II. CHANGES IN THE COLOUR OF THE 



PLUMAGE OF BIRDS WITHOUT 



MOULTING 



A PHENOMENON of great and peculiar interest in the life of birds 

 is connected with the alteration of colour undergone by the plumage 

 in the formation of the breeding dress without the renewal of the 

 feathers by moulting. In regard to this process, Heligoland sup- 

 plies us with an abundance of material for observation, and having 

 for many years devoted considerable attention to the subject, I 

 cannot omit at this time to place before the reader the most obvious 

 results of my investigations. 



Schlegel, in his Sendschreiben an die in Altenburg versam- 

 melten Naturforscher, 1 published in 1852, was the first to express 

 himself in an incisive manner on this subject, and the surprising 

 novelty of his statements at once provoked the liveliest discussion. 

 The majority of observers, however, showed themselves decidedly 

 opposed to Schlegel's conclusions (C. L. Brehm, E. von Homeyer), 

 while from a few others they received at least partial confirmation 

 (Martin, Gloger). On the latter side may be ranged my own 

 reports on the subject, which, though they failed to agree with 

 Schlegel's statements in a few particular instances, nevertheless, 

 gave general recognition to the fact that, in the case of a large 

 number of birds, a great number of the feathers of the plumage 

 resulting from the autumn moult underwent, during the following 

 spring, a complete alteration of colour. 



For a few years afterwards the subject was occasionally dis- 

 cussed in ornithological journals, but subsequently, so far as I 

 know, received no further notice. I for my part, however, have 

 devoted the most unremitting attention to it ever since that time, 

 with the result of finding my own earlier conclusions fully corro- 

 borated ; while, at the same time, the investigation of a very large 

 number of fresh spring birds has further convinced me of the accu- 

 racy of one of Schlegel's statements, which I had before considered 

 untenable, to the effect that the margins of the feathers of many 



1 Circular addressed to the members of the Naturalists' Congress at Altenburg. 



