iSSj.] Allen on Sexuaf Selection and the Nesting oj Birds. I2Q 



SEXUAL SELECTION AND THE NESTING OF 

 BIRDS. 



BY J. A. ALLEN. 



Mr. Henry Dixon, in a paper "On the Protective Colour of 

 Eggs,'* follows Mr. A. R. Wallace in dividing "birds into two 

 great classes— one in which the sexes are alike and of conspicu- 

 ous or showy colours, and which nidificate in a covered site ; and 

 the other in which there is a marked difference between the 

 colour of the sexes, the male being showy and the female sombre, 

 and which nidificate in an open site" ; and he subdivides them 

 "into several minor groups, which will include all the 'exceptions' 

 to either great rule." Having' once written on this subjectf 

 I return to it reluctantly, and only because there seems to be 

 something still to say on the other side. 



Mr. Dixon's first group consists of "Birds in which the plu- 

 mage of the male is bright and conspicuous in colour, and that of 

 the female dull and sombre, and which nidificate in open sites." 

 Under this heading, in referring to the fact that "the plumage of 

 the female bird is in a great many cases far more sombre than 

 that of the male." he says: ''Until recently the cause of this 

 phenomenon was never dreamed of. It is an ascertained fact that 

 the colour of many female birds is connected in no small degree 

 with their mode of nidification , and that the sitting bird is pro- 

 tected by the harmony which exists between its own sober plu- 

 mage and the colour of the surroundings of its nesting site. Let 

 us glance over the nesting-habits of some of our best-known birds. 

 and learn the working of this law." As examples of this great 

 group he cites certain Pheasants and Grouse, various Ducks, the 

 Blackbird {Merula merula) and Ring-Ouzel { M. torqttata) . 

 several Finches and the Stonechat (Pratn/cola riibicola) . in 

 which 'the diversits of plumage between the sexes' shields the 

 female during the season of nidification. In most of the 

 instances cited this is eminently true, but there are glaring excep- 

 tions. Indeed, it will readily occur to ornithologists that several 



* In Seebohm's 'History of British Birds,' Vol. II, Introduction, pp. x-xxxii. 



t Sec paper entitled 'An Inadequate "Theory of Birds' Nests," ' in Bull. Xntt. Urn. 

 Club, Vol. Ill, 1878, pp. 23-32. 



