KOFFIJBERG K, HUSTINGS F , JONG A DE , HORNMAN M & WINDEN E VAN (2011) Recent developments in numbers and distribution of Taiga Bean Goose Anser fabalis in The Netherlands. LIMOSA 84 (3): 117-131.
The status and identification of Taiga Bean Goose have been
subject of debate in the past decades all over Europe. Recent
findings have shed more light on its taxonomic status and
wintering distribution. In The Netherlands, the species traditionally
occurred in larger numbers in cold winters like 1979/1980
and 1984/1985-1986/1987, as a result of influxes from the regular
wintering sites in the Baltic (Figs. 1-2). However, a more recent
increase in numbers since the mid-1990s, apparent in the
monthly goose counts, contrasted with reports of a contraction
of the wintering range and a decline in the total flyway population.
In addition, identification pitfalls arose, partly because
an increasing number of 'black-billed bean geese' were reported
as fabalis too. This prompted us to investigate all fabalis
records in the national goose count database from 1990/1991 onwards.
All observers who had submitted counts of Taiga Bean
Geese were requested to check and comment upon their
records, given the new insights in status and identification.
Only one third of these (33%, N = 2073) were confirmed to be
Taiga Bean Geese. The remaining records were withdrawn or
regarded as uncertain, as further documentation was not available.
Flocks of more then 100 individuals were checked particularly
carefully and were accepted only when convincing
documentation existed. To complete the current assessment of
status and distribution, all observations entered through the
online platform www.waarneming.nl in the last two cold winters
of 2009/2010 (434 records, including duplicates) and
2010/2011 (607 records), were checked on the basis of descriptions
or photographs submitted with the records. For 2009/2010
only 76 observations were confirmed, for 2010/2011 449. Particularly
in the last winter, extra attention was paid to the occurrence
of Taiga Bean Geese.
The corrected trend, derived from the monthly counts, shows
that Taiga Bean Geese numbers dropped after the series of cold
winters in the mid 1980s. During that time on average 17,850
individuals were counted in cold winters (maximum 22,000 in
1986/1987) and 3100 in mild winters (Fig. 1). In the 1990s, seasonal
peak numbers went down to on average 600 birds, further
declining to an average of 200 after 2000. The highest
number recorded after 1986/1987 was 1400 in 1991/1992. This decline
is in line with trapping data from goose catchers, who did
not catch any Taiga Bean Geese after 1986/1987, although the
species is commonly used as live-decoy to attract wild geese
to the catching site. Also sightings of ringed and neck-banded
birds from the Baltic have not occurred since 1989/1990, confirming
the lack of large influxes from the regular wintering
range. Data from the platform www.waarneming.nl in the recent
cold winters in 2009/2010 and 2010/2011 to a large extent
confirm the pattern observed in the goose counts. In 2009/2010,
an estimated 180 individuals were recorded (seasonal maximum
during the monthly counts was 171). Numbers in
2010/2011 were slightly larger, i.e. 300 birds. This number exceeds
the maximum based on the monthly counts (50).
Data from international censuses also show that the species is
currently in decline and winters increasingly in the
north(east)ernmost part of its wintering range. We assume
that this flyway-level decline and shift in wintering sites is the
main cause for the major decrease observed in The Netherlands
after the mid 1980s. The species is still an annual visitor,
but numbers are small and in several winters do not exceed
100 individuals. Given its rare current status, we recommend
that in future years any observation of Taiga Bean Goose should
be given special attention with regard to identification. For this
purpose, we also advise observers to check family status and
flock structure of presumed parties of Taiga Bean Geese, and always
use (and report) a combination of field characters to
achieve a correct identification (Table 1).
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Tundra Bean Goose Anser serrirostris Taiga Bean Goose Anser fabalis
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