68 Barnacle Geese on Kolguev Island
©Wildfowl & Wetlands Trust
Wildfowl
(2013) 63: 56–71
nesting habitats, used by Barnacle Geese
only after the population has reached a
certain level, as these habitats are readily
accessed by foxes. These nesting habitats
were never mentioned as being exploited by
Barnacle Geese at their primary breeding
sites on Novaya Zemlya and Vaigach Island
(Syroechkovsky 1995). That these habitats
are now being used in central Kolguev
Island, coupled with high nesting success
both at these and at falcon-associated
colonies (even when the falcons skipped
breeding), might indicate that the inland-
breeding Barnacle Geese on the Upper
Peschanka River have now reached the stage
when they are not as dependant on falcons
for successful breeding as in 2006–2008,
when all cases of successful breeding in the
central part of the island were strongly
associated with falcons. It is also worth
noting that these two new colonies were not
only situated close to each other (there were
only 3 km between them), but they were also
rather close (0.6 and 2 km respectively) to
two large successful falcon-associated
colonies, together comprising
c
. 400 nests (in
four groups), with at least ten solitary nests
spread out between them, thus providing
an opportunity for the rapid growth and
merging of these groups following
increased hatching success in 2011–2012
(Fig. 2, Table 2). The entire upper Peschanka
River area is likely to support further
growth of Barnacle Goose colonies, with
considerable potential for the establishment
of large colonies through a process similar
to that recorded for the Peschanka River
delta colony in the 1990s.
The substantial increase in Barnacle Goose
numbers in central Kolguev Island between
early June and July–August, due to the
westward movements of broods and flocks
of non-breeders from the Peschanka River
delta, has not been mentioned in any earlier
studies (made in the 1980s and 1990s) of
geese on the island. The growth in Barnacle
Goose numbers in the central part of
Kolguev over the last decade may have
considerable consequences for the island’s
ecosystem as their brood-rearing habitats
largely overlap with those of the White-
fronted Geese, although Bean Goose brood-
rearing habitats are more separate
(Kondratyev
et al.
2012). Elsewhere where
Barnacle Goose numbers have expanded and
come into close contact with White-fronted
Geese, there have been indications of a shift
in distribution of the latter, possibly as a
result of competition for food (Zimin
et al.
2007; Kruckenberg & Kowalik 2008). If
Barnacle Goose numbers increase further,
this will likely lead to elevated competitive
interactions between the two species. As the
preferred nesting habitats of Barnacle Geese
and the two
Anser
goose species on Kolguev
differ slightly (Kondratyev
et al
. 2012), there
has been little evidence to date of serious
adverse effects of the growing Barnacle
Goose population on the
Anser
geese at the
nesting stage. However, we have some local
observations, such as the expulsion of
Anser
species from areas around some falcon nests,
and slightly lower clutch size amongst
Anser
pairs breeding
c
. 500 m from the main
Barnacle Goose colony in the Peschanka
River delta (Kondratyev
et al.
2012) that
suggest some limited effects. The most
serious competitive interactions between the
Barnacle Goose and the
Anser
geese can be
expected during the post-hatching period,
