Swans have represented beauty, romance and elegance for a very long time. Earlier representations of river birds, (such as this Romano-British Nene Valley colour coated ware) may not have captured them in their regal integrity but it does indicate a common fascination with putting them on pots. Whether it’s Emma Bridgewater or Roman pottery imported from Peterborough to Lincolnshire in the 3rd to 4th centuries.
Feature image recreated from Xavier Romero-Frias https://es.m.wikipedia.org/wiki/Archivo:XRF_12days.jpg under CC license