飼育下のウミネコの年齢による尾羽模様の変化

抄録

Black-tailed Gulls Larus crassirostris have a black band on the upper tail. I measured the length from the tip of the tail to the outermost edge of the black band (white fringe on tail edge) of 22 captive individuals in the Ueno Zoological Gardens. The length of the white fringe increased in relation to the age of each individual. Therefore, it was suggested that the age of Black-tailed Gulls can be determined by the length of the white fringe until at least four or five years of age.