Fig. 2.

Relationships between refuelling time and refuelling conditions and the subsequent annual survival of godwits. a The refuelling time in the Wadden Sea shortened between 1995 and 2015. Apparent annual survival of godwits depended on refuelling time and refuelling rate in the Wadden Sea (b, for females and c, for males) and, therefore, the refuelling rate required to maintain annual survival at the 1995 level has increased substantially (6.6 g d⁻¹ rather than 4.9 g d⁻¹ in males and 9.9 g/d rather than 5.6 g d⁻¹ in females). Godwits partially offset staging time loss by increasing their refuelling rates (d for females and f for males). Refuelling rates correlated with density of adult lugworms (e and g). h Lugworm densities in the Wadden Sea satisfied increased refuelling demands of male but not female godwits