Haematological changes during development of the noisy miner: implications for oxygen transport

Abstract

Changes in erythrocyte numbers and size, haematocrit and blood haemoglobin concentration in noisy miner (Manorina melanocephala) nestlings were documented from measurements taken on wild individuals during development. Haematocrit, whole-blood haemoglobin concentration and erythrocyte count increased during development by factors of 2.0, 2.4 and 3.5, respectively. The increases were continuous and occurred at fairly constant rates throughout development, but typical adult values were not attained at fledging. Mean erythrocyte volume and mean erythrocyte haemoglobin content decreased continuously during nestling development. The estimated 2.4-fold increase in oxygen carrying capacity of the blood during development stemmed primarily from the increase in erythrocyte numbers. The reduction in erythrocyte volume would be expected to enhance oxygen delivery by increasing oxygen-diffusion rates. This pattern of constant change in blood parameters resembled that reported for species with standard, rather than unusually slow, rates of nestling development. We suggest that it reflects the fact that noisy miner nestlings grow relatively rapidly, perhaps because it reduces the exposure of nestlings to predation.