72 Heer F. E. Blaauw on the 



with a dark mark on the occiput. The bill and legs are 

 black. These birds grow very rapidly, much more quickly 

 than the young of the Bernicles and their allies. The first 

 plumage is extremely beautiful, especially when the feathers 

 are just appearing between the still conspicuous patches of 

 down. The birds then look as if they were clad in un- 

 burnished silver. Later, much of the delicate beauty of 

 the coloration fades, and the plumage may then be described 

 as follows : — 



General colour silver-grey (with a very slight brownish 

 tinge), darkest on the back and hind part of the neck, and 

 nearly white on the breast and belly. There is a dark mark 

 on the occiput, which is also observable in the downy dress. 

 Each of the darker grey feathers of the back has a white 

 edging, varying in width. The tail-feathers are white, with 

 a grey spot in the centre. The large night-feathers are 

 black, although the black is not so intense as it is in the 

 adult bird. The bill and legs, which are black in the chicks, 

 soon become brighter. The bill gradually passes from black 

 to pink. The legs, however, first change from black to 

 yellowish grey or greenish, and to pink afterwards. In 

 October the first white feathers begin to appear, and the 

 birds gradually assume the white dress of the adult. 



In former years* I have repeatedly bred young birds from 

 a male of the Blue Snow-Goose (Chen carulescens) and a 

 white female of Chen hyperboreus , when the results of the 

 union have invariably been Blue Snow-Geese, and not 

 specimens intermediate in plumage between the two forms. 

 This year a pair of these Blue Snow-Geese (the result of a 

 mixed union) has bred, and the result has been a brood 

 of four young, all recognisable at once as true Blue Snow- 

 Geese. 



The chicks of the blue form are quite different from those 

 of the white form, being of a dark olive-green, darkest on 

 the back and on the head, which is almost black. The first 

 plumage is slaty grey throughout, being darkest on the head, 



* SeeP.Z. S. 1899, p. 413. 



