THE STIMULATION AND THE INHIBITION OF 

 OVULATION IN BIRDS AND MAMMALS 



WALLACE CRAIG 



The University of Maine 



A previous article (Craig, 191 1) by the present writer showed 

 that in six cases female Ring-Do ves (Turtur risorius) were in- 

 duced to lay by the courting behavior of male doves though 

 the introduction of sperm was prevented. And in one case a 

 female dove laid her eggs in due time after being stimulated 

 merely by a human being who spoke kind words to her and 

 stroked her head and neck in a -friendly way. The opinion was 

 expressed that this last experiment could be repeated if one 

 could get a dove sufficiently tame and willing to show courting 

 behavior toward a human being, as doves sometimes do. 



This expectation was fulfilled in the year 1911, with dove 

 No. 41, a young female which had been reared in isolation, which 

 therefore had had no experience with a dove mate, but regarded 

 human beings as her companions. Human beings were kept 

 away from her cage so far as possible until April 25, when the 

 experimenter suddenly began to spend much time near her 

 cage, to put his hand in the cage, and sometimes to preen her 

 head and neck. The dove began next day to respond to the 

 hand with nest-calling behavior (though she was given no nest) 

 and on May 3 she laid her egg. I now find, too, that the same 

 experiment was performed centuries ago by Harvey, on a par- 

 rot. "Harvey records that, by stroking the back of a favorite 

 parrot (which he had possessed for years and supposed to be 

 a male), he not only gave the bird gratification, — which was the 

 sole intention of the illustrious physiologist, — but also caused it 

 to reveal its sex by laying an egg." (Robinson, 1892, p. 1295). 



It is well known to pigeon breeders that two female pigeons 

 kept together may mate and lay eggs. Some experiments have 

 been made by the writer in mating a female Ring-Dove with 

 another female. In all such cases the two females have gone 

 through a courting performance and in due time both have laid 

 eggs; and after a period of incubation they have repeated the 



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