The relation of age and sex to the weights of Pink-footed and Grey Lag Geese

Abstract

The goose-netting operations of the Wildfowl Trust provided me with the opportunity of handling more than 1600 geese in the autumn of 1953. My part in this operation was to determine the sex and age of each bird as it was ringed. This was accomplished by examining the tip of the tail feathers for the presence of the tiny notches which distinguish birds of the year from older birds (Hochbaum, 1942). The sex of each bird was then determined by eversion of the vent--a technique previously worked out (Elder, 1946)--to detect the presence or absence of the copulatory organ, characteristic of males in both ducks and geese. Weights were taken to the nearest ounce by means of a spring scale from which a bag was suspended to hold the goose. These weights were later converted to pounds and tenths of pounds to facilitate statistical analysis. A progressive decline in weights from adult males to juvenile females is apparent. it also seems clear that adults are heavier than juveniles of the same sex and that males are heavier than females of the same age group. An analysis of the weights was made in order to discover whether these apparent differences were statistically significant.