268 COLOUR IN NATURE chap. 



this condition are peculiarly ugly, as the bright 

 metallic feathers occur scattered among the dull 

 youthful plumage. If the colours of the male 

 exercise as important an influence on the choice of 

 the female as is commonly asserted for birds, the 

 female sun-bird must also be assumed to be possessed 

 of much faith and foresight. Some at least of the 

 ornamental feathers of the male are cast almost as 

 soon as the breeding season is over. 



Nature of Bright Colours 



The bright colours of the sun-birds are due either 

 to lipochrome pigments or to metallic structural 

 colours, belonging to Gadow's group of subjective 

 structural colours. 



1. Pigmental Colours. — The colours due to lipo- 

 chrome pigments are either yellow or bright scarlet- 

 red. Brilliant patches of red or yellow feathers 

 frequently occur on the throat or on the ventral 

 surface, or dorsally at the root of the tail. The 

 feathers so coloured are always short contour-feathers 

 and not quills. The bright colour is confined 

 to the apical part of the feather, the base being 

 grayish or white, and the pigment occurs as usual only 

 in the barbs. The barbules, if present, are grayish, 

 but most frequently they are rudimentary or absent, 

 so that the visible part of the feather consists of the 

 diverging naked barbs, containing a considerable 

 amount of bright pigment. 



2. Structural Colours. — The metallic colours of 

 the sun-birds occur on feathers arranged in special 

 patches on the head and throat, or as transverse 



