Figure 4. Examples of blood $\mathrm{P}{\text{o}}_{\text{2}}$ (black) and temperature (red) recordings during flight (gray shaded area) in normoxia (venous (A), arterial (C)) and hypoxia (venous (B), arterial (D)) for bird 45.

Flight duration of (A) 3.3 minutes, (B) 4.2 minutes, (C) 5.7 minutes, and (D) 5.5 minutes.