There’s a whole lot of moulting going on at the moment in the bird world, as they begin to shed their well-worn breeding plumage. My wife found this distinctive feather on our garden path last week. Under the microscope the underside of the feather (top photo) reveals the beautiful repeated pattern of rows of barbs attached to the central shaft (rachis). At higher magnification (second photo down) you can see the rows of barbules on each barb, each ending in a tiny hook (barbicel). When a bird preens a feather by drawing it through its beak, it’s zipping these rows of hooks on adjacent barbules back together again, to restore the feather’s aerodynamic efficiency. In the bottom two photographs the feather has been flipped over to view the upper surface and reveal a clue to its identity – the blue iridescence in some of the barbules. It belonged to a magpie.