Fig. 4

Water transparency (a) and turbidity (b) in relation to abundance (mean number of birds per hourly count; black triangles) and capture success (% = successful captures/total attempts; white circles) of Common Terns in Densu Delta Ramsar Site (n = 12; two quadrats had no observations of terns, wherefore correlations between respectively turbidity and transparency as against capture success applied only n = 10 data points), south-east coastal Ghana. The linear (y = ax + b) regression lines shown are for the significant negative relationship between transparency and abundance (a), and the significant positive relationship between turbidity and abundance (b)