Figure 1.

Change in mean energy reserves during a period in which the bird does not see a predator and is not interrupted. The trajectory in reserves for six different initial levels of reserves is shown. In each case, mean reserves tend to the asymptotic level x**. The overall mean energy reserves, averaged over interruption and the appearance of predators, are indicated by the dashed line. β(0)=0.8 and β(z)=0.05 for z≥1. A(z)=0.001 for all z. Other parameters: μ=0.05, ν=0.2, a=3, b₀=0.5, b₁=1, b₂=0.005.