Dr. Jenner on the Migration of Birds. 53 



How the cuckoo, that disappears at so early and so hot a sea- 

 son as the first week in July, can become torpid, is beyond the 

 power of conception. 



The apparent incapability of the landrail to perform the 

 task of migration, has often been so strongly adduced as a 

 presumptive argument in favour of the hibernating system, 

 that those who do not admit that of migration, were it to re- 

 main unnoticed, might urge it as an objection. It must be ad- 

 mitted, that a superficial examination of the habits of this bird 

 tends to favour the supposition of its incapacity for so great an 

 exploit, as it often rises from the ground like an half-animated 

 lump, and seems with difficulty to take a flight of a hundred 

 yards ; but let us remark its powers when seriously alarmed. 

 Should it be forced upon the wing by any extraordinary cause, 

 by the pursuit of a hawk, for example, the velocity of its 

 flight, and the rapidity of its evolutions to avoid the common 

 enemy of its race, will at once appear. This is no very rare 

 exhibition. Necessity here, as in migration, becomes the pa- 

 rent of exertion, which, when thus called forth, cannot be 

 shown in a much gi'eater degree by any of the feathered tribe. 

 The moor-hen (which winters with us) gives another instance 

 of what a bird, which appears so much to want activity in its 

 ordinary flights, is capable of performing when exertion is ac- 

 tually required. When pursued by ahawk, and self-preservation 

 calls up all its powers, it may be seen to rush up into the air 

 with amazing velocity, almost as high as the eye can reach, 

 then darting down with an equal pace, it often, by such rapid 

 manoeuvres, escapes the destructive talons of its swift pursuer. 



It is a remarkable fact that the swallow tribe, and probably 

 many other birds which absent themselves at stated periods, 

 should return annually to the same spot to build their nests. 

 The swift, which for nine months has some distant region to 

 roam in, was selected for the purpose of an experiment to as- 

 certain this with precision. At a farm-house in this neigh- 

 bourhood I procured several swifts, and by taking off two 

 claws from the foot of twelve, I fixed upon them an indelible 

 mark. The year following their nesting places were exa- 

 mined in an evening when they had retired to roost, and there 

 I found several of the marked birds. The second and third 

 year a similar search was made, and did not fail to produce 

 some of those which were marked. I now ceased to make an 

 annual search ; but at the expiration of seven years, a cat was 

 seen to bring a bird into the farmer's kitchen, and this also 

 proved to be one of those marked for the experiment. 



That the bird, when the stimulus for migration is given, 

 with the choice before it of almost any part of Europe for its 



annual 



