COLOR AND SEX. 



45 



exact value remains to be determined by closer obser- 

 vation. 



Color and Sex.* It is not possible here to discuss at 

 length the vexed question of sexual coloration. But, as a 

 means of directing observation, I present a synopsis of 

 the principal types of secondary sexual characters, with 

 some of the theories which have been advanced to ac- 

 count for them. 



SYNOPSIS OF THE SECONDARY SEXUAL CHARACTERS 

 OF BIRDS. 



Size. 



Plumage. 



Of the body. 



Of the feet. 

 Of the bill. 



Pursuit. 



Display. 

 Battle. 



Music. 



Special 

 habits. 



I. STRUCTURAL. 



Male larger than female (usual). 

 Female larger than male (rare). 



J ^ a ^ e brighter than female. 

 ( Female brighter than male (rare), 

 f Assumption of plumes, ruffs, crests, trains, 

 etc. : special modification of wing and tail 

 Form. \ feathers. 



| a. Worn by male alone. 

 [ b. Worn by both sexes. 



Sole or greater development in male of brightly col- 

 ored bare tracts of skin, combs, wattles, caruncles, 

 and other fleshy or horny appendages. 

 Sole or greater development in male of spurs. 

 Male with more highly colored or larger bill than 

 female. 



II. FUNCTIONAL. 



By male when similar to or brighter than female. 



By female when brighter than male. 



By male of accessory plumes and other appendages. 



By male using spurs, wings, bill, etc. 

 ( Vocal, by male and, rarely, female. 

 \ Mechanical, by male and sometimes female. 



I Dances, mock fights, aerial evolutions, construction of 

 bowers, decoration of playgrounds, attitudinizing, 

 strutting, etc. 

 a. By male before the female. 

 6. Among the males alone. 



* Read Darwin, The Descent of Man and Selection in Relation to 

 Sex (D. Appleton & Co.). Wallace, Darwinism (Macmillan Co.). 



