Fig. 5. Effect of hypotonic and hypertonic saline infusion (75 and 500 mmol l^–1 NaCl, respectively) on the fractional reabsorption of (A) water, (B) sodium and (C) potassium in freshwater (open symbols) and saline-acclimated (filled symbols) mallards Anas platyrhynchos (circles), canvasbacks Aythya valisineria (triangles) and Barrow's goldeneyes Bucephala islandica (squares). The period of 500 mmol l^–1 NaCl infusion was subdivided into two parts: the period prior to secretion (–) and the period of secretion (+). Values are means ± S.E.M. (N=4 ducks per treatment).