30 TROPIC DAYS 



four, and then twent}' nests, all containing eggs or 

 helpless young. By these and similar mishaps during i 

 the season the colony suffered loss to the extent of at 



least a hundred. 



"But, like the martlet, 

 Builds in the weather on the outward wall 

 Even in the force and road of casualty." 



How often, too, do we find nests in places absurdly 

 wrong ? Wonderfull}' and skilfully constructed nests 

 are attached to supports obviously weak, and eggs are 

 laid on the ground right in the track of man and less 

 considerate animals. Some birds seem to lay eggs and 

 rear young solel}'- that snakes may not lack and suffer 

 hunger, while how large a proportion of beautiful and 

 innocent creatures are destined to become prey to 

 hawks ? 



Years ago scientific visitors to a coral islet found 

 almost innumerable sea birds and eggs. The multitude 

 of birds and their prodigious fecundity inspired the 

 thought that the "rookery" for the whole breadth of 

 the Indian Ocean had been discovered. Investiga- 

 tions showed that the islet was also the abiding-place 

 of a certain species of lizard which subsisted entirely 

 on eggs. It was calculated that not one egg in several 

 hundred was hatched out ; yet in spite of such an extra- 

 ordinary natural check the islet was enormously over- 

 populated. Thousands of birds every year laid eggs 

 for the maintenance of fat and pompous reptiles, with- 

 out reflecting that there were other and lizardless isles 

 on which the vital function of incubation might be 

 performed without loss. Years after other men of 

 science sought the isle. Birds seemed to be as numerous 

 as ever, but the lizards had disappeared. Had the 

 birds been wise enough to perceive that the plague 

 of lizards had been sent as reproof for overcrowding, 



