Estimation of body condition using body mass and external measurements in live Rhinoceros Auklet

Abstract

To evaluate the utility of an index of body condition of live Rhinoceros Auklets (Cerorhinca monocerata), an index obtained from body mass and external measurements was compared to reserved lipid mass measured. Reserved lipid content was extracted using ethyl-ether after the birds had been killed under total anesthesia. The index of body condition was calculated as the residual from the regression of the cubed root of body mass against the first principal component score. This index was called the residual body condition index. The residual body condition index significantly explained 22% and 56% of the variation of the cubed root of reserved lipid mass for males and females, respectively. We could thus reasonably estimate reserved lipid mass of the parents breeding under natural conditions by measuring body mass and external measurements.