CUCKOOS 65 



crows have returned, but every now and then she 

 is caught in the act and driven off like her husband, 

 uttering volleys of shrill outcries. 



The extreme differences between the plumage 

 of the cock and that of the hen in this case leave 

 no room for doubt as to the part that each sex 

 plays in accomplishing their felonious purpose ; 

 that of the male being clearly to distract attention 

 by his conspicuous appearance and imperative out- 

 cry, and that of the female to utilise her sober 

 colouring as a means of lying hidden until she sees 

 a favourable chance for invading the coveted nest. 

 They certainly serve to show very clearly how 

 efficiently the insistent cry of the male makes for 

 the successful conduct of the nefarious schemes of 

 his wife. Had such differences in sexual plumage 

 been normal to cuckoos as a group, no debate could 

 ever have arisen as to the limitation of the charac- 

 teristic call to the male sex. But it can hardly be 

 supposed that they have arisen in this case merely 

 in order to afford a clue for the solution of an 

 ornithological problem, and, hence, some other and 

 more satisfactory explanation of their origin must 

 be looked for. It may possibly be found in the 

 exceptional difficulties that the species has to 

 encounter in successfully foisting off its eggs upon 

 foster-parents of great strength and high intellectual 

 endowment. Crows are not only formidable 

 enemies when provoked, but are also exceptionally 



