The Greenland White-fronted Goose Anser albifrons flavirostris

Summary
The Greenland White-fronted Goose Anser albifrons
flavirostris is the most morphologically distinct
sub-species of the circumpolar Whitefronted
Goose Anser albifrons. The population
breeds in West Greenland and migrates through
Iceland to winter in Britain and Ireland. After a
period of population decline from the 1950s to
the 1970s, protective legislation enacted on the
wintering grounds in the early 1980s removed
winter hunting as a source of mortality and
population size doubled to the present level of
30-35,000, although numbers have fluctuated in
very recent years. Declines and extinctions at
some wintering resorts continue, despite the
nature conservation objective of maintaining the
current geographical range of the population.
Most research effort has concentrated at the two
most important wintering sites, Wexford Slobs
in southeast Ireland and the island of Islay off
southwest Scotland. These two resorts have supported
some 60% of the total population in recent
years. Irish wintering geese tend to stage in
western Iceland and breed in the north of the
range in Greenland, whilst Scottish birds tend
to use the southern lowlands of Iceland and
breed further south.
Greenland White-fronted Geese habitually feed
throughout the annual life cycle on the lower stem
of the common cotton grass Eriophorum angustifolium,
which they extract from soft substrates in
peatland ecosystems. The restricted extent of patterned
boglands (which formed the traditional
winter habitat) would undoubtedly have constrained
population size, even in a landscape
unchanged by Man’s activities. Exploitation of
this highly specific food in a restricted habitat is
also likely to have shaped its highly site-faithful
habit and influenced the evolution of the unusually
prolonged parent-offspring relationships
which distinguishes this population from most
other geese. During the last 60 years, the race has
increasingly shifted from feeding on natural vegetation
habitats to intensively managed agricultural
grasslands, which in some areas has brought
the population into conflict with agriculture. Despite
this change in habitat use, there has been no
range expansion, since new feeding traditions
continue to be associated with use of long established
night time roost sites.
Consistent with providing advice to support the
most effective conservation management for the
population, the broad aim of the analysis presented
here is to begin to identify factors that could potentially
limit this population or regulate the rate
of change in its numbers. Given that geese are such
social animals, it is especially interesting to examine
how individual behaviour could influence survival
and reproduction, and how this scales up to
changes in the overall population.
This thesis therefore examines the annual life cycle
of the Greenland White-fronted Goose, concentrating
on periods of nutritional and energetic
need (e.g. migration, reproduction and wing
feather moult) and the way in which individuals
may balance their short and longer-term budgets.
Body mass and field assessments of fat stores
were used as relative measures of body condition
(taken to represent the ability of an individual
to meet its present and future needs). Greenland
White-fronted Geese maintained body mass
through mid winter but accumulated mass increasingly
until mid April when they depart for
Iceland. Assuming 80-90% of this accumulation
is fat, departing geese had more than enough fuel
from such energy stores to sustain this spring
flight. The majority of this mass was depleted en
route to Iceland where they staged for another
c.15 days prior to the journey onwards to Greenland.
Here, geese increased body mass by 25-30
grams per day. In total, this is slightly less than
that during December-April but accumulated
over a considerably shorter period. Most Greenland
White-fronted Geese attained these high
rates of mass accumulation on artificially managed
hayfields although they fed also on adjacent
wetlands. The three most common grass species
exploited showed differences in profitability
because of differing leaf densities, growth rates
and nutrient quality - all of which affected food
intake rates and hence the rate of accumulation
of stores by geese. Behavioural dominance is a
major determinant of access to best food resources
in this population. Since individual geese showed
different levels of feeding specialisation on the
three grass species there is the potential for density
effects and social status to influence rates of
nutrient acquisition in Iceland that could affect
their future fitness.
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