4 PROCEEDINGS OF THE NATIONAL MUSEUM vou 80 



Another bird allied to the ruddy ducks, the African white-backed 

 duck {Thalassomis leuconotus), is similarly shy about the nest, and 

 the egg is similarly large in size. 



When a species begins to show a loss of some of the instinctive 

 behavior usually exhibited by the female, one is led to wonder if it 

 may not be becoming what Riddle and others might call a " male 

 species," that is, one in which the females are more malelike and the 

 males " normally " masculine. It is of great interest to find, then, 

 that Wetmore ^^ observed that the female ruddy ducks very commonly 

 mimic the males in display postures and even make a rattling noise 

 with their bills against their cheeks. He noted that this was given 

 at times by females that were apparently unmated. This suggests a 

 latent form of maleness in the females, and I suspect that in these 

 individuals this type of homosexual urge was stronger than in most, 

 and that they were not displaying because they were unmated but 

 were unmated because they were displaying. 



In the tree ducks {Dend7'ocyg7ia) the males take some part, if 

 not the major part, in the incubation of the eggs. Shields ^^ found 

 the fulvous tree duck {Dendrocygna hicolor) to be occasionally 

 parasitic. Another species, Dendrocygna javanica, is known to make 

 use of old nests of cormorants, kites, and crows very frequently. 

 Another instance of increasing " maleness " in the female is shown 

 by the New Zealand sheldrake, Casai'ca variegata. Of this duck 

 Phillips ^^ writes as follows : 



It is a very interesting fact that the female is very forward, very active 

 and very amatory, vrhile the male assumes a rather passive role. Taken in 

 connection with the fact that the young resemble the male, and that the female 

 plumage is so different and perhaps the result of more recent specialization, 

 the relation of the sexes would well repay further investigation * • ♦. 



All Sheldrakes are prodigious fighters, at least during the breeding season, 

 but this species leads them all in strength and combativeness * * *. Here 

 again the female takes the initiative, egging her mate on with loud calls and 

 excited movements. 



For our immediate purpose, however, it is sufficient to know that the 

 females of the ruddy duck are not so " feminine " in their breeding 

 behavior as what we are accustomed to consider " normal," or, to use 

 a better term, usual, in ducks. This diminution of the care of the 

 eggs, coupled with the high frequency of carelessness with regard to 

 the nest in which they lay them, opens the path to joarasitism as a 

 regular, well-established habit. 



Even if we grant the above conditions, the parasitic habit could not 

 become successfully established unless the eggs laid in strange nests 

 materialized into young birds. If they did not, then all this care- 



"Auk, vol. 37, p. 247, 1920. 



^ Bull. Cooper Orii, Club. vol. 1, pp. 9-11. 1899. 



" Natural history of the ducks, vol. 1, p, 253, 1922. 



