Haematological changes during development of the noisy miner: implicationsfor oxygen transport

Changes in erythrocyte numbers and size, haematocrit and blood haemoglobin concentration in noisy miner (Manorina melanocephala) nestlings were docume nted from measurements taken on wild individuals during development. Haemat ocrit, whole-blood haemoglobin concentration and erythrocyte count increase d during development by factors of 2.0, 2.4 and 3.5, respectively. The incr eases were continuous and occurred at fairly constant rates throughout deve lopment, but typical adult values were not attained at fledging. Mean eryth rocyte volume and mean erythrocyte haemoglobin content decreased continuous ly during nestling development. The estimated 2.4-fold increase in oxygen c arrying 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 rate s. This pattern of constant change in blood parameters resembled that repor ted for species with standard, rather than unusually slow, rates of nestlin g development. We suggest that it reflects the fact that noisy miner nestli ngs grow relatively rapidly, perhaps because it reduces the exposure of nes tlings to predation.