Vol 

 1903 



2 'J Lf, SouEF, Birds Chatiging Colour of Plumage . 1 97 



the markings will be observed extending more towards the 

 end ; in No. 3 the white spaces are enlarging, and as the dark- 

 coloured pigment is getting more concentrated, also in rows, it 

 is becoming darker in colour ; in No. 4 the lines are definite 

 throughout the feather, but irregular ; and in No. 5 they are 

 more definite still, although the feather has not yet quite 

 reached its perfect stage. In the next four, another series, 

 exactly the same thing will be observed, and again it will be 

 noticed how the brown pigment gradually becomes almost 

 black, as in the perfect feather, when it is concentrated into 

 narrow bands. The bottom row of three feathers shows the 

 same stages. 



In the second exhibit exactly the same stages will be noticed 

 in the feathers taken both from the back and the breast of the 

 bird, and here again it is apparent that the brown becomes 

 almost black when it is concentrated into narrow bands.* 



Again, in many birds the beak also changes colour, especially 

 in sea birds — for example, the beak of the White-capped 

 Albatross {Thalassogeron cautd), and also that of the Pacific 

 Gull {Larus pacificus), are black when the young are nestlings, 

 but gradually change until by the end of the third year they are 

 of a yellowish-brown colour. 



Of course this subject is well known to many ornithologists, 

 but practically not at all to the general public, who consider 

 that birds always moult when changing colour. 



The age at which change occurs varies in different birds. 

 Most small birds change in the first year ; others, such as 

 parrots, in the second ; but probably the bulk of the larger birds, 

 such as Pacific Gulls, Ibises, Emus, &c., do not change until the 

 third year. Probably the longest time of all is taken by the 

 Satin Bower-Bird {Ptilonorhynchus violaceus), which does not 

 get his rich glossy bluish-black plumage until he is about seven 

 years old. He is then very conspicuous, and consequently 

 more liable to get destroyed by birds of prey than his green- 

 coloured companions, and that probably accounts for there not 

 being as a rule more than one blue male with a flock of these 

 birds, as they always live in companies. 



[Mr. Le Souef has diverged into a field of study which has occupied the 

 minds of many European and American ornithologists, and is to be con- 

 gratulated for so doing. But the issue dealt with by the writers to whom 

 he makes passing reference is somewhat different to that he has touched 

 upon in his paper. It concerns more immediately seasonal change of 

 colour in plumage than that change which accompanies the maturation of a 

 bird, many instances cited being those of birds which whilst in Arctic 

 regions wear a white or very light-coloured garb, and on coming south to a 

 warmer climate assume a brownish or even darker hue, resuming their 

 lighter garb when they again go towards the Pole. This is a phase of the 



* The illustration hardly shows them in exactly the same colour as they are in 

 nature, and therefore the changing from brown to nearly black will not be noticed 

 so clearly. — D. Le S. 



