Creating More islands at Hodbarrow

Blog by  Dave Blackledge - Site Manager, RSPB Cumbria Coast Reserves

RSPB Hodbarrow, on the side of the Duddon Estuary in Cumberland, is the site of an important colony of Sandwich, Little and Common Terns.   They breed on land formerly occupied by one of western Europe’s largest iron mines and began nesting there as the mines closed over 50 years ago.  Predator fencing and warden protection has seen increasing numbers of seabirds breeding on the island created on limestone slag with vital protected space at a premium.  The Life on the Edge project has been helping create more space for our colony to expand.

At the start of the project in 2020, we constructed a new island and carried out work to increase the size of the existing one, giving us around 0.75 ha of extra breeding habitat, protected by anti-predator barrier fence.  Work has continued this winter to further increase the opportunities for breeding seabirds by creating a third island of 0.25ha. and provide a line of marker buoys along our boundary with the neighbouring caravan park to reduce the incidence of boat disturbance near the islands.

Work underway in Feb 2023 to create the new island (left) and the island created in 2021 (centre) by RSPB

The coastal iron mines were enclosed by a seawall at the start of the 20th century to protect works from flooding and thousands of tons of limestone slag from the nearby smelting works were dumped within the wall, providing an ideal substrate for nesting terns when the works were flooded following closure in 1968.  Island creation on site therefore centres around lowering, moving and cutting off areas of the slag bank to create disturbance free areas.
​
This increased space has already begun to prove beneficial to a number of species.  As terns, Black-headed Gulls and wildfowl began to increase behind the initial predator fence deployed in 2016, Little Terns in particular found it difficult to find space away from other species with their tendency to nest in a more dispersed pattern to other species.  The first island created in 2020/21 has attracted most of the 60 or so pairs of common terns to breed creating space for little terns to expand.  This season we have a peak of 53 pairs of little terns – a record for the site, and young are beginning to hatch at the time of writing.

The new island complete with predator fence March 2023 by Dave Blackledge

​With HPAI hitting some Sandwich Tern colonies hard, we are delighted to have 596 pairs currently hatching young on site – a little down on recent years, but probably expected with a presumably reduced UK population this year.  Creating several islands also has the advantages of reducing the chance of predation – any breach of the predator fence would only allow foxes access to one area of the colony – and separating the colony into areas where interaction and movement will be restricted which may help prevent the spread of HPAI throughout the entire site.
​
Eiders too, have benefitted greatly from the works.  With historical averages of around 5 nests, increased breeding space and predator fencing has increased this to 73 pairs, with several large creches seen escaping over the sea wall to the estuary in recent weeks.  Along with 2 pairs of Arctic Terns, 12 pairs of Oystercatchers, 9 pairs of Lapwings and 4 pairs of Ringed Plover the busy breeding islands are proving a valuable haven for seabirds along the Cumbrian coast.
 

Male Eider duck (RSPB images.com)

Previous blogs on RSPB Hodbarrow
Part 1: NEW ISLANDS FOR SEABIRDS AT HODBARROW
Part 2: DOING A GOOD 'TERN'
Part 3: HODBARROW TERN TRENDS
Part 4: 2022 HODBARROW SITE PREPARATIONS