64 The Irish Naturalist March, 



summer dress. She is more active, carries on the major part 

 of the courtship, and omits to take on herself the task of 

 incubation. 



It is often difficult to explain adequately the reasons why- 

 some birds differ sexually in size and colour. The following 

 is a short paragraph which I take the liberty to quote from 

 J. T. Cunningham's recent work on " Sexual Dimorphism." 1 

 With reference to the Grey Phalarope he writes : — " The 

 females are larger and in their summer plumage more gaily 

 attired than the males, and according to Professor Steenstrup 

 the male of Phalatopus fulicarius alone incubates. The females 

 do not appear to fight, and their greater size must be attri- 

 buted to their greater activity, for the sex which incubates is 

 necessarily the more sedentary. The more intense colouring 

 of the female is probably merely due to its greater sexual 

 excitement, as it is difficult to perceive anything in the 

 external influences, such as light or food which could affect 

 the sexes differently " (p. 155-156). 



To sum up : from the preceding remarks we find that the 

 sexual features of the female Grey Phalarope as contrasted 

 with the male are these : — 



1. larger. 



2. Brighter in colour. 



3. More active in habits. 



4. Displays greater sexual excitability. 



5. Female never incubates. 



Taken together, these five characters belong to the vast 

 majority of male birds. With the Phalarope for some unknown 

 reason, the males seem to have become effeminated, leaving 

 the active part of the courtship to be conducted by the 

 females. Relative to this subject Darwin 2 stated, when 

 treating of the subject of sexual dimorphism in general in 

 birds, that here " sexual selection would do its work, steadily 

 adding to the attractions 3 of the female ; the males, and the 

 young birds being left not at all or but little modified." 



Sexual Dimorphism of the Grey Phalarope with reference to 

 protective colouration. — I do not think that the male is more 



1 London, 1900. 



2 " Descent of Man," p. 480. 



3 Greater size, strength, activity, superior colour, vocal power, &c. 



