I saw this rather elegant scene in St Andrews earlier this month. A pair of adult swans preening themselves by the Kinness Burn just upstream from the harbour. In the background a pair of juvenile swans gently wend their way back to their parents before finally joining them in preening. Swans have a preen gland at the base of the tail. The oil that’s produced there is thought to help waterproof and strengthen the feathers, and moisturise the bird’s bill, legs, and feet. Preening also helps to remove debris from the feathers and straighten them.