Posted by: barn owl | August 10, 2008

China Month 2. Satellite Tracking of Siberian Cranes

ResearchBlogging.org
Siberian Cranes (Grus leucogeranus) are critically endangered birds that breed in northern Russia, and winter in Iran, India, and China. Although the populations that migrate to Iran and India have dwindled to just a handful of individuals, the population that winters in Poyang Lake, in southern China, numbers between 2500 and 3000 cranes. To identify important stopover sites on the migration route for Siberian Cranes, Kanai and colleagues placed satellite transmitters on these birds, captured in their breeding area along the lower Ingirka River. Using the Argos satellite system to monitor the position of marked birds, the researchers tracked 5 cranes over the entire migration distance, and 6 over part of their migration route.

The timing of migration start was mid-September to early October, apparently depending on the date of the first -5 degrees C low temperature. All of the birds traveled south through Aumannyan in eastern Russia, to the Qiqihar-Baicheng area in northeastern China. The next major stop for the Siberian Cranes was the Shuangtaize River delta or the Yellow River delta, with a final destination of Poyang Lake, along the middle part of the Yangtze River. The cranes flew a total migration distance of 5312 kilometers.

crane
Siberian Crane (from Siberian Crane Flyway Connection)

Four areas were identified as the most important stopover sites for migrating Siberian Cranes, as they were used by a large proportion of the birds, and for longer rest periods. Approximately 500 cranes spend an average of 36 days in the Qiqihar-Baicheng area, feeding in wetlands both encompassed by and outside nature reserves. Many of the wetlands in this area are threatened by water overuse for agricultural purposes. In the Shuangtaizi River delta area, the cranes and the wetlands on which they feed and rest are theoretically protected within the Liaoning Shuangtai Hekou Nature Reserve. However, there are oil drilling sites within the reserve, and both disturbance from oil field workers and pollution threaten the Siberian Cranes, as well as the other shorebirds that frequent this delta. The Yellow River delta environment also suffers from oil field-related disturbance and pollution, and from fishing and reed-harvesting by locals.

The wintering grounds at Poyang Lake provide the Siberian Cranes with an important food source, the tubers and leaves of the submerged aquatic plant Vallisneria spiralis. This plant is sensitive to fluctuating turbidity and water levels, and its abundance may be affected by hydrological changes caused by the Three Gorges Dam. Protecting the wetlands at the Poyang wintering grounds, and in the major stopover areas for migrating birds, will be critical tasks required to save the remaining Siberian Cranes.

References:

Kanai, Y. (2002). Migration routes and important resting areas of Siberian cranes (Grus leucogeranus) between northeastern Siberia and China as revealed by satellite tracking. Biological Conservation, 106(3), 339-346. DOI: 10.1016/S0006-3207(01)00259-2

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