A bill built for one thing, and one thing only
The Indian Skimmer (Rynchops albicollis) has a lower mandible that is measurably longer than its upper one, a trait so rare among birds globally that only three skimmer species in the world share it. It flies low over calm water, lower jaw slicing the surface, snapping shut the instant it touches a fish. This is not a generalist. Every part of its anatomy is committed to large, slow-moving rivers with clear shallows and open sandbars. When those rivers change, the bird has nowhere to adapt to.
