30 THE STORY OF BIRD-LIFE. 



— which it must be mentioned, are in their turn 

 obliged to adopt a similar change that they may- 

 creep up unawares. Thus under the spur of 

 hunger is the evolution of the species involved 

 in this competition, furthered ; by means of this 

 system of interaction one upon another, does each 

 become more and more specialised, and at the 

 same time nearer and nearer the day of its ex- 

 tinction, which must arrive so soon as one of 

 the two competitors fails to respond to further 

 stimuli. We have a similar object lesson in 

 evolution enacted before us in the growth of 

 modern warfare. Compare the modern battle- 

 ship with the old three-decker. The iron vessel 

 which may be likened to the defenceless prey, 

 was the outgrowth of a need to resist more power- 

 ful guns — the tyj^e of the prowling carnivore — 

 and ships and guns have been competing for the 

 supremacy ever since, and the end is not yet. 



Some birds, however, adopt protective coloura- 

 tion which is not seasonal, but permanent. 

 Strange as it may seem, some of these are 

 amongst what would appear to be, the most 

 conspicuously coloured of birds. Take the case 

 of the hoopoe. This is an occasional visitor to 

 Britain — and would probably become resident 

 were it not so ruthlessly shot down on its every 

 appearance in this country. It is of a rich buff, 

 or sand colour, with a very large and beautiful 

 crest on the crown of the head, and the wings 

 conspicuously barred with black and white. 

 Yet, on the approach of a hawk or other 

 enemy, it throws itself flat on the ground, 

 drops its crest, and spreads out its wings and 



