Fig. 5. Total ventilation, breathing frequency, tidal volume and air convection requirements (total ventilation divided by oxygen consumption rate) during stepwise hypoxia (A) and subsequent normoxic recovery (B) in bar-headed geese (light grey triangles), greylag geese (black squares) and pekin ducks (dark grey circles). ^*Significant difference between bar-headed geese and both greylag geese and pekin ducks.