264 Huxley, Bird-watching and Biological Science. [july 



pairing-up. Personally I believe that the above facts should be 

 interpreted thus — that the cocks fly up to the hens, either indis- 

 criminately, or more probably, I believe, to those they uncon- 

 sciously prefer; the hens in their turn either do not feel drawn to 

 the suitors, in which case they reject them by repeatedly flying 

 away, or else they are in their turn attracted by one of the cocks. 

 This attraction depends on three factors; — (i.) the physiological 

 state of the hen; (ii.) the instinctive mental (psychic) preference 

 felt by the female for particular males, which must exist in birds 

 as well as it obviously does in Man, though perhaps in different 

 degree; (iii.) the persistence of the cock, which will tend to win 

 the hen if she is doubtful but not unfavorably inclined, although it 

 will make her more obstinate if she is repugnant from the first. 



Once a hen consents to let a cock come right up, the next step is 

 not coition, of which there is no question for many weeks, but this 

 mutual courtship-action which to me appears as the link binding 

 the pair together before the time of fertilization and nest-building. 

 Be this interpretation as it may (and I confess that there are many 

 little gaps yet to be bridged over), I yet have some definite facts, 

 and they are filed as follows. 



In the card-index the Killdeer (Oxycchus vociferus) comes under 

 the family Charadriidce, with the A. O. U. number 273. In my 

 vertical file is a folder labelled 273 Killdeer. In this are my notes, 

 under dates Feb. 7, 15 and Feb. 21, 15. In the card-index after 

 the card of the species follows a card labelled (a) with the remark 

 "common in small flocks throughout winter, Houston." Then 

 one labelled (b), on which is written; 



Approach flights of d^ Feb. 



Chase of 9 by cf Feb. 



Chase repeated twice Feb. 



Some birds paired Feb. 



Paired birds going through a 



ceremony Feb. 7, 15 



When I have some more data, I shall go through all my facts and 

 write a short summary of the pairing-up on another card which will 

 also bear the heading (b). 



The general system is now clear; it can be easily modified to 

 suit anybody's ideas. Its chief advantages are ease of reference, 



