New islands for seabirds at hodbarrow

By Dave Blackledge, RSPB Site Manager - Cumbria Coastal Reserves

RSPB Hodbarrow sits on the edge of the Duddon Estuary in south-west Cumbria.  Part of the Morecambe Bay and Duddon Estuary SPA, it was the site of one of Europe’s most productive iron mines in the 19th Century.
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As mining operations ceased in 1968, a mixed colony of Sandwich, common and little terns began to nest on the limestone slag by the lagoon formed on the flooded workings.  This colony is now of international importance and its position behind the sea wall, protecting the site from storms, high tides and future sea level rise mean it is an integral part of western Europe’s tern network.

Sandwich terns by Chris Gomersall (rspb-images.com)

​Introduction of anti-predator fencing in 2016 immediately reversed the fortunes of the colony after a few years of fox predation, with tern numbers increasing rapidly. In 2018, predator disturbance of the Sandwich tern colony at Cemlyn on Anglesey led to a large influx at Hodbarrow with 1950 pairs, around 15% of the UK population breeding here that year. The fox free breeding islands have also benefitted other shorebirds, with black-headed gulls, eider, tufted duck, ringed plover and oystercatcher all benefitting and increasing in number.
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With all this activity concentrated on a single 1.5ha island it became apparent that nesting space was becoming an issue. Little terns in particular, arriving and settling later than many of the other species were being squeezed to the edges of the island, picking sub-optimal nesting sites wherever they were able to find their preferred semi-isolated spot.

Little terns by Graham Goodall (rspb-images.com)

​Life On The Edge is addressing this problem by creating further protected breeding habitat at Hodbarrow. Around 12500 tonnes of limestone slag from the adjacent slag bank will be dug and transported to increase the size of the current breeding island from 1.5 ha to 2 ha, alongside the creation of a second 0.25ha island. 

​A further 130m of fencing to protect the new island will also mean that breaching of defences to one island will not give foxes access to the entire breeding area, giving a further level of protection.

Increasing the size of the current breeding island (c) Dave Blackledge

Cutting off the channel to create the new island (c) Dave Blackledge

The newly created island (c) Dave Blackledge

Other works include scraping of vegetation and scrub from an artificial flood bank left over from the mining operations. The aim is to provide further nesting opportunities for the SPA designated lesser black-backed gulls along with herring gulls and great black-backed gulls. 
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The main habitat works on site have progressed well this winter (while complying with the covid-19 guidance) and we now eagerly await the 2021 breeding season to see how the birds respond to the improved and new islands.