MACROCIIIRES 225 



The swifts are among the very few birds which are 

 partly quintocubital and partly aquincubital. 



Among the more obvious external characters are the 

 magnificent metallic colours which are so usual a feature of 

 humming birds. It is on account of the latter character 

 mainly that they have been placed in the neighbourhood of 

 or more properly confused with the Nectariniida?. It is,. 

 however, practically the universal opinion that these two 

 families have no near relationship, and the feathers of both 

 have been lately submitted to a careful examination by 

 Miss NEWBIG-G-IN. 1 The metallic colours of humming birds 

 occur in both sexes, though more brilliant in the male ; they 

 are mainly to be found on the throat and on the head as a 

 crest. It has been pointed out that the rapidly vibrating 

 wings would destroy all advantage (in sexual selection) of 

 the development of these tints upon the wings. The colours 

 are of every shade, and gold and red are often present, two 

 colours which are not found among the Nectariniidae. The 

 striking difference between the two families, however, consists 

 in the fact that while the Nectariniidas have the ends of the 

 barbs affected by the metallic colour it is the basal part of 

 the barbs which is so coloured in the humming birds. 

 Hence the barbs have cilia in the latter case and not in the 

 former ; for this reason the rectrices in the humming birds 

 can show metallic colours and yet not have their efficiency 

 as flight feathers destroyed. The interlocking apparatus 

 is there in the form of the cilia. The barbs which are 

 thus metallically coloured are in both groups of birds 

 (and in other birds which show the same kind of colora- 

 tion) composed of a series of roof-shaped laminae, in the 

 cavities of which the dark brown pigment essential for 

 the due production of the metallic colour is located. 

 Further details may be found in the interesting memoir 



t/ 



cited. 



The tensor es patagii show a striking resemblance among 



1 ' Observations on the Metallic Colours of the Trochilichi- and the Necta- 

 riniida?,' P. Z. S. 1896, p. '2H3. 



Q 



