We have a breeding colony of common terns (Sterna hirundo) here at Saltholme. Islands were created and covered with cockle shell when the site was first developed. The terns create shallow scrapes in the cockle to lay their eggs in.
A common tern on the Tees
Over the last couple of years black-headed gulls (Chroicocephalus ridibundus) have started using the islands as well and the two species share the islands nesting amongst each other. This creates one or two problems for the terns though; it means less space on the island for tern nests and it leads to predation of tern chicks. Not the most desirable outcome. You see, because the gulls settle on nests earlier than the terns, many are on eggs before the terns even arrive back to Saltholme, then, when the tern chicks finally hatch, the gull chicks have grown to such a considerable size that a young tern chick becomes a tasty, bite-sized morsel.
Unfortunately the outcome is not totally avoidable but to combat some of this loss in tern productivity we have introduced floating rafts of cockle shell. These tern rafts simulate the conditions required for the terns to nest but with the added bonus that we decide when they are available. We take them in at the end of summer to protect them from the winter winds we experience here and only put them out when the terns arrive back and importantly when most of the gulls have already settled. The idea being this prime tern habitat should be gull free and also predation free.
Teesmouth bird club generously provided three such rafts last year but unfortunately they didn't do as well as we had hoped. We don't think the terns quite had enough space so we decided to put the three together - three become one.
The front raft was three separate rafts last year.
We had to remove four of the side panels before bolting the rafts back together in order to create one single open space. We did this in the glorious sunshine that we have been experiencing this week with the help of our trusty volunteer work party, without which we simply wouldn't achieve half of what we do. We look forward to seeing the results of our efforts as common terns should shortly be arriving in good numbers.