Ontogeny of Oxygen Consumption by Embryos of Two Species of Swallows (Hirundinidae)

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Abstract
Bank [Riparia riparia] and barn [Hirundo rustica] swallow embryos show an exponential increase in O2 consumption (.ovrhdot.MO2) during development with a substantial rise in .ovrhdot.MO2 occurring upon hatching. The pattern observed in these species is similar to that observed in other altricial birds. Measured pre-pipping .ovrhdot.MO2 values (1.45 and 1.75 cm3O2.cntdot.h-1, respectively) agree well with those predicted on the basis of egg weight, but diverge markedly from predictions based on incubation time and water vapor conductance. This supports the recent proposal of Hoyt, et al. (1978b) that air cell O2 tensions are positively related to initial egg weight and that the relationships predicting pre-pipping .ovrhdot.MO2 on the basis of incubation time and water vapor conductance need to be re-examined.