Rat eradication success: Seabird populations soar in Isles of Scilly

An ambitious wildlife restoration project launched in 2013 on the Isles of Scilly has delivered significant conservation gains, with populations of Manx shearwaters reaching record highs more than a decade after invasive rats were eliminated from two key islands.

Brown rats had posed a severe threat to ground-nesting seabirds on St Agnes and Gugh, preying on eggs and chicks during the critical breeding season. The eradication programme, implemented to protect the vulnerable bird population, has maintained the islands' rat-free status since completion.

The results have exceeded expectations. Before the eradication effort, researchers recorded only 22 breeding pairs of Manx shearwaters across the two islands. Latest surveys in 2025 documented 225 apparently occupied breeding sites, representing a tenfold increase in the population.

The Isles of Scilly, located off the coast of Cornwall in southwest England, have become increasingly important as a refuge for seabirds threatened by habitat loss and predation elsewhere. The success of the rat eradication programme demonstrates the effectiveness of targeted invasive species control in restoring breeding populations of threatened seabirds.