210 THE BIOLOGY OF BIRDS 



Male. Female. 



Sperm-producer Egg-producer 



With less expensive reproduction With much more expensive repro- 

 duction 



More intense metabolism Less intense metabolism 



Relatively more katabolic Relatively more anabolic 



Often with shorter life Often with longer life 



Often smaller Often larger 



Often more brilliantly coloured Often quieter in colour and plainer 



and more decorative in decoration 



Rising to more intense outbursts Capable of more patient endurance 



of energy 



More impetuous and experimental More persistent and conservative 



More divergent from the youthful Nearer the youthful type 



type 



Often more variable Often less variable 



Making more of sex-gratification Making more of the family 



Sex-Characters in Birds. — Turning to birds more par- 

 ticularly we may cite a number of representative illustrations 

 of sex dimorphism, referring for further detail to Darwin's 

 " Descent of Man," Cunningham (1900), and Meisenheimer 

 (1921). The climax is to be found among Birds of Paradise 

 (Paradiseidae), Humming-Birds (Trochilidas), and Game- 

 birds (Phasianidae). 



Among Birds of Paradise the females are more or less 

 soberly coloured, the males are resplendent and show 

 specially exaggerated feathers which are erected and often 

 vibrated. The males often congregate in a tree and hold 

 what the natives call a dancing party. " In the Great Bird 

 of Paradise, Paradisea apoda, which is found mostly in the 

 Aru Islands, the chief ornament is the great bunch of long 

 and delicate plumes on each flank. These plumes are of 

 an intense golden-orange colour, changing at the tips into 

 pale brown, and are sometimes two feet in length. When 

 erected and made to vibrate, they form a sort of golden 

 fountain almost concealing the body of the bird. In the 

 female all the ornamental plumes are wanting, and the 

 colour is a uniform coffee-brown " (Cunningham, 1900, 



P- 139)- 



Among humming-birds, again, the males are usually 



very much more resplendent than the females. The decora- 

 tions take the form of tufts which can be erected, of greatly 



