenland will become warmer in the very areas
where the greatest densities of geese occur in summer
(Zöckler & Lysenko 2000, MS23). If this
proves to be the case, there may be a severe disruption
to the phenology of thaw, which currently
permits geese to exploit the early growth stages
of different plant species following the sequence
of their release from snow patch areas as a consequence
of aspect and local topography. Locally,
elevated temperatures may enhance plant production.
If climate change results in all habitats
in central west Greenland thawing earlier (especially
at high altitude) the flightless moulting
geese may 'miss' the best periods of above ground
plant production if the geese are unable to modify
their moult schedule. Conversely, the predicted
cooling of summer temperatures in the north of
the range could bring more summers with late
snow lie, decreasing the extent of available moult
habitat for birds using this region, and/or reducing
local quality and quantity of the food supply.
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