NOTES AND QUERIES. 463 



this feature was sufficiently marked to suggest the word to me. I 

 however mention the birds touching each other's bills. " Nebbing " 

 and "billing" are the two English words; but, not liking either of 

 them, I inadvisedly used a French one, thinking it expressed a little 

 more than our " touch." At the least, therefore, this action must 

 have appeared the most important one to me — the central act, so to 

 speak — and adds (I think) another to those recorded in the paper in 

 question. But if this be so, the question arises as to what is its 

 value in the philosophy of the whole — of the shaking bout, that is to 

 say, whether accompanied by this action or not. May it not, as 

 being far more widely extended amongst birds than this very 

 specialised form of nuptial enjoyment, have been the root feature, 

 out of which the latter grew, and at last became overgrown? If so, 

 the case, I think, does not want parallels. The fact that, when I 

 witnessed the equivalent (in this I am inclined to agree with 

 Professor Huxley) of these shaking bouts, it was later in the season, 

 and the birds were satisfying their sexual instincts, through a fuller 

 channel, may have tended to reduce them to something more like 

 what they originally were, before they became thus exaggerated. 

 The question involved is whether the singularities of the courtship 

 habits of the Great Crested Grebe may not be due to various 

 subsidiary causes, not essentially or unmixedly belonging to sexual 

 selection, or else have been evolved pari passu with the more 

 ordinary manifestations of this principle, or through a combination 

 of these two factors, in which case they need not represent any 

 essential addition to such a course of procedure as, in many 

 birds, during the love season, seems exactly in accordance with 

 the requirements of the Darwinian theory." It may, I think, 

 be asked whether "mutual" or "double selection," as between the 

 sexes, constitutes such an addition. Darwin considered the likeli- 

 hood of this principle obtaining in Nature, and though he concluded 

 against it, yet he evidently regarded it as comprised potentially in 

 his views. His opinion, however, was based rather upon general 

 considerations than actual evidence, of which there was little or none 

 at the time. During a visit to the Shetlands, in 1900, I came to the 

 conclusion that there was some amount of reciprocation, in display 

 and choice amongst birds, and in a chapter of the book f in which 



:;c I have recorded very salient examples of this, in the case of the Bed- 

 shank, Ruff, and Blackcock, in ' Zoologist,' 1906, pp. 201, 285, and 419 ; 

 1907, pp. 60, 161, and 367 ; 1909, p. 401 ; 1910, pp. 33, 51, 176, and 248. 



\ 'The Bird Watcher in the Shetlands.' 



