152 BIRD HAUNTS AND NATURE MEMORIES 



would adjust its dislocated balance. And what would 

 happen, any time might happen, to the guillemot if the 

 carrion crow, jackdaw or other egg-snatching species 

 should for a few years increase abnormally ? Certainly 

 there would be a rapid depopulation of the crowded 

 ledges of our steepest maritime cliffs. 



Fluctuations do occur, sometimes through climatic 

 variation, oitten directly due to human stupidity, or from 

 reasons which we cannot fathom. Suddenly we awake 

 to the fact that the field vole is swarming in some hilly 

 area, that the concourse of starlings is beyond all calcula- 

 tion, that the gamma moth is on every plant, that an 

 army of caterpillars of the antler moth are eating all 

 before them. For two or three seasons the overabundance 

 continues, and we are threatened by a new plague of 

 Egypt. The last serious vole plague happened in Low- 

 land Scotland in 1889-90; grass and herbage were de- 

 voured, sheep were starved for want of nourishment. 

 Shepherds and farmers, unable to stop the increase of 

 the little mammal with dog, trap, and poison, appealed 

 pitifully for help, and a Parliamentary Committee was 

 appointed to enquire into the trouble. Some very inter- 

 esting zoological facts were ascertained; man rose in 

 arms against the rodent; many useless suggestions were 

 mooted, and still the voles increased. The Committee 

 laboured, sent a commission out to Greece to learn what 

 they did when voles troubled them, wrote a very instruc- 

 tive Blue book, and drew fees. But Nature could not 

 wait for Mediterranean steamers to return, and took the 

 matter in hand. Who can explain what happened ? 

 Short-eared owls came over in the autumn in greater 

 numbers than had ever previously been known, and fewer 

 returned across the North Sea in spring; they had hit on 

 a land of plenty, and they stopped. They nested and 

 reared double broods, laid larger clutches than usual, and 



