59. Current status of tundra cranes species populations in Yakutia

Abstract

Just two from four breeding species of cranes in Yakutia, Siberian Crane Grus leucogeranus and Sandhill crane Grus canadensis canadensis , are found in the most northern areas of the region, inhabiting the subarctic tundra of the lowland between rivers Yana and Kolyma. Siberian crane is represented by the eastern population in the region. This crane winters in China (Yangtze River downstream basin) and appears to be a typical species of the Siberian fauna and endangered bird of the world fauna. Sandhill crane is an expanding species of American fauna with wintering grounds in Texas (USA) and Mexico. This crane is in a process of active distribution in the northeastern Yakutia and related to rare endangered species of the region. Siberian cranes’ increase of the eastern population number has been observed since the late 1990s on the breeding ground, particularly in tundra of the River Indigirka basin (the number of crane pairs increased from 52 to 56 on the model site of 1314 km 2 ) and on the main wintering ground in Poyang Lake Nature Reserve in the southeast of China (it reached 4 thousand individuals), no doubt, was related to the active scientific and conservation work undertaken within the framework of international cooperation, with a reduction of disturbance factors in key areas of habitat. Nevertheless, the current status of the population is still estimated to be alarming. The optimal habitat of Siberian Cranes is lakeside lowlands and wetlands occupied by 21–26% of the breeding range. They are located outside of the regular spring flooding territories and in uneven and mosaic distribution. The birds inhabit mainly areas adjacent to large and medium-sized lakes, occupying no more than 50–60% of the areas suitable for their nesting. The water content increases in the territory because of the destruction and defrosting of tundra soils that leads to a reduction of the most optimum habitat for the population. An average home range size for a reproductive pair, including its breeding and feeding areas, is 7.3–16.5 or 10.6 km 2 . The rate of population growth (reproduction efficiency varies from 4.3–8.7 to 65–83.3%) allows us to assume that the absence of separate generations of birds which did not live to maturity was due to their very low number and natural losses. The front of the bird migration in Yakutia has a quite narrow corridor. This is especially noticeable in the middle Aldan River at fall where up to 50% of the eastern population is reported from the separate observation points. Siberian crane transit stops are much longer in China than in Russia, and the concentrations of birds are more numerous in China. Sandhill cranes continue to distribute in the western region of tundra and increase their numbers. At present, the range of this species almost completely coincides with that of the Siberian crane (approximately 82 km 2 ). The species number has grown tenfold and reached 56 pairs over the past 20 years on the model site in tundra of the River Indigirka basin.