Activity budgets of a wintering population of Purple Sandpipers: Vulnerability to sea-level rise and conservation through coastal engineering?

For wader conservation in the Solent, UK, two ongoing changes are of particular concern: the increase in artificial flood-defence infrastructure, and increasing sea levels. This study describes the ecology of a small population of Purple Sandpipers Calidris maritima, which is mostly restricted to ca. 250 m of engineered coastline at Southsea Castle, Portsmouth, UK, for both feeding and roosting. We used behavioural information from a citizen-science dataset to construct an activity budget through the tide cycle for this population and then simulated Purple Sandpiper foraging under a range of sea-level rise scenarios for 2050 and 2100. The simulations indicated that modest sea-level rises of the order predicted for 2050 would reduce foraging time by 45 min on average, and would completely prevent foraging on some days by 2100. These results suggest this small population might be threatened by sea-level rise and we discuss this in light of proposed coastal engineering works at Southsea Castle. We also discuss the potential for mining citizen-science databases to contribute to conservation decision-making.