The Greenland White-fronted Goose Anser albifrons flavirostris

other races, but density dependent processes restrict
the ability of young inexperienced birds to
nest and incubate successfully? The increase in
the age of first breeding in very recent years has
contributed to the general decline in recruitment
amongst marked cohorts of known age birds since
1984. Observations on the wintering grounds
show that Greenland White-fronted Geese have
a rigid social dominance hierarchy, so that a major
determinant of an individuals’ access to best
feeding opportunities is the size of group with
which it is associated (Boyd 1953). A young pair,
abandoning the ties with parent-sibling groups
(which may number up to 15 individuals in size)
falls from a high-ranking group to a two-member
group, with all the consequences for access to
food and other resources that this behavioural
change entails. Hence, the first step towards a
reproductive attempt, that of obtaining a mate
and accumulating appropriate stores for investment
in successful reproduction, may carry a very
heavy initial cost. The benefits of membership of
large extended family units are found on the staging
areas as well. In spring, family groupings
maintained on the wintering grounds are perpetuated
at staging areas in Iceland (MS27).
Hence, at a number of stages in the life cycle, the
decision to leave a family, form a pair and invest
in a reproductive attempt may result in loss of
access to best feeding opportunities at a number
of points in the non-breeding periods of the annual
cycle.
On the breeding areas, too, there may be advantages
to existing parents of extended parent-offspring
relationships. In another race of Whitefronted
Geese, central Canadian arctic frontalis
young of previous years have been seen contribute
to pre-nesting feeding alertness of potentially
breeding pairs, and to remain in the vicinity of
nest sites to assist with nest defence (MS12). In
the absence of such 'helpers', new breeders may
risk higher predation rates and hence impaired
reproductive output for reasons other than experience.
In terms of securing resources for the annual
cycle of overwinter survival, spring migration
and investment in reproduction, there would
seem every advantage to remain with a group of
kin, even for part of the year. However, as far as
we know, this does not happen. Young birds leave
family groups on pairing to embark upon a reproductive
attempt as a lone pair. Hence, the low
reproductive output of this population may in
part relate to the behavioural consequences of
flock structure, which creates a disincentive for
54
young birds to leave a large social group of related
birds and attempt to 'set up home alone' as
a lone pair. In other words, the high resource cost
of leaving a family grouping favours delayed
pairing relative to other races of the same species.
Mature breeding pairs have the benefit of
experience and the presence of associated offspring
“helpers” from previous seasons. In contrast,
inexperienced first time breeders (lacking
associates) are likely to fail in the early stages of
their reproductive lives. Furthermore, there could
be some advantages to offspring in extended association
with parents in gaining knowledge
about successful reproductive techniques. This is
supported by the fact that brood size increases
with age at first breeding (MS8).
Given the continued increase in the numbers of
geese wintering on Islay and the decline at Wexford,
it is tempting to speculate that these differences
in patterns of abundance are related to factors
affecting the birds on the wintering areas. The
extent of favoured feeding habitat has been reduced
at Wexford in recent years, which could
potentially affect the condition of departing birds
and hence their reproductive success. There have
been great changes in the extent and quality of
grassland most favoured by the geese at Wexford
Slobs in the last 14 years, and this has been reflected
in the habitat use by collared geese at the
site (Figure 6.9). Geese there increasingly use fodder
beet provided as a sacrificial crop for longer
Percentage habitat use
100
90
80
70
60
50
40
30
20
10
0
1984
1986
1988
1990
Year
1992
1994
1996
1998
Reseeded grass
Stubble
Root crops
Winter cereal
Beans
Figure 6.9. Proportion of different major habitat types
used by wintering Greenland White-fronted Geese
wintering at Wexford Slobs during the period 1984/
85-1998/99. Data presented are based upon observations
of collared birds only, since habitat type is recorded
for every single field observation of these birds.
There has been a significant decline in the use of grass
and significant increase in the use of root crops (principally
beet increasingly grown as a sacrificial crop for
goose use at the site) 10 .