The Greenland White-fronted Goose Anser albifrons flavirostris

social system has traditionally regulated recruitment
into the reproductive classes in the Greenland
White-fronted Goose population, but it is
tempting to speculate this was and remains the
case. The population is characterised by unusually
prolonged parent-offspring relationships
(25% were still associated with one parent in their
seventh winters, MS 11), even compared to other
races of White-fronted Geese (Ely 1993). Yet the
production of young per successfully breeding
female (measured by family brood size on the
wintering grounds) is unusually high compared
to most other goose populations, consistent with
the idea that only the highest quality pairs breed
in any one year. These features are consistent with
a social system that enables successful pairs to
maintain high social status through persistent
association of earlier offspring, which seem likely
to remain with their extended families because
of the high relative cost of pairing and losing such
status. Reproduction in the population as a whole
therefore involves a relatively low proportion of
the potentially reproductively active individuals
- generally only those of high quality (see Figure
9.1 and 9.2 above).
Under legislative protection from shooting on the
winter quarters, the population has shown an
increase consistent with constant adult survival
and observed breeding success rates. If some density
dependent function were involved, whereby
the overall number of opportunities to nest in any
one year were limited to the same number every
year, it might be expected that, above this threshold
level, entry into the breeding class would be
severely limited. There is now some emerging
evidence to suggest that such a limit exists for
the Greenland White-fronted Goose. Amongst
those wintering at Wexford and Islay (some 60%
of the total population), the number of successfully
breeding pairs returning with young steadily
increased during the 1970s, although production
in any one year varied with summer temperature
in Greenland (Figure 9.3). Since protection
from hunting, the absolute number of successful
breeders has been stable at c.1,000 pairs
in years when cold summer conditions have not
limited successful breeding (Figure 9.3). There
does seem therefore to be a current limit to the
number of pairs that can breed successfully
amongst birds using these two wintering resorts
(chapter 6). This is manifest amongst the marked
population in falling recruitment levels amongst
cohorts hatched since 1984, partly a result of delayed
age of first breeding amongst this sample
Number of successful breeding pairs at
Islay and Wexford combined
1200
1000
800
600
400
200
mild springs
cool springs
0
1965 1970 1975 1980 1985 1990 1995 2000
Figure 9.3. Total number of successfully breeding pairs
(i.e. parents returning with at least one young) in autumn
from Islay and Wexford combined. Open symbols
are years with cooler than average June temperature
in West Greenland, solid symbols warmer than
average (based on data from Zöckler & Lysenko (2000).
Note the apparent constant maximum number of successful
breeding pairs since protection (arrow) in seasons
of above average summers.
but also declining brood size amongst those that
breed (chapter 6).
The demographic data support the idea that there
is an apparent current 'ceiling' to reproductive
output in this population, but it is far from clear
how this limitation is exercised. There might be a
limit to the extent of breeding habitat or number
of nest sites, but these seem highly unlikely, given
the wide extent of available habitat (chapter 6).
Furthermore, the limit could be to brood rearing
nursery habitat, or to the post fledging survival
of young. Both of these factors also seem highly
unlikely, given that a density dependent mechanism
would tend to reduce brood size (for example,
as a result of losses of smallest goslings Owen
& Black 1989), rather than result in a loss of entire
broods from the population. In the Greenland
Whitefront, a characteristically low proportion of
successful breeders return with unusually large
families compared to other geese populations.
Hence, it would therefore appear that relatively
few pairs attempt to breed in any one year, and
amongst those pairs which do, the majority breed
successfully, in terms of raising large numbers of
young per family that survive to reach the wintering
grounds. As discussed above, this could
be the result of density-dependent limitation in
access to nutrient acquisition on the wintering
grounds, the Iceland spring staging areas, in
Greenland during pre-nesting feeding or a combination
of all three. Since the extended family
relationships persist on the wintering, spring stag-
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