Cases Unexplained. 77 



bird was a sparrow-hawk, a species that is sometimes 

 mistaken for the cuckoo." 



But in the case of a bird where the migratory in- 

 stinct is so strong, and in any case where this instinct 

 failed to act, some reason must be found in the ex- 

 ceptional physical condition of the bird which led it 

 to brave the rigours of winter here instead of to 

 attempt migration — some defect of wing feathers or 

 power of flight. The food element is in all such 

 questions a most important one. 



This would account for what we are constantly 

 hearing of the cries of cuckoos at dates so early that 

 no ornithologist can believe that cuckoos had then 

 returned from migration. Other cases there are an- 

 alogous and at present wholly unexplained. There 

 is, for example, that of the corncrake, or landrail, 

 where, considering the defect of wing-strength, the 

 persistent migration is wonderful, and the instinct to 

 it is as powerful in view of its drawbacks as in any 

 bird ; yet in many districts landrails remain and skulk 

 about here through the winter, and of this we know a 

 case the year before last in Essex. 



^N?/", 



