I n Ai.i.kx on Sexual Selection ami tin- Nesting of Birds. [April 



upon a misapprehension of the facts in the case, but is suscept- 

 ible of a far more rational explanation. As already noted, Mr. 

 Dixon frankly admits that in the case of dull-colored birds which 

 build covered nests or which nest in holes, "other advantages 

 may be gained irrespective of concealment," and concealment in 

 such cases is considered as unnecessary. These advantages may 

 be in some cases shelter from rain, protection from the sun. or 

 sudden changes of temperature, or greater security from enemies, 

 or concealment of the eggs, which are generally, under such cir- 

 cumstances of nidification, ivliite. or at least conspicuous in 

 coloration. Here, it seems to me, comes in the only function of 

 concealment — namely, that of the eggs rather than the sitting 

 female. 



In my former paper on this subject I referred to this latter 

 point in the following words: "In conclusion. I desire to call 

 attention to an interesting coincidence between the manner of 

 nesting among birds and the color of the eggs, and one so striking 

 that it is almost surprising that some ingenious theorist has not 

 seized upon it as a basis for a 'theory of birds' nests,' either inde- 

 pendently or as a modification of that proposed by Mr. Wallace. 

 It curiously happens that nearly all the birds that nest in holes, 

 either in the ground or in trees, lay white eggs, embracing, fqr 

 instance, all the Woodpeckers, Kingfishers. Bee-eaters, Rollers. 

 Hornbills. Barbets, Puff-Birds. Trogons, Toucans. Parrots. Par- 

 oquets, and Swifts, while only occasionally are the eggs white in 

 species which build an open nest. In only two or three groups 

 of land birds, co-ordinate with those just named, that build an 

 open nest, are the eggs white, namely, the Owls, Humming- 

 Birds, and Pigeons. On the other hand, in only two or three 

 small groups of species that nidificate in holes are the eggs 

 speckled or in any way colored. There is, in fact, a closer rela- 

 tionship, or rather a more uniform correlation, between the color 

 of the eggs and the manner of nesting than between the color of 

 the female parent and the concealment or exposure of the nest. 

 There are. however, here apparently too many exceptions to 

 bring this coincidence into the relation of cause and effect."* 

 Further examination of the matter, however, shows that the 

 coincidence of white eggs and a covered or concealed nest is 

 much more general than the above quotation indicates, the ex- 



* Bull. Nutt. Orn. Club, III, p. 32. 



