296 SOME OBSERVATIONS ON 



confirm the fact which Mr Youell has pointed out, namely, 

 that a change in the colour of the plumage of Birds does not 

 always arise from a change of feathers, but sometimes pro- 

 ceeds from the feathers themselves assuming at one season of 

 the year a different colour from that which they have at ano- 

 ther*." 



The Rev. Dr Fleming, in his Philosophy of Zoology, cor- 

 roborates the above opinion of the Rev. Mr Whitear's ; but 

 maintains, that, " in those species whose plumage changes co- 

 lour with the season, the different moultings take place at 

 corresponding periods." "In the autumn," continues he, 

 " we find that the black feathers on the head of the Larus ri- 

 dibundus change to a white colour. But besides the altered 

 feathers, others spring up, of a white colour, to increase the 

 quantity of clothing. This Gull has, therefore, during the 

 winter, some of the feathers of the head old, and others young. 

 Again, in spring the white feathers of the winter become 

 black, and a few new feathers make their appearance, like- 

 wise of a black colour, to supply the place of the older ones, 

 which drop off in succession. Some of the feathers on the 

 head of this Gull are half a year older than others ; and con- 

 sequently, we may infer, will fall off sooner than those of 

 more recent growth. From these, and similar facts, furnish- 

 ed by several species of British birds, we are disposed to con- 

 clude, that the feathers which are produced in autumn, and 

 the beginning of winter, and which correspond with the con- 

 ditions of the season, change their colour in spring, and con- 

 tinue in this state until they are shed in autumn. The 

 feathers which are produced in spring, continue of the same 

 hue during the summer, change their colour in winter, and 

 fall off again upon the approach of spring. In this manner, 

 the quantity of the plumage fit for the different seasons of 

 the year is easily regulated ; and it is only necessary that the 

 change of colour in each feather should take place but once 

 in the course of its connection with the birdf." 



* Transactions of the Linncan Society of London, vol. xii, p. 524. 

 t The Philosophy of Zoology, vol. ii, p. 28. 



