THE PAIRING OF PIGEONS. 35 



masculine female has more often been the "jealous" driving one. I have failed to note 

 different roles taken in "nest-building." 



In sexual "billing" the more masculine bird usually, but not invariably, receives the 

 bill of her consort. Sometimes, however, in the rather tense sharp contest on this much- 

 indulged detail, the more feminine female is induced or forced to yield her open mouth; 

 in which event she is more often induced to follow this by mounting than when the billing 

 contest terminates differently. She may, however, play the part of the male in the "bill- 

 ing" and yet function as a female in the succeeding copulation. In general, the one that 

 usually "bills" as a male. also "jumps over" and mounts, as a male. Important here 

 too is our finding that such a masculine member of the pair is usually a day or more behind 

 her mate in egg-laying, and may not lay at all! 



It is evident, therefore, that those females which mount as males much more than 

 do their consorts are rather consistently masculine towards these consorts. But, as stated 

 above, where quite free and unopposed their activities are those of females. This fact 

 must not be disregarded. Whether a pair of females maintain this sort of differentiation 

 during the incubation period is a matter not yet tested; in fact, this may not prove easy to 

 decide since most female doves seem willing to go to the nest by day whenever the eggs 

 are left uncovered; and both, or either, will sometimes sit at night in cases where both 

 have laid eggs. This matter certainly needs further investigation. 



PAIRING OF MALES. 



Males have also been known to mate. Two of my male passenger-pigeons mated with 

 each other, notwithstanding they were in a pen where there were several unmated females 

 desirous of mating. (C 7/48.) 



Dr. Riddle has noted the same phenomenon and has furnished the following 

 account of the behavior: 



The mating of male with male has been seen to occur among certain doves. That is 

 to say, two males may pair, cease to drive or fight each other, mutually defend a nest, 

 and either or both actively, and with apparent completeness, take the part of a female 

 in copulation. Thus mated they may go through the whole of the breeding cycle of 

 copulation, nest-building, feeding, and rearing of foster young. The few cases of such 

 matings that I have thus far observed present, however, widely varying degrees of com- 

 pleteness of the mating. Only a single pair of (young) blond ring-doves has been seen to 

 carry out the entire program stated above. 



The male birds thus far known actively to take the part of a female in the sexual act 

 are blond rings (St. risoria), white rings (St. alba), and hybrids between the Japanese 

 turtle-dove (T. orientalis) and the white rings. Among these forms matings are more 

 easily secured if young males are used. The latter statement can now be made confidently, 

 though the first mating observed was between two orientalis-alba hybrids whose age was 

 4 or 5 years. The fact that one of these birds seemed actively to function as a female, in a 

 copulation which I chanced to see, led me to make several matings with a view to a study 

 of this situation. I had already learned that the sisters of these same hybrids, of all ages, 

 can be made to mate with each other under certain conditions. A number of pairs of 

 mature males were isolated; some of these were observed for several months, but no real 

 matings resulted from any of these cases. Even the pair of birds which was first seen to 

 copulate, in a pen where there were only male birds, fought and drove each other when 

 isolated from the group. Between these two birds very few matings were later observed 

 which could give any reason to believe that one was really and actively functioning as a 

 female; both birds of course occasionally attempted the part of the male in copulation, but 

 to the end fierce fighting was the rule of the day in this cage as it was in the others. 



