AGE-RELATED VARIATIONS IN BILL SIZE OF CHINSTRAP PENGUINS

Adult breeding Chinstrap Penguins (Pygoscelis antartica) have larger b ills than one year old individuals, whereas the flipper length does no t differ. Therefore, bill size increases with age during the juvenile stage. The allometric relationships of both bill length and bill depth with flipper length do not differ between age groups. The relation of bill length with bill depth does not differ between adults and juveni les, suggesting no change in bill shape with age. If the random sample s of adults and yearlings represent a similar proportion of males and females, these results do not support sex divergence in bill growth af ter the first year of life.