An ROC Ornithological Society survey has shown that wild geese and ducks congregate along the middle reaches of the Hsiukuluan River because the more densely inhabited lower reaches are frequented by boaters, which explains why they are most often sighted around Yuli.
根據中華民國野鳥學會調查，秀姑巒溪下游是泛舟地點，人煙較多，因此雁鴨集中在中游，這是玉里農民較易見到雁鴨的理由。