Duck : Short-Horn Color Inheritance 



75 



a Such individuals as Rosczvood Radium 512686 are probably of the genetic constitu- 

 tion of RrEe, with respect to color, and could be registered as red-and-white. 



HUMAN CUCKOOS AND HEDGE SPARROWS^ 



The cuckoo lays its eggs in the nests 

 of other birds, as we all know ; and the 

 little cuckoos aid their unnatural mother 

 in her questionable designs by shoulder- 

 ing out from the nest their still smaller 

 foster brothers and sisters. The cuc- 

 koo, moreover, in order to make her 

 own tgg less noticeable when she lays 

 it, at the same time robs the nest she 

 is invading of one of its eggs and eats 

 it ; thus, if I may so describe it, getting 

 a free meal at the public expense. The 

 point is, however, that these immoral 

 birds increase the amount of care given 

 to each of their young ones by dele- 

 gating the whole of their responsibili- 

 ties as parents to several other birds. 



Now, if natural selection in regulating 

 fecundity is, as it were, only looking to 

 the deaths which occur among adults, 

 we should expect to find nothing un- 

 usual in the matter of egg-laying among 

 cuckoos. But if, as I have suggested, 

 fecundity is regulated in accordance 

 with the amount of parental care avail- 

 able for the young, we should expect 

 to find the cuckoo laid more eggs than 

 the nightjar or any other closely related 

 bird with more respectable habits. I 

 confess that I was pleased to find that 

 the cuckoo may lay as many as twenty 

 eggs while the nightjar lays only two.^ 

 It is even more interesting to note that 

 the number of eggs which the cuckoo 



' Excerpted from an article by Major Leonard Darwin. "Observations on Fecundity, 

 in the Eugenics Review for January, 1923. 



^The evolutionary results of the cuckoo adopting these methods must have been sorne- 

 what as follows. The size of the family at first increased considerably, the size being 

 measured at the time when the young birds became independent of parents or_ foster 

 parents. This must have resulted in an increase in the cuckoo population. This in turn 

 led to a rise in the death rate, until the size of the family, if measured by the num.ber 

 of ofifspring who themselves became parents, again fell to two. no more or no less ; that 

 is assuming the population to become stationary. See The Cuckoo's Secret. E. Chance. 

 Sidgwick & Jackson. 1922. 



