Spring migration duration exceeds that of autumn migration in Far East Asian Greater White-fronted Geese (Anser albifrons)

Background:Migration theory suggests,and some empirical studies show, that in order to compete for the best breeding sites and increase reproductive success,long-distance avian migrants tend to adopt a time minimization strategy during spring migration, resulting in shorter duration spring migration compared to that in autumn.Methods:Using GPS/GSM transmitters,we tracked the full migrations of 11 Greater White-fronted Geese (Anser albifrons) between southeast China and the Russian Arctic,to reveal the migration timing and routes of the East Asian population, and compare the difference in duration between spring and autumn migration of this population.Results:We found that migration in spring (79 ± 12 days) took more than twice as long to cover the same distance as in autumn (35 ±7 days).This difference in migration duration was mainly determined by significantly more time spent in spring (59±16 days) than in autumn (23± 6days) at significantly more stopover sites. Conclusions:We suggest that these geese, thought to be partial capital breeders, spent almost three quarters of total migration time at spring stopover sites to acquire energy stores for ultimate investment in reproduction, although we cannot reject the hypothesis that timing of the spring thaw also contributed to stopover duration.In autumn,they acquired necessary energy stores on the breeding grounds sufficient to reach Northeast China staging areas almost without stop, which reduced stopover times in autumn and resulted in the faster autumn migration than spring.

Coupling the Occurrence of Correlative Plant Species to Predict the Habitat Suitability for Lesser White-fronted Goose (Anser erythropus) under Climate Change: A Case Study in the Middle and Lower Reaches of the Yangtze River

Climate change and human activities influence species biodiversity by altering their habitats. This paper quantitatively analyzed the effects of climate change on a migratory bird. The Lesser White-fronted Goose(LWfG), a species which migrates via the middle and lower reaches of the Yangtze River region, is an herbivorous species of high ecological value. It is an endangered species threatened by climate change and human activities, so comprehensive information about its distribution is required. To assess the effectiveness of conservation of the LWfG under climate change, both climate variables and human activities are often used to predict the potential changes in the distribution and habitat suitability for LWfG. In this work, the current scenario and the Global Circulation Models(GCMs) climate scenarios were used to simulate the future distribution of the species. However, besides climate change and human activities, the spatial pattern of plants surrounding the wetland is also known to be closely related to the distribution of LWfG. Therefore, the distribution model results of six plant species related to LWfG’s diet selection were used as environment variables to reflect the changes of suitable LWfG habitat. These environmental variables significantly improved the model’s performance for LWfG, since the birds were clearly influenced by the plant distribution factors. Meanwhile, the suitable habitat area decreases by 2070 in GCM models under two representative concentration pathways scenarios(RCP2.6 and RCP8.5). More appropriate management and conservation policies should be taken to adapt to future climate change. These adjustments include modifications of the size, shape and use of the conservation area for this species.

Climate change and contrasting plasticity in timing of a two-step migration episode of an Arctic-nesting avian herbivore

Greenland white-fronted geese Anser albifrons flavirostris wintering in Britain and Ireland migrate over the sea for 700-1200 km to stage 3-5 weeks in Iceland in spring, continuing a similar distance over the sea and Greenland Ice Cap to West Greenland breeding grounds. During 1969 to 2012, the geese advanced the mean departure date from Ireland by 15 days, during which time also they attained threshold fat stores earlier as well as departing in fatter condition. Over that period, Iceland spring-staging geese shifted from consuming underground plant storage organs to grazing managed hayfields, which provide fresh grass growth despite sub-zero temperatures, when traditional natural foods are inaccessible in frozen substrates. In 2012 and 2013, geese arrived three weeks earlier to Iceland, in fatter condition and accumulated fat significantly slower than in 1997-1999 and 2007. Although geese accumulated sufficient fat stores earlier in Iceland in 2007, 2012 and 2013, they departed around the same date as in 1997-1999, prolonging spring staging by three weeks. Plasticity in winter departure dates is likely due to improved winter feeding conditions （enabling earlier departure in better condition） and a novel predictable food resource in Iceland. Greenland white-fronted geese attained threshold fat stores in Iceland earlier, but remained rather than departing earlier to Greenland. Despite arriving earlier in Iceland, arrival dates on the breeding areas have not changed since the 1880s, presumably because of relatively constant cool springs and heavy snowfall in West Greenland during recent years [Current Zoology 60 （2）： 233-242, 2014].