LONG I- ARK l>, SHORTEARED, AND TAWNY-OWIB 407 



i li< ii enemies, or from Mi unuHual succession of yean of plenty, voles 

 (JHicrotot agmtu) increase in such numbers as to become a plague in 

 the land, when, it would seem, numbers of the birds which would 

 otherwise have passed northwards in the spring to their usual l>n-. .1 

 ing haunts remain \\itli us, tempted by the abundance of food concen- 

 trated in tin- infrMrd aiva>. Such \<lc plauurs. in tlu-sr islands, aiv 

 happily of infrequent occurrence, but records of such visitations 

 r\und back over more than three hundred years. Kent and Easel 

 u<re so stricken during 1680-81; Essex again in 1648; Hilgay, in 

 Norfolk, in 1754; and the south of Scotland and north of England in 

 1890-92. The alarming character of such outbreaks may be gathered 

 from the records of 1890-92, when all that human ingenuity could 

 Mi-u'rM |ir ( \-d nn;i\ailin-. In ><-lkirk>liiir Mnir thiitrni thoiixai.d 

 were killed in three months by men armed with wooden spades, and 

 in Glenkerry no less than fifteen thousand were killed in one month 

 by similar means. Meanwhile the owls and kestrels thronged to 

 the scene. The former displayed a remarkable fecundity under the 

 stimulus of this plenty. Normally laying from four to eight eggs, 

 clutches of thirteen now appeared, and at least two broods were 

 ivaivd ly tin- inajoritN of In-ceding birds. Thus. lrfoiv tin- rnd of tin- 

 plague, no less than four hundred pairs of shorteared-owls alone were 

 ti tiding sustenance in the stricken area. A small wood within the 

 *<tricken area is described as presenting a most remarkable appear- 

 ance, the ground being densely covered with the pellets ejected by 

 the owls, containing the bones and fur of the pests. 



This flocking of the owls, and their abnormal fecundity, furnishes 

 a most striking illustration of the way the balance of nature is main- 

 tained. Furthermore, it has an interesting sequel, which makes doubt 

 as to the sequence of events impossible. For when the voles became 

 reduced to their normal numbers, and no other source of food was 

 discovered as a substitute, the ranks of the owls became speedily re- 

 duced by starvation, and large numbers were picked up dead on the 

 former scenes of plenty. Many, doubtless, escaped by migration, and 



