The Greenland White-fronted Goose Anser albifrons flavirostris

ing and (to a lesser known extent) pre-breeding
areas, it seems likely that a brood female with attendant
offspring from previous years obtains
considerable advantages for nutrient acquisition
during all three phases of the prelude to breeding.
Furthermore, the association of offspring
from previous years could potentially enhance nest
defence and protection of subsequent hatched
young. In contrast, lone pairs face considerable
disadvantages owing to their low social status,
which denies them access to the best feeding opportunities.
They must increase food intake rates
to compensate for loss of access to richest food
patches by consuming higher quantities of lower
quality foods to meet threshold levels of stores
needed to attempt reproduction. Even after laying
a clutch, the lone pair lacks kin associates for
nest defence from predators.
It therefore seems most likely that there is a limit
to individuals entering the breeding class and this
limitation is likely to be condition based. It is already
known that pre-nesting feeding areas are
spatially limited in spring and patterns of snowmelt
could impose further limits on food availability
(see Glahder 1999). Hence, pre-nesting
spring food availability is likely to specifically
limit resources available to potential brood females.
Only those individuals most efficient at
nutrient accumulation in the period up to and immediately
after arrival in Greenland can achieve
the necessary stores for successful reproduction.
9.2The impact of hunting mortality
In the absence of histories of individually marked
birds from the years when hunting occurred in
all seasons, it is impossible to determine the true
effects of winter hunting mortality on Greenland
White-fronted Geese. The comparison between
Haldane estimates of survival before and after
protection suggests hunting was additive. The
simple modelling exercise included here (chapter
8) gives some support to the hypothesis that
completely additive hunting mortality at Wexford
would explain the period of stable numbers during
1969-1982, and the observed rate of increase
after protection. However, in the two years when
hunting was permitted on the Wexford Slobs since
1982, there was no convincing difference in annual
adult or juvenile survival based on resightings
of individually marked birds.
However, the unusually high mortality in one
78
year (1989) which resulted in 75% mortality
amongst young and reduced adult survival demonstrates
the sensitivity of the population to such
occasional stochastic events, and their impact on
subsequent population trends. As previously
demonstrated, the population is highly sensitive
to small changes in annual adult survival rates
(Pettifor et al. 1999), and therefore, it is not surprising
that the removal of winter hunting had
an immediate effect on population trajectory.
Given this direct impact of changes in survival
rate on change in population size, it does appear
that protection from hunting was the cause of the
increase in numbers in the population after 1982.
The site-safeguard programmes of the last 20
years have only contributed in so far as protection
of regularly used roost sites and other protected
areas have guaranteed their perpetuation.
An interesting feature of the relationship shown
in Figure 9.3 is the apparent 'jump' in the number
of successful pairs which returned to Islay and
Wexford in warm summers following protection
from hunting on the wintering grounds. There
seem some grounds for believing that the levels
of recruitment amongst these wintering elements
of the population increased rapidly to the current
(apparently limited) level immediately following
cessation of hunting. In the absence of resighting
histories of individually marked birds before and
after protection, it is impossible to explain this
phenomenon in terms of individual behaviour.
Nevertheless, it is interesting to speculate as to
whether hunting has an effect on reproductive
success in the population as well as a direct effect
on adult annual survival. Such a relationship
could be the result of the effects of wildfowling
disturbance to geese, known to affect breeding
success in some populations (Madsen 1995).
However, it is also clear from observations on the
wintering grounds that extended families tend to
fly in small unattached groups, whilst non-breeding
elements of the population aggregate into
large flocks (unpublished data). Hence, although
families form a very small proportion of the overall
population, their potential frequency of encounter
by a hunter is disproportionately high.
Observations of behaviour of wildfowlers hunting
Pink-footed Geese in west Jutland, Denmark
have shown that hunters tend to shoot at individual
goose flocks as these are encountered. In
that study, family groups were more likely to be
shot at than large flocks of geese not because of
their numerical abundance, but simply because
of their greater frequency of encounter with hunt-