COURTING DISPLAY INSTINCTS IN BIRDS. 409 



part not only of the male, but, in some cases, of the female also, 

 suggesting an association of ideas, in the; minds of both, as 

 between this act and the actions and movements in question, 

 through some of which latter, as has been seen, the so-called 

 " false " or " mock nest " of the male is produced. The question 

 also arises whether the nidificatory activities, as well as the 

 courting display actions of birds, may not have originated in 

 such actions as these, thus occurring, whatever the reason, as 

 after-effects of the act of coition.* 



The suggestiveness of the above facts — the great mass of 

 which stand in an actual and not merely an implied relation to 

 (a) the construction of the nest, and (b) a certain earlier use of 

 it than the widely different one, to which it is commonly put — is 

 sufficiently obvious. They lie on the threshold of any inquiry 

 into the origin of the nest-building instinct in birds. They 

 cannot be ignored, they have to be accounted for. My theory 

 accounts for them, binds them, as it were, together, and makes 

 -an understandable whole of them. Therefore it is incumbent on 

 any alternative theory to explain them better, in some other way. 

 That cannot be said to be done by the one put forward by Miss 

 Haviland, viz., that the nest has arisen owing to the desire of 

 the hen bird to shield her . eggs from wet or damp,t for it 

 does not explain them at all ; and that, I think, is a sufficiently 

 destructive criticism, since it is the function of a true hypothesis 

 to explain all facts that are relevant to the issue, and facts 

 which have a strong appearance of being relevant to the issue — 

 as those I have adduced most certainly have— must be deemed 

 to be so until they are shown not to be. Independently, however, 

 of this objection, the view here advanced is, I believe, untenable, 

 for the three following reasons : (1) Because the drastic methods 

 of nature must, far more efficiently and in a far shorter time, 

 have brought about the kind of protection required, through the 

 constant remorseless weeding out of every individual bird or 

 egg not strong enough to live and thrive under the ordinary 

 conditions of its environment (which, by the way, include tepid 



* ' Zoologist,' April, 1902, pp. 136-9 ; May, 1902, pp. 196-7 ; June, 1906, 

 pp. 201-4, 209-10, 212. The ' Scottish Naturalist' ("The Display of the 

 Mallard," S. E. Brock), p. 80. 



f ' Zoologist,' p. 244. 



