Pitfalls of surveying breeding geese 95
©Wildfowl & Wetlands Trust
Wildfowl
(2013) 63: 90–104
lake or breeding on the island (
i.e.
those
visible from the bank of the lake), along
with guarding individuals close to the
breeding island (Fig. 3). The first goslings
appeared on 4 April. The number of
goslings counted increased until mid-April
but gradually declined thereafter. The
number of parents observed with broods
showed a similar pattern, with a decline
caused both by a total loss of broods and
adoption of broods by other pairs. Nearly all
adult birds that were not accompanied by a
brood left the lake by the end of April or
beginning of May, including those classified
earlier (from their behaviour) as being non-
breeders. Between mid-May and the
beginning of June, an influx of birds was
observed, that came into the area to moult.
At least part of the moulting flock probably
consisted of unsuccessful breeding birds
from the study site, as indicated by repeated
observations of a neck-banded bird that had
been recorded as a guarding male on the
breeding island. The broods all fledged
in June, and left the area immediately
thereafter. Occasionally, pairs and fledged
young returned to the breeding area in
July. Since the number of fledged young
counted on 10 July was higher than those
regularly observed at Lake Uettelsheim
during the gosling-rearing period (Fig. 3), we
suspect that these flocks also constituted
breeding pairs and offspring from other
sites.
Figure 2.
Numbers of nests and territorial pairs of Greylag Geese and Canada Geese at the three study
sites in 2010–2012. Estimated nests are an estimate of the number of nests in the study area due to
incomplete nest counts. Maximum counted nests are nests where species assignment was not possible
(
i.e
. they may be either Greylag Goose or Canada Goose nests). When no bar is depicted, data are
missing. Uett = Lake Uettelsheim, Toep = Lake Toepper, Six L = Six Lakes Wedau.
0
20
40
60
80
100
2010
2011
2012
2010
2011
2012
2010
2011
2012
2010
2011
2012
2010
2011
2012
2010
2011
2012
Uett
Toep
Six L
Uett
Toep
Six L
Canada goose
Greylag goose
Number of nests / pairs
Estimated nests
Counted nests
Maximum counted nests
Territorial pairs
