270 BIRD BEHAVIOUR 



the very soberly coloured females show off simul- 

 taneously with, and with the same gestures as, the 

 highly decorated drakes, which is more than Man- 

 darin Ducks usually do, though they exhibit drake- 

 displays occasionally. In a case I noted one winter 

 when a pair of Blackbirds were disputing over food, 

 I observed both cock and hen running around with 

 trailing spread tails, as cock Blackbirds do when 

 courting. 



As Darwin has remarked, all individuals of a 

 species display in the same way, and he might 

 have gone further, and said that the display is 

 often a group-character, and common to many 

 allied species ; though, on the other hand, one gets 

 sudden differences in this respect between near 

 allies at times, just as one does in the case of notes, 

 eggs, and colouring and decorations. 



The Duck tribe furnish good examples of this ; 

 generally speaking, one may say they never display 

 by drooping their wings, though such a show- 

 gesture is a common one among birds. But display 

 by raising the elbows, and thus erecting the secon- 

 dary quills, is familiar in many species, especially 

 the white and black Swans, though the Black- 

 necked Swan (Cygnus nigricollis) does not practise 

 it ; the males of Ducks most nearly allied to the 

 Mallard rear and curtsey just as that bird does, 

 the plain-coloured species (like the Australian 

 Mallard and Yellow-billed Chilian Teal, Nettium 

 flavirostre) doing so just like the sex-decorated 

 forms, an important point, since it shows the display 



