**4. Conclusion**

This study involved the establishment of an index using multiple elements, which is in the early phase of development for use in biological monitoring. Of course, a detailed study using the index is necessary in order to increase our understanding of contamination of wildlife with multiple elements. However, interestingly, the survey revealed that a similar index could be obtained, despite the investigation of multiple elements. Further, the difference between the degree of contamination by multiple elements in dabbling ducks and in diving ducks was clarified using this index. These results suggest that an understanding of the equilibrium among elements in the animal body is important for the investigation of contamination by multiple elements.
