Sulphur-crested cockatoos are large birds, measuring 45 to 50 centimeters in length. Their average weight is 800 grams. Sulphur-crested cockatoos are white with a distinctive sulphur-yellow crest which can be erected or held folded down on top of head. The underside of their wings and tail is pale yellow. Females and males are similar in appearance (monomorphic); however, females can be identified at close range by their red tinted brown eyes, whereas males have darker brown eyes. There are four subspecies of sulphur-crested cockatoos. Cacatua galerita fitzroyi differs from C. g. galerita in having a pale blue eye ring instead of white, the yellow feathers are slightly darker, and the crest feathers are longer. Cacatua galerita eleonora and C. g. triton both average smaller in overall size than C. g. galerita. (Australian Museum, 2003; Bell, 1969; Dobbs and Highfill, 2003)