Fig. 5. Choice of prey as a function of water turbidity and distance (experiment IV). Each data point is the individual proportion of choices (mean ± s.e.m.; 9 trials per bird per day; N=5 birds) of choosing the prey side. Target distance to Y-junction is given in parentheses; solid triangles, controls (prey in transparent cylindrical boxes). Prey in all tests were Tilapia species, length 9 cm. Broken line indicates critical value for significant choice (0.77).