Cardiff in making iron and later steel, brought to the sea by packhorse from Merthyr Tydfil. This was first achieved by the construction of a long canal from Merthyr (510 feet above sea-level) to the Taff Estuary at Cardiff. Eventually the Taff Vale Railway replaced the canal barges and massive marshalling yards sprang up as new docks were developed in Cardiff – all prompted by the soaring worldwide demand for coal from the South Wales valleys. At its peak, Cardiff's port area, known as Tiger Bay, became the busiest port in the world and – for some time – the world's
Cardiff Bay Barrage Wales Rally GB. According to two studies published in 2006, the loss of intertidal mudflats has resulted in the numbers and diversity of the birds using Cardiff Bay greatly reducing. Almost all of the common shelduck and shorebirds that used the bay when mud was exposed no longer feed there. Initially these birds used nearby sites to feed, but in most cases, this behaviour was not sustained, and the birds were unable to settle elsewhere. Common redshanks displaced from Cardiff Bay settled at the nearby Rhymney estuary, but they exhibited lower body weight, and their annual survival rate declined from