Greater White-fronted Geese Anser Albifrons Research Articles

The changing abundance and distribution of Greater White-fronted Geese Anser albifrons in the Yangtze River floodplain: impacts of recent hydrological changes

SummaryCount data show that wintering Greater White-fronted Goose Anser albifrons numbers in their Chinese stronghold (the Yangtze River catchment) have fallen from about 140,000 in the late 1980s and early 1990s to c.18,000 now, despite increases in the overall flyway population (mostly wintering in South Korea and Japan). Declines have occurred in Jiangxi, but most markedly in Hunan (predominantly at East Dongting Lake) where the decline has been steady since 2003/2004, with few left from 2008/2009 onwards. Numbers have increased substantially in Anhui (predominantly at Shengjin Lake), which now supports more Greater White-fronted Geese than Jiangxi and Hunan combined. The species appears a habitat specialist in China, confined to grazing short-sward recessional Carex sedge meadows. At East Dongting Lake, reductions in Greater White-fronted Geese numbers correlated with declines in availability of suitable sedge swards, caused by earlier water table recession, which in recent years has meant swards were too tall for geese to utilise from their arrival in autumn. The hydrological changes are most probably due to the commissioning of the Three Gorges Dam in mid-2003. At Shengjin Lake, the increases may be due to recent stable first exposure dates and slow water recession rates which favour short Carex swards attractive to geese; high buffalo grazing density at this lake may also assist in maintaining suitable sward heights. These hypotheses require investigation.

Individually tracked geese follow peaks of temperature acceleration during spring migration

Many migratory herbivores seem to follow the flush of plant growth during migration in order to acquire the most nutrient‐rich plants. This has also been hypothesized for arctic‐breeding geese, but so far no test of this so‐called green wave hypothesis has been performed at the individual level. During four years, a total of 30 greater white‐fronted geese Anser albifrons albifrons was tracked using GPS transmitters, of which 13 yielded complete spring migration tracks. From those birds we defined stopover sites and related the date of arrival at each of these stopovers to temperature sum (growing degree days, GDD), snow cover, accumulated photoperiod and latitude. We found that geese arrived at spring stopovers close to the peak in GDD jerk; the ‘jerk’ is the third derivative, or the rate of change in acceleration, and GDD jerk maxima therefore represent the highest acceleration of daily temperature per site. Day of snow melt also correlated well with the observed arrival of the geese. Factors not closely related to onset of spring, i.e. accumulated photoperiod and latitude, yielded poorer fits. A comparison with published data revealed that the GDD jerk occurs 1–2 weeks earlier than the onset of spring derived from NDVI, and probably represents the very start of spring growth. Our data therefore suggest that white‐fronted geese track the front of the green wave in spring.

Seasonal and Sexual Differences in Migration Timing and Fat Deposition in the Greater White-Fronted Goose

Abstract We investigated fat deposition and the timing of departure of Greater White-fronted Goose Anser albifrons at Lake Miyajimanuma, Hokkaido, which is the largest stopover site in northern Japan, focusing on the differences between seasons and between sexes. We assessed the fat mass of neck-banded geese by observing their abdominal profiles. In spring, the variation in departure dates among individuals was smaller than that in arrival dates, and there was a positive correlation between arrival dates and departure dates in the fall. The factors affecting decision-making relating to the timing of departure are assumed to be the time constraints of migration before breeding in the spring and on the duration of stay in the fall. The spring fat increase in females was larger than in the fall, and had a tendency to be larger than in males in the spring, The seasonal and sexual difference in fat mass increase seems to be explained by the requirement of fat for breeding after departing from the stopover site...

Dynamics and ecological consequences of avian influenza virus infection in greater white-fronted geese in their winter staging areas.

