1977 年 9 巻 3 号 p. 284-285_4
A particular female Whooper Swan Cygnus c. cygnus, wintering at the well known swan and other waterfowls resort, lake Hyoko, was kept under observation in 1976-77 winter. Here the swans and waterfowls are well tamed by artificial feeding. This particular female arrived at Hyoko in late December with her mate and 2 cygnets. In my first observation in December, her crown seemed to be somewhat unkempt, but it was not so curious.
As the time went by her crown feathers became longer. This changing process is shown by Plates 13-16.