MovvAT. - Colours of Birds. 



47 



will build in a tree if other sites are scarce. The nesting- 

 sites it chooses are, in fact, so extremely various that 1 

 think only a very stupid pair of Sparrows could fail to 

 suit themselves somehow. And thus I think the plumage 

 of the House-Sparrow cjuite naturally follows the common 

 rule, being dull in the hen but decorative" in the cock. 

 Hut this difference in the Sparrows is of peculiar interest, 

 because the House-Sparrow has a near relative, the Tree- 

 Sparrow, which follows the opposite rule. The cock of 

 the Tree-Sparrow is quite as ornamentally plumaged as 

 the cock of the House-Sparrow ; but the hen of the Tree- 

 Sparrow is as bright as the cock, and scarcely distinguishable 

 from him. And what is the corresponding difference of 

 habit ? Just ^hat we might expect. The Tree-Sparrow 

 makes a regular practice of nesting in holes— holes in the 

 strictest sense of the word, and nOt mere crevices such as 

 satisfy its better-known cousin. I have no personal 

 acquaintance with the habits of the Tree-Sparrow ; but I 

 think it will be found that in the battles in which birds 

 of that species must sometimes engage for possession of 

 nesting-rights the cock-birds are not left to light ?lone, 

 but get good support from their wives. 



There are, I think, only two British birds that nest in 

 holes (other than mere crevices) in which th6 sexes are 

 quite differently coloured, and which therefore form excep- 

 tions to the general plan. These are the Redstart and the 

 Pied Flycatcher. I am not sure how these exceptions 

 should be explained. But both these birds differ from all 

 the instances in 'which the tw^o sexes are alike and showy 

 in the additional fact that their bills are soft and weak, 

 and either of them would, therefore, probably make but a 

 poor fight against any other species that tried to oust it 

 from its nesting-hole. The fact of their martial prowess 

 being so little worth advertising may, perhaps, explain why 

 these birds don't advertise it. I can't support my conjecture 

 here by any facts within my own experience — the birds 

 being practically strangers to Ireland. But on looking up 

 Mr. Kirkman's account of the Redstart in " The British 

 Bird-Book " (vol. i., p. 425) I find that, according to him, 

 its nests are very liable to invasion by Titmice and other 



