Its spectacular plumage can seem a bit out of place against the dark waters of the Wharfe, but even so, a Kingfisher can be tricky to spot on its fishing perch. Listen out for its high-pitched whistling for a clue as to its whereabouts. It's not just the iridescent blue of its wings and head that is gobsmacking - "an azure jewel burning" - the chestnut of its chest is beautiful, too. Incredibly, this colouring is not due to pigment in the feathers, but to their structure, which scatters blue light.