^58 Huxley, Bird-walching and Biological Science. [july 



together into flocks containing four or five species. I have seen 

 three species of Paridse (P. major, P. coeruleus and P. ater) to- 

 gether with Goldcrests (Regulus cristatus) and Creepers {Certhia 

 familiaris) all travelling together through the tree-tops.) 



(2) If the flock is the unit, does the pair persist within the flock? 

 (c/. the Dabchick, cited above, p. 149). In some birds this is 

 definitely not the case, since the sexes separate and the flocks are 

 almost all of one sex: e. g. Fringilla coelebs, the Chaffinch.) 



(3) In migratory birds, is the unit the same all through these 

 months, or do the migrating flocks break up into pairs or individuals 

 in their winter home? 



(4) Is there any recrudescence of courtship-action in early fall, 

 or in warm days in winter? (After family duties are over and 

 before there is any scarcity of food, many birds go through a modi- 

 fied form of courtship. I have seen a pair of Kingfishers (Alcedo 

 ispida) in October, in England, very obviously "courting." It 

 would be of great interest to know in what ways the courtship of 

 autumn differs from the typical courtship. A warm day in late 

 winter often seems to arouse the dormant sexual actions, just as it 

 induces a first attempt at song. This January I saw a Hermit 

 Thrush, though c^uite alone, several times go through the motions 

 of depressing the tail and drooping and spreading the wings, which 

 on the one hand are the regular motions accompanying coition, 

 and secondly have afforded the basis (by association of ideas) for a 

 large number of the beautiful ceremonies of display.) 



(b) Actions connected with the heginning of the breeding season: 

 (1) Is the species polygamous, polyandrous, promiscuous, or 

 monogamous? If the last, does it pair for the season, or for life? 

 (This question must be answered first, for naturally all the court- 

 ship will stand in relation to the answer to it. One very important 

 point is the numerical proportion of the sexes. In some of the 

 Game-birds it appears that there may be a large excess of males, 

 but in most species the numbers are pretty equal. It is obvious 

 that this point will have an important bearing on courtship, and it 

 figures prominently in discussions of the Sexual Selection theory.) 



(2) In those birds that are not monogamous, what actions 

 initiate the breeding season? (very little is known on this point.) 



(3) In monogamous birds, what is the date of pairing-up? 



1J 



