1916 ] Huxley, Bird-watching and Biological Science. 267 



Besides Mutual Courtship, another interesting subject is that of 

 social gatherings at pairing-time. I had a little opportunity of 

 seeing the gatherings of the Blue Jaj' last spring in Georgia, and it 

 seemed to me that the gatherings resembled our dances in one 

 respect — in that they " gave opportunities for the young men and 

 women to meet each other." I should welcome all notes on this 

 subject. The Flicker also has gatherings in early spring. As 

 early as February 20th of this year I saw a gathering of ten or 

 twelve in a large tree, but was unable to see anything of what was 

 going on. 



The Swifts and Swallows might prove interesting, especially the 

 former, with their aerial chases of an evening. They are said, 

 apparently on good authority, even to perform the act of pairing 

 in mid-air. 



Next comes another set of interesting problems — those of the 

 reversal of the usual habits and duties of the sexes. The Phala- 

 ropes are the classic instance of this, and would well bear re-investi- 

 gation. On the other hand, all the Hawks and Falcons show it 

 to some extent, and in some ways would more repay watching, 

 since in them the process is still in its early stages. Here, from what 

 few facts are known, it seems that there may be a regular Darwin- 

 ian courtship by the cock; this, in these aerial lords, takes the 

 form of a series of wonderful display-flights. In the Kestrel 

 {Falco tinnunculu^) I myself have witnessed a cock time after time 



As I prophesied in this paper, there is a marked "mutual courtship," though not of quite 

 such an elaborate nature as I had expected from my experience with the Crested Grebe. 

 The most interesting thing about it, perhaps, is the fact that there is a regular honeymoon 

 of two or three days, during which the pair sit together on the nest-site they have just 

 chosen, and, without attempting to start building, are content with running their bUls 

 through each other's aigrettes, huddUng close up to each other, and now and again giving 

 a burst of quite elaborate mutual display — neck raised, wings drooped, and feathers 

 bristled. After this honeymoon, the mutual displays go on, not merely throughout the 

 period of nest-building, taking place whenever a stick is brought to the nest by one bird, 

 to be laid by the other; but right through the time of incubation and care of the young, 

 occurring whenever one bird reheves the other on the nest. 



But at the very beginning, before pairing-up occurs, there appears to be a pure Darwinian 

 courtship, the males showing off their plumage in a special display to the females, who on 

 their peu't do not use their plumes in display at all until after they are paired up. Thus 

 we get Darwinian display before pairing, and Mutual display after pairing — a state of 

 affairs to me at least entirely unexpected, but showing once more how important aie the 

 very earliest manifestations of courtship — the pairing-up habits — and how essential 

 it is to follow the course of events in any one species of bird throughout the whole of the 

 season. 



