River Dee Common Terns - Triumph or Disaster?

Common Tern breeding at Shotton Steelworks. Photo: Barry Barnacal

In 2009 one of the UK’s largest common tern breeding colonies, located by the River Dee at Shotton Steelworks, collapsed. In 2008 there were 750 pairs of terns that produced over 1,000 fledged young. In 2009 there were plenty of adult birds at the start of the breeding season but the birds left after a week or so and produced no young at all.

The effect on the Merseyside Ringing Group (MRG), the organisation that had built up the colony in the first place, was confusion. The group had worked here since 1970, when it installed a wooden raft in one of the Shotton Steelworks’ pools and 12 pairs of common terns nested on it, safe from ground-based predators. The colony had grown steadily to 750 pairs. The wooden raft had been replaced by artificially-created concrete islands built and maintained with the help of the owners of the site (including the present owners Tata Steel), by local birders, by the Dee Wildfowlers and by members of the MRG. This was as successful a conservation project as could be imagined and then, without warning, there were no birds.

After the initial shock the MRG analysed the situation, realised that common terns were relatively long lived birds (a 30 year life span is not unusual) and decided that a single missed breeding season was not important.

2010 arrived and so did the terns but they left again without attempting to breed. Was this the time to panic? Well no, this was the time to plan. The hope had been that the failure to breed was a random event but as this was clearly not the case attempts had to be made to find out what was going on. Government agencies were contacted and a working group set up. Plans were set in motion for surveys to be carried out mainly by the members of the MRG. To study the terns’ behaviour MRG invested in remote cameras that worked in the dark so that 24 hour surveillance could take place.

2011 arrived and the investigation process planned the previous year started. As usual some common terns visited Shotton but none stayed to breed.

In 2012 more survey work was carried out but it was becoming clear that the main reason for the colony’s collapse was a major reduction in the fish stocks in the River Dee.

By 2013 survey work started to show a significant increase in the fish stocks and sure enough the terns arrived and produced young. A great result for the people involved with the colony but one more disaster awaited them.

Anti-predator fences on the tern islands at Shotton.
Photo: Peter Coffey

Foxes managed to find their way to the islands and killed all the chicks. 2013 produced no fledged young. However the evidence from the automatic cameras identified the problem with no room for doubt and another plan was put together to protect the islands from land-based predators. In the winter of 2013/2014 fences were erected around all the islands and we waited to see what the 2014 breeding season would bring.

In 2014 the fish stocks were good and the terns arrived to breed. The anti-predator fences worked and 445 young common terns were fledged. A great result for a lot of creative, conservation work but the MRG continues to monitor the situation with a view to ensuring that this success is consolidated and developed.

John Elliott, Merseyside Ringing Group