The Greenland White-fronted Goose Anser albifrons flavirostris

study of the behaviour of marked individuals. We
can use capture-mark-recapture programmes to
estimate survival, follow reproduction, measure
rates of individual emigration/immigration from
wintering sites and determine individual life-time
reproductive success and dispersal patterns
which offer insights into how changes at the
population level are manifest. Such information
is vital if we are to understand the changes at
population level and determine how density affects
the individual, in terms of recruitment and
survival probabilities, with respect to individual
quality. Since populations are composed of individuals
of differing quality, it is important to be
able to show how competitive ability, age, experience
and social status of the individual affect
food intake rates, store acquisition and ultimately
fitness measures. Greenland White-fronted Geese
are long lived and may take six or more years to
enter breeding age classes. For this reason, it is
increasingly important to mark a representative
sample of individuals on a regular basis over
many years, to generate resightings of individuals
and contribute to life histories that establish
asymmetry in dispersal, fecundity and survival
with regard to specific behavioural traits. In particular,
it is increasingly important to maintain a
pool of marked birds to form the basis for studies
of differences in nutrient acquisition throughout
the annual cycle. There have been no specific behavioural
or energetic investigations relating to
the effects of social status and age on access to
best quality food patches, peck rate and general
levels of nutrient and energy acquisition. The relatively
large numbers of marked individuals in this
population, together with their extreme site loyalty,
offer exciting possibilities in this respect. It
is not enough to suggest that dominance hierarchies
potentially skew the ability of an individual
to acquire body stores, there needs to be some
direct evidence of how and why this is achieved.
The lack of detailed information relating to geese
from this population wintering away from Wexford
is lamentable. Given the difference in demographic
patterns between Wexford and Islay, it
would be highly desirable to resume a programme
of regular capture-mark-recapture of individuals
on Islay, preferably through a programme
of collar marking in parallel to those at
Wexford. Catching throughout the season at other
sites would generate data on seasonality of mass
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changes at other resorts for comparison with the
pattern from Wexford. We need to learn more
about the habitat use and other factors affecting
numbers at lesser winter resorts, especially those
that give immediate concern for their well being.
At present, we do not know if the declines at such
sites are due to poor survival, low reproductive
success, high emigration, low immigration or a
combination of some or all of these factors. Again,
it is important to establish the causes of these
changes before it is possible to tackle the conservation
challenge through implementation of management
action.
Finally, having identified the key elements that
potentially influence survival rates and fecundity,
it is essential to test these in the field to establish
some level of causation. Is climate change driving
the difference in reproductive output at Wexford
and Islay? Both wintering aggregations are
showing declines in individual female fecundity,
but this is greater at Wexford, where the effect
has been to cause an overall decline in numbers
not attributable to increases in the balance of
emigration/immigration, nor to changes in annual
survival. Is this because of changes in habitat
at Wexford, cooler summers on the more northerly
breeding areas which Wexford birds tend to
use, or a combination of these factors? We need
simultaneous studies of reproductive output from
different parts of the breeding grounds with respect
to local meteorological conditions from a
number of years to establish the trends and patterns
in breeding success. This would provide a
firmer platform for predictions of the effects of
global climate change than is possible at present,
and enable generation of population predictions
for changing scenarios as global climate models
improve. We also need to understand how density
dependence is manifest through dominance
hierarchies – what are the real costs and benefits
to an individual (e.g. in terms of fat or protein
accumulation rates) of being part of a large group,
or situated at the bottom of the league of social
status? We need to be able to quantify these relative
costs and benefits before we can be in a position
to understand the function of such status and
the strength of its effect in terms of fitness consequences
for individuals. Only by understanding
the behaviour of the individual will we be in a
position to predict the future behaviour of the
entire population.