What ecological role do mergansers sometimes fulfill due to their feeding habits?
Answer
They serve as excellent indicators of water quality.
Because mergansers rely on visually locating their slippery prey, they thrive best in environments where water visibility is high, thus making them effective indicators of healthy aquatic ecosystems.

Related Questions
Why are mergansers often nicknamed "sawbills"?How do mergansers propel themselves underwater while pursuing prey?What color is the head of a female Common Merganser?Which sex of the Common Merganser is the primary vocalizer?What ecological role do mergansers sometimes fulfill due to their feeding habits?What physical adaptation makes mergansers somewhat clumsy when walking on land?What specific detail must an observer note to differentiate a female Common Merganser from other species?Where do Common Mergansers typically choose to build their nests?What iridescent quality can be revealed on the male Common Merganser's head in bright sunlight?Which type of water body do Common Mergansers utilize in addition to large freshwater lakes and rivers?