Several haematological parameters such as haemoglobin concentration, haematocrit, erythrocyte number, reticulocyte concentration, plasma iron and total iron binding capacity were determined in 118 urban pigeons of both sexes. No statistically significant sex differences among these parameters were found. In 36 specimens (23 males and 13 females), the plasma iron turnover was determined using 59Fe. The results obtained in this species, expressed per 100 ml-I blood. day-' and Kg-' body weight. day-', were compared with those of turkeys, ducks and chickens calculated from earlier papers. The highest values versus body weight were observed in pigeons.Organ (liver, spleen, tibia, heart, leg muscle, ribs, sternal keel, gonads and blood) distribution of 59Fe intravenous injection was analyzed during a period from 5 min up to 120 days (19 different times) in groups of 4 pigeons. At the 6 h period, the organs retained the highest dose (20 % of total Fe injected), but by the 2nd day period, the radioiron in the blood represented about 98 % of the total injected. A fast iron uptake by the circulatory blood was checked and compared with that of other species (domestic fowl, ducks and turkeys). The reticulocyte count in pigeons normally ranged from 4 to 12 %, which was consistent with these results. A linear decreasing radioactivity in blood, with an inflexion point on the 40th day was observed. An inverse correspondence between blood and liver was found. Content in other organs decreased uniformly with time, except the heart where the iron content was practically constant during the whole time. Ribs and sternal keel are erythropoietic organs in young pigeons.Iron metabolism in birds has received less attention than in mammals. In previous papers we analyzed the plasma iron, the total iron binding capacity and the plasma turnover in chickens, ducks and turkeys [Planas, Castro and Recio, 1961;Planas and Balasch, 1970;Balasch and Planas, 1972]. Ramsay and Campbell [1954] first observed increased plasma iron values during the laying period in chickens and Halkett, Peters and Ross [1958] analyzed the transference of 59Fe from plasma to the eggs in the same species. Godet and Belhani [1974] analyzed blood and organ distribution of 59Fe and Morgan [1975] the plasma iron transport in laying hens and the distribution in some organs; Klein [1959] made similar observations in ducks.The uptake of Fe in red cells in vivo has been analyzed in chickens [Ramsay, 1966], in ducks [Jensen, Ashenbrucker, Cartwright and Wintrobe, 1953] and in pigeons [Hammel and Bessman, 1964] where the Hb synthesis in the adult avian erythrocyte was noted. In pigeons, we recently observed [Palomeque and Planas, 1978] very high values in blood volume, haematocrit, haemoglobin concentration and in heart and breast muscle weights, suggesting an adaptation to flying habits.The present paper extends our studies in iron metabolism in birds and presents some evidence to support this haematological data.
