Bech, C. and M. Klaassen (1996). Blood hemoglobin content and metabolic performance of Arctic Tern chicks Sterna paradisaea. J. Avian Biol. 27: 112-117.

This study was designed to determine whether the development of an increased aerobic capacity (increased potential for oxygen uptake) during the initial growth stages of hatchlings is associated with an increase in blood hemoglobin content. We measured the resting (at thermoneutrality) and maximum (cold induced) oxygen uptake in Arctic Tern chicks from 0 to 9 days of age. In addition, blood hemoglobin content and hematocrit were measured. The results show that in spite of a marked increase in both resting and maximum oxygen uptake, indicating increased metabolic performance, there was a slight decrease in blood hemoglobin content during the first few days of development. A residual analysis, made to eliminate the effect of age, showed that blood hemoglobin content was not significantly correlated with either resting or maximum oxygen uptake. The conclusion is that, despite a wide variation in the hemoglobin content of individual chicks, blood hemoglobin content is not a limiting factor for oxygen uptake by Arctic Tern chicks.