THE ROOK AND JACKDAW 33 



selves as far as ever from the true solution. All that can with any 

 certainty be said is that the bare face of the rook, like the blue eye of 

 the jay or the red breast of the robin, marks the advent of maturity. 

 Why the rook should have to be content with a rough unfeathered 

 face instead of a bright blue eye or a ruddy waistcoat is a question 

 that science has still to answer. 



If we turn from the bare patch round the base of the beak to 

 the beak itself, we find an instrument that, in comparison with the 

 bludgeon-like bill of the raven and crows, is certainly well adapted 

 for probing the soil (cf. Figs. 1 and 2 in the Classified Notes). In 

 this case we are generally content with the Darwinian view that 

 the modification has been the result of natural selection, a view 

 that does not, of course, explain how the variation arose, but only 

 why it persisted. It did so, presumably, because the rooks that, 

 owing to some cause unknown, happened to be born with a 

 beak somewhat longer than their fellows thereby gained a distinct 

 advantage in the search for food. Being better nourished, and con- 

 sequently stronger than the shorter-beaked individuals, they had a 

 better chance of surviving in the struggle for existence, and hence 

 of perpetuating in their offspring an advantage secured, it may be 

 observed, by no merit of their own. Perhaps the bare patch has 

 arisen in the same way, though, except as a mark of recognition and 

 maturity, its utility to the species is not apparent 



It is a common opinion that when rooks are feeding in a field 

 they post sentinels. That they frequently take no such precaution, 

 even when there are hedges covering the approach to the field on 

 which the flock has pitched, is a fact that can easily be verified. 

 Further, it is not safe to assume that the birds sometimes seen 

 perched on trees near by where the flock is feeding, are there for 

 the express purpose of keeping watch ; they may simply be resting. 

 Their elevated position would, of course, enable them to mark and 

 signal the approach of danger sooner than their fellows on the 

 ground, and thus give them the appearance of being sentinels. 



B 