Recent outbreaks of highly pathogenic avian influenza (HPAI) in poultry have raised interest in the interplay between avian influenza (AI) viruses and their wild hosts. Studies linking virus ecology to host ecology are still scarce, particularly for non-duck species. Here, we link capture-resighting data of greater white-fronted geese Anser albifrons albifrons with the AI virus infection data collected during capture in The Netherlands in four consecutive winters. We ask what factors are related to AI virus prevalence and whether there are ecological consequences associated with AI virus infection in staging white-fronted geese. Mean seasonal (low pathogenic) AI virus prevalence ranged between 2.5 and 10.7 per cent, among the highest reported values for non-duck species, and occurred in distinct peaks with near-zero prevalence before and after. Throat samples had a 2.4 times higher detection frequency than cloacal samples. AI virus infection was significantly related to age and body mass in some but not other winters. AI virus infection was not related to resighting probability, nor to maximum distance travelled, which was at least 191 km during the short infectious lifespan of an AI virus. Our results suggest that transmission via the respiratory route could be an important transmission route of AI virus in this species. Near-zero prevalence upon arrival on their wintering grounds, in combination with the epidemic nature of AI virus infections in white-fronted geese, suggests that white-fronted geese are not likely to disperse Asian AI viruses from their Siberian breeding grounds to their European wintering areas.

Current Status and Distribution of Greater White-Fronted Goose in Japan

Abstract The numbers of the Greater White-fronted Geese Anser albifrons frontalis were monitored during winters from 2003/2004 to 2006/2007 throughout Japan. The annual average number of geese in Japan increased from 91,000 to 115,000 during these years and the maximum number reached was 138,000 in 2006/2007. Most geese (84%) stayed in northern Miyagi, and residual flocks were observed in other areas during winter. In the largest wintering area for this species in northern Miyagi, the number of geese has increased from 15,000 in 1987/1988 to 111,000 in 2006/2007.

The relationship between abdominal profile index and body condition of Greater White-fronted Geese Anser albifrons

Abdominal profile index (API) is often used as an index of body condition in studies of anatids. However, few studies have statistically tested the relationship between API and body condition. In this study, we investigated the relationship between API and body condition of Greater White-fronted Geese Anser albifrons, taking into account the structural size effect on body condition. It was found that body mass, excluding the structural size effect, has a positive relationship with API. As API explained only 26% of the variance in body condition, we discuss the limitations of the method and the situations in which it can be used effectively.

The relationship between abdominal profile index and body condition of Greater White-fronted Geese Anser albifrons

Abdominal profile index (API) is often used as an index of body condition in studies of anatids. However, few studies have statistically tested the relationship between API and body condition. In this study, we investigated the relationship between API and body condition of Greater White-fronted Geese Anser albifrons, taking into account the structural size effect on body condition. It was found that body mass, excluding the structural size effect, has a positive relationship with API. As API explained only 26% of the variance in body condition, we discuss the limitations of the method and the situations in which it can be used effectively.

Effects of climatic conditions on the northward expansion of the wintering range of the Greater White-fronted Goose in Japan

The Greater White-fronted Goose Anser albifrons has recently begun to winter at Lake Otomonuma (Akita Prefecture), a migratory stop-over site located 180 km northwest of its main wintering site at Lake Izunuma–Uchinuma (Miyagi Prefecture), in northern Honshu, Japan. Data collected over a 17-year period (from 1987/1988 to 2003/2004) have allowed us to analyze factors influencing the large-scale redistribution of this species. The number of geese in Akita increased during November and December, but decreased in January. The number of geese wintering in Akita from November to December was not correlated with the number wintering in Miyagi; therefore, migration from the breeding area or from northern staging sites seems to have caused the population to increase in Akita in December. The population in Akita decreases with low temperatures in January; however, the decrease in Akita was not correlated directly with an increase in Miyagi from December to January as the geese also visit other more southerly areas in addition to Miyagi. In fact, we found no significant correlation between the size of the goose population in Akita and climatic conditions during November and December. Our analysis demonstrated that the use of Akita by Greater White-fronted Goose in winter was attributed to density-independent effects regardless of the population fluctuation in Miyagi from November to December, and to severe weather conditions in January forcing the geese to move from Akita to a southern refuge.

伊豆沼・内沼における越冬期のマガンの採食場所の分布

Distribution of feeding sites of wintering Greater White-fronted Geese Anser albifrons around Lake Izunuma-Uchinuma (roost) was determined by direct observations during winter of 1997, 1998and 1999. The 68.6% of 110feeding flocks were observed in rice fields within 6km from the lake.