Attracting Terns to Mew Island
BTO is supporting Natural Copeland in a bid to restore Mew Island, one of the Copeland group of islands, to it its past condition when it was a major site for breeding terns – Sandwich, Common, Arctic and Roseate.
The history of Mew Island and Lighthouse Island, as a major tern breeding location was documented in 1941 (Williamson et al 1941) when a team of four ornithologists made a brief visit to the islands. They were able to record breeding Sandwich, Common, Arctic and Roseate Terns totalling 17,600 birds – 12,400 on Mew, 5000 on Lighthouse, and just 200 on Big Copeland. Roseate Terns were restricted to Mew Island where 243 pairs were counted – this was considered a minimum number.
By the time the Observatory was established in 1954 it was evident that the terns had greatly reduced in numbers. In these early years of the Observatory the annual reports do not give a clear indication of tern numbers on both Lighthouse Island and Mew Island but the 1954 report says that the Common Tern colony was “almost wiped out by predators” and that Arctic Terns were “completely wiped out”. It says that 3 pairs of Roseate Terns nested in the Common Tern colony (it is unclear if this is just on Lighthouse Island or if it includes Mew).
By 1956 the CBO report includes the following: “The terns, both on John’s [Lighthouse] and Mew Island, had a poor season. The Roseates possibly faring better than the others. In mid-May there must have been at least 100 nests of Common and Arctic on the west slopes of John’s Island, yet we doubt if one bird reached the free-flying state. We have plenty of evidence for the conviction that the terns will continue to decrease so long as we tolerate such large gull colonies, ie approximately 900 pairs of Herring Gulls and probably at least as many Black-headed on Mew Island”.
The 1959 report provides a clear survey of breeding terns on both islands. On Lighthouse Island there were 114 pairs of Common Terns. On Mew Island there were 627 pairs of Common and Arctic combined, and just 4 pairs of Roseate. No Sandwich Terns were noted on either island. The report says that, though there were fewer birds than the previous year, they were more successful in fledging young. Nevertheless this total represents a minimum of a 93% drop in population since the survey of 1941.
By 1964 there were no terns nesting on Lighthouse, and just 20 pairs of Common on Mew, with no Roseates. By 1966 there were no records of terns breeding on either Lighthouse or Mew.
In late May 2012 we deployed decoy terns (they look like rather tarted-up Common!) plus solar powered acoustic attraction systems on Mew Island. These proved to be extraordinarily effective, when in late June, the colony of Arctic Terns deserted their breeding site on Big Copeland. Within a week they had re-laid on Mew and Lighthouse Islands (mostly the latter), and subsequently had their most successful breeding season in 7 years – up to 300 young terns fledged.
Decoys, acoustic attraction systems, Roseate Tern nest boxes and tern terraces will be deployed in March and April 2013, with the hope of attracting terns from the start of the season – rather than waiting until they desert from somewhere else. We are keeping our fingers crossed.
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