A quantitative survey of salt and water excretion

The present series of papers on salt and water excretion in birds offers surveys of the state of the art in the different fields. To complete the picture this introduction considers the quantitative role of the various avenues of salt and ater excretion. First, the fraction of total water lost by evaporation; second, the role of salt glands in the elimination of a salt load in birds with functional salt glands; third, the interaction of kidney and cloaca in birds without functional glands.