Total body haematocrit iron kinetics and erythrocyte life span in pigeons (Columba livia).

1. The mean pigeon erythrocyte life span was found to be 17-25 days by Cr51-labeled erythrocytes and 21 +/- 3.4 days by iron kinetics. 2. Total red blood cell volume has been calculated by Cr51-labeled erythrocytes while total plasma volume was determined both by a dye method and iron kinetic data. From these results total blood volume and total body haematocrit were found to be 0.090 +/- 0.002 ml/g body wt and 36 +/- 4.3%, respectively. 3. Venous haematocrit, haemoglobin concentration, erythrocyte count, mean corpuscular haemoglobin concentration, plasma iron and red blood cell iron have also been measured. 4. A significant difference between total body and venous haematocrit and a short mean red blood cell life span, due to ageing and to random destruction of erythrocytes were shown. 5. The above observations are compared with analogous available data for human beings and their physiological significance is discussed.