Black swan event

 The definition of which is an unpredictable, rare, (and high-impact) occurrence that defies conventional forecasting - which probably doesn't really describe another back swan sighting, this time in Emsworth, but acknowledging that they are quite rare birds.

 Of course the bird may have just moved down the coast a few miles from Hamble to Emsworth where a local man Gordon has been feeding and leading Swan welfare activities.