260 HtrxLEY, Bird-watching and Biological Science. I July 



(2) Courtship-action: What are their details? Are they alike 

 or not in the two sexes? (Great accuracy is needed, not merely in 

 describing the different displays, but still more in following the 

 sequence of events, and so analyzing the birds' mental states.) 



(3) Are there special structures brought into action by courtship? 

 (Peacock, Crested Grebe.) If no special structures, are there spe- 

 cial colors only brought into prominence at courtship? (The 

 Redshank (Huxley, '12) by its actions during display brings into 

 notice the red of its legs, and the white of its tail and of the under 

 surface of its wings, which are usually hidden. The Fulmar and 

 the Kittiwake ^ have the inside of the mouth colored " delicate 

 mauvy-blue" in the one case, "lurid orange-red" in the other (I 

 quote from Selous, '05, pp. 123, 126). This "interior decoration" 

 is displayed in a form of Mutual Courtship. The Ruby-crowned 

 Kinglet gives a very interesting intermediate stage between struc- 

 ture-plus-color and color alone. The crown-feathers are ruby- 

 red and slightly elongated; but the feathers on either side are so 

 inserted as to cover over the bright patch in normal conditions. 

 Only in moments of excitement is the red revealed; and the effect 

 on the hen of such sudden flashing of the brilliant bit of color must 

 be very great.) 



Are there neither special structures nor special colors, but only 

 special actions of courtship? (This is apparently the case in most of 

 the Sylviidse. All observations on similar birds will be of great 

 interest, as in such cases courtship is at its most primitive.) 



(4) Is there a long period of " engagement" or does coition take 

 place immediately after pairing-up? (The latter seems to be true 

 e. g. in the Sylviidse; the former in many birds, such as the Crested 

 Grebe, the Paridse, etc. Facts are sorely needed on this point.) 



(5) What is the relation of the courtship-actions to coition? 

 (In e. g. the Blackcock and Redshank the one is an immediate 

 preliminary and pre-requisite to the other, while in the Crested 

 Grebe there is no direct connection at all, the courtship is "self- 

 exhausting," and special ceremonies of an entirely different nature 

 have been developed in relation to coition.) 



(d) Fighting and Jealousy: (1) Is the fighting between males 



' Fulmarus glacialus and Rissa iridaclyla. 



