Introduction
The Lesser White-fronted Goose Anser erythropus is the smallest
of the so-called “grey” geese of the genus Anser (BirdLife
International 2018). Excluding threatened taxa, grey geese are
traditionally used for subsistence and sport hunting in Eurasia. Arctic
nations especially continue to consider geese as a sustainable source of
fresh meat in spring. However, hunting bans in many European countries,
Republic of Korea and Japan have allowed the various species of grey
geese to become part of agricultural landscapes. In contrast, several
species of grey geese in China prefer to winter on wetlands with
typically low levels of human use, rather than exploiting agricultural
lands that are densely populated by people and their livestock (Denget al. 2018). Since 1994, following rapid population reduction,A. erythropus has been globally list as Vulnerable in the IUCN
Red List (BirdLife International 2018).
Three sub-populations can be distinguished: Fennoscandian, West Asian,
and East Asian, with potential overlap of the breeding grounds between
the West and East Asian sub-populations (Jones et al . 2008).
Aarvak and Oien (2018) note that the Fennoscandian sub-population
appears on the brink of extinction with only 30-35 pairs left, despite
captive breeding and restocking in Finland and Sweden during 1981 –
1999 (Ruokonen et al . 2000; Andersson and Holmqvist 2010). The
number of the West Asian sub-population assessed from counts at
stop-over sites during autumn migration has risen from an estimated
10,000-21,000 in early 2000s (Fox et al . 2010) to 30,000-34,000
in 2015 (Cuthbert and Aarvak 2016) and perhaps as high as 48,580 ± 2,820
in 2017 (Rozenfeld et al . 2019). However, this increase could be
attributed to additional survey efforts for A. erythropus at
previously infrequently or un-visited staging sites in Kazakhstan. The
most recent estimate of the East Asian sub-population is 14,000-19,000
individuals (Jia et al. 2016), accounting for around 25% of the
global A. erythropus population (Jia et al . 2016 and
Rozenfeld et al . 2019). The eastern sub-population of A.
erythropus extends from the Taymyr Peninsula eastward to Chukotka
region (Morozov 1995; Morozov and Syroechkovski -Jr 2002; Lei et
al . 2019a), and in common with other subpopulations, is declining
(BirdLife International, 2018). A range of threats, including habitat
loss and degradation along the migration route and on the wintering
grounds proposed to fragmentation of the formerly continuous breeding
range, have all been identified being responsible for past population
declines (Madsen et al . 1984; Grishanov 2006; Morozov 2006). In
addition, illegal and accidental hunting (i.e. the genuine confusion
with the similar looking Greater White-fronted Goose A.
albifrons , a species that can be hunted legally in Russia) are also
threats to population viability.
Quantitative knowledge of a species spatial distribution is the
cornerstone for its effective conservation. Due to the remoteness and
restricted accessibility, historical observations of the summer range of
the East Asian sub-population are rather scarce (Ruokonen et al .
2004, Morozov 1995; Morozov and Syroechkovski -Jr 2002; Lei et
al . 2019a) Further, there are no systematic surveys covering the
potential range of eastern sub-population of A. erythropus (Fig.
1). Current knowledge on the breeding distribution and habitat
preference of A. erythropus is therefore limited (Egorov and
Okhlopkov 2007, Solovieva and Vartanyan, 2011, Degtyaryev et al.2014). In the last 25 years, ornithologists generally considered that
the East Asian A. erythropus had a patchy breeding distribution,
and the number, position and shape of those areas changed as new
knowledge was acquired from occasional visits to remote sites in East
Siberia as illustrated in Figure 1. Furthermore, an intensive multi-year
survey in the area adjacent to the breeding grounds along the Rauchua
River, West Chukotka, helped locate a number of breeding/molting groups
and separated broods, suggesting that the entire survey area was
populated by A. erythropus (Fig. 2). This suggests that a single
survey in one year, the usual method employed to study distribution of
geese in remote areas of East
Siberia (Egorov and Okhlopkov 2007, Solovyeva and Vartanyan 2011), may
not allow for an effective understanding of the summering distribution,
limiting potential conservation actions for the species.