Fig. 1. (A) Continuous line: example of beak movement in a Humboldt penguin associated with approximately 7 breaths. The dotted line shows the increase and decrease of the air in the respiratory system over the course of the breath cycle. (B) Example of the beak movement of a Humboldt Penguin associated with 2.5 breaths. The line shows a peak and a trough translated (arrows) onto a pure sine wave (above) for comparison.