48 Taiga Bean Goose at Sarobetsu, Japan
©Wildfowl & Wetlands Trust
Wildfowl
(2013) 63: 40–55
and 7,594 (2003), 146 and 9,230 (2004), 1,000
and 7,456 (2005), 531 and 6,751 (2006), 2,014
and 6,178 (2007), 4 and 6,837 (2008), 122 and
7,077 (2009), 665 and 7,559 (2010) and 40
and 7,545 (2011). Numbers reached their
autumn peak in late September or in early
October throughout study (Fig. 4a).
The mean peak count of 7,272 birds
represented 80% of the geese wintering
in Japan, suggesting that most of the
population migrates through Sarobetsu.
Zone C alone supported at least 65% (mean
= 5,857 birds, s.e. = 181) of the population
in autumn (Fig. 5a).
Observations of marked individuals
showed that certain Taiga Bean Geese left
Sarobetsu during the course of the season,
but because these departures were not
always associated with decreases in total
numbers of geese in the area, this suggests
associated immigration. For example, a
goose with red collar A5Z was present in
mid September 2002, when the total
number of geese was 4,000, whereas by late
September when numbers had increased to
5,300 A5Z (and, given that geese typically
travel in family groups, presumably also its
associates) had already moved on.
Taiga Bean Goose numbers in spring
Maximum counts during each 10-day
observation period were again used to
indicate the seasonally changing pattern in
numbers in spring (2002–2012), as numbers
varied on a daily basis for the reasons
described under autumn staging (Fig. 4b).
Peak numbers of Taiga Bean Geese at
Sarobetsu during spring migration were
recorded in mid April in seven of 11 years,
and in late April on four occasions. The
maximum spring count was of 2,776 geese
in 2008, and the lowest of the seasonal peak
numbers was 1,486 in 2012, indicating
relatively stable peak counts during the
study period. The mean peak value over 11
springs was 2,048 (s.e. = 140), which alone
represents > 20% of the total Taiga Bean
Geese wintering in Japan and
c
. 30% of the
mean seasonal peak number in autumn. The
difference in mean peak value between
autumn and spring was significant (
U
= 0,
n
1
= 10,
n
2
= 11,
P
< 0.001).
Duration of staging
Duration of the autumn staging period
Each autumn, the first geese were observed
in early September (2–8 September), except
in 2008 when they were first encountered on
30 August. The last birds of the season were
seen each year between late October and
late November (ranging from 27 October
2002 to 28 November 2005). The extreme
duration of goose presence in the Sarobetsu
study area varied from 51–87 days (mean ±
s.e. = 74 ± 3 days) each autumn. In 2002,
when heavy snowfalls abruptly ended the
staging of geese at Sarobetsu, the geese were
present for an exceptionally short period of
51 days. In the other nine years, the length of
stay ranged from 65–87 days (mean = 76 ±
2 days) from early September to mid
November.
Observations of banded geese (13
different individuals; total autumn sightings
n
= 79 from 2002–2009) revealed minimum
lengths of stay in the Sarobetsu study area
which varied considerably from individual
to individual, and from year to year, ranging
from 1–64 days. The first marked geese to
arrive were not necessarily either the first or
