Barnacle Geese on Kolguev Island 63
©Wildfowl & Wetlands Trust
Wildfowl
(2013) 63: 56–71
In addition to the colonies formed
around falcon nesting areas, two colonies of
a new type were found in 2011–2012 in the
central part of Kolguev Island. Both of
these colonies (B_1 and B_2 in Fig. 1 and
Table 2) were situated on sedge-moss bogs
formed at the bottoms of dried-out lakes in
areas, where there was no sign of a colony in
2007–2008. Nests were mostly placed on the
tops of peat hummocks protruding from
wet moss mats flooded by spring melt
waters, and neither colony was associated
with any raptors. These two colonies were
highly successful (hatching success 67–80%)
in both seasons and colony size increased
from 49 in 2011 to 76 in 2012 in one of
them, and from 37 to >40 (nests were not
mapped; only counted from a distance in
2012) in the other (Table 2). Indeed, the
hatching success of Barnacle Geese nesting
in the two bog colonies in 2011–2012 (
c.
73% of 162 clutches where breeding success
was monitored were thought to have
produced at least one gosling) was similar to
that of geese associating with Peregrine
Falcons in the same years (75% of 192
monitored clutches hatched;
χ
2
1
= 0.02,
n.s.). The areas available for the two bog
colonies are relatively constant, being
restricted by the outer borders of dry lakes
(0.11 and 0.24 km
2
respectively). At colony
B_1, the nesting density increased from 440
nests/km
2
in 2011 to 680 nests/km
2
in
2012; at colony B_2, however, nesting
density was much lower and did not exceed
200 nests/km
2
, possibly due to the wetter
nature of the habitat with fewer peat
hummocks protruding from the wet moss
bog. Moreover, these two new colonies were
situated in the vicinity of two other falcon-
species. In 2011–2012 not only did all 11
inspected falcon nests (including all nests in
the watershed habitats) have Barnacle
Goose colonies within the falcon protected
area (
c
. 0.075 ± 0.05 km
2
around the falcon
nest,
n
= 12 nests), but the number of
Anser
species nests within the area protected by
falcons had drastically decreased (Table 3).
In 2007, colony F_14 had 18 nests of
Anser
geese species and no Barnacle Goose nests,
in 2008 the first two Barnacle Goose nests
were recorded (along with 13
Anser
goose
nests) and in 2012 we found 16 Barnacle
Goose nests but no
Anser
goose nests in the
area protected by the falcon.
Colony occupancy also became more
consistent over time. In 2006–2008, when
falcon pairs skipped nesting, the Barnacle
Geese abandoned nesting in the absence of
the raptor protection (3 of 6 cases where the
falcons skipped nesting), whereas in
2011–2012, geese continued to nest in all 8
cases where the falcons skipped nesting on
their territories (Table 2). Moreover, we
found no significant difference in breeding
success between Barnacle Goose colonies
nesting in the presence of falcon pairs
(91%) and those nesting without (69%) in
2011 and 2012, though sample sizes were
small (Mann Whitney U test:
W
= 39.0,
n
1 = 5,
n
2 = 6,
P
= 0.12, n.s., Table 2). Two
of these colonies (F_16 and F_23) increased
markedly in size in 2012 and pairs in both
colonies bred very successfully, despite the
falcon pairs skipping nesting in both cases
(Table 2). The opposite was true for another
colony (F_15), which had a larger colony
when the falcon pair was not nesting in 2011
than when they were breeding in 2012
(Table 2).
