Sex Ratios in Pigeons. 
499 
Pigeon has laid her first Egg, she rests one Day between, and on the 
succeeding Day lays her second: They generally stand over the first 
Egg, which if you please, you may call an improper Incubation, till the 
next is laid, and then sit close, that both young ones may be hatch’d 
at once, or pretty nearly; tho’ some will sit close on the first, and 
by that means hatch one young one two Days before the other.” 
Mr. Kelley states that from his observations he is of the opinion that 
whereas the hen stands over the first egg in this manner, the cock, 
when he is on the nest, sits much closer and thus the egg receives 
some incubation before B is laid. This partial incubation probably 
accounts for the half-day which A hatches on the average ahead of B. 
That this is the case is further indicated by the fact that by candling 
the eggs a day or so after the laying of B the embryo may usually be 
seen to be in a further stage of development in A than in B, its greater 
development evidently representing the incubating it has received 
before B was laid. 
Even though we may not be willing to accept the teleological 
explanation of Moore for the behavior of the female in not incubating 
the first egg, we must admit nevertheless that it has important 
biological significance. It is a well established fact for other birds 
as well as for pigeons that the parents use no judgment in feeding the 
young, but always fill up first the youngster which is most insistent. 
In this way it is the most active and vigorous individual which is 
first satisfied with food. While this may tend toward the survival 
of the fittest in a brood, it is also an example of failure in biological 
regulation. It would seem as if it were better, so long as the food 
supply was sufficient, for the parents’ instincts to lead them to feed 
first the retarded individuals, and thus give all in the brood an equal 
chance. However this may be, every pigeon raiser knows that where 
there is much difference in size between the two squabs in a nest, the 
smaller rarely has much chance of survival unless it is given special 
attention and care. Disadvantageous difference in size is very 
frequent in pigeons, and it is our practice to exchange squabs (marked, 
of course, for identification) in nests of this sort, so as to bring together 
