[Characterization of trophic position of red-crowned crane (Grus japonensis) influenced by the food resource exhausting].

The trophic relations of the red-crowned crane species in Zhalong Wetland, northeastern China may change significantly withrapid decrease of biological resources. In this paper, the influence of food resource exhausting on the trophic levels of this vulnerable species was determined by using stable isotope (δ ¹³ C and δ ¹⁵ N) methods. The results indicated that the mass of δ ¹³ C and ¹⁵ N in the red-crowned cranes were in the range of -17.8‰ to -18.5‰ and 6.9‰ to 8.1‰, respectively. The dominant food chain length of large water fowls in the ecosystem of Zhalong Wetland was 3.8±0.2 in average, of which the examined species, i.e., red-crowned cranes were 3.1 in average, with the range of 2.9 to 3.3. The annual fluctuation range of δ ¹⁵ N values in the red-crowned cranes was from 7.4‰ to 8.8‰ (with the gap of approximately 1.4, which was below the threshold 3.4 that was considered as a trophic level significant change in an ecosystem), indicating the trophic level of this vulnerable species did not change significantly with the losses of large area of their habitats and foods. Nevertheless, the rapid decrease of the target species population with the food resource exhausting indicated that the conflict of food demand of the red-crowned cranes versus resource need of local residents should be resolved for better protecting this extinguishable species.