THE CUCKOO 475) 



from the contact as if, to use Mr. Hudson's expression, pricked by 

 hot needle* only by HO doing to make matters worse. 80 unendurable 

 does the irritation become, that it galvanises the cuckoo into a 

 convulsive alni>i -up. ni;itural energy, which gives it the strength 

 required to expel tin- canst- of its sullerina^ 



It will be observed that, according to this account, the egg or 

 nestling reaches the back as the purely mechanical result of the 

 cuckoo's efforts to escape. According to most accounts there is a 

 deliberate effort made to get the object into place (p. 475). The 

 difference is probably one of interpretation, Jenner and others see- 

 ing in the preliminary arm and body movements of the cuckoo a 

 meaning that they may not possess. 



That the nestling cuckoo should be more or less sensitive to 

 pressure is no doubt to be explained by the fact that it is in a nest 

 a l)oii t half the size of that which its parents would have built. That 

 the irritability should be most acute in the hollow of the back may be 

 explained by natural selection. Any nestling cuckoo that chanced 

 to be born with physical modifications tending to increase the 

 sensitiveness of the dorsal nerves would profit in the struggle for 

 existence by the fact that, more than its fellows, it would be stiniuJajte.d 

 to greater energy in its efforts at ejection, and would, therefore, : haye 



of gaining undivided |x>ssession of the nfcstj-'aiiti" 



a better chance of gaining undivided |x>ssession 

 hence undivided attention from its foster-jwrents. 



The sensitiveness of the depression in the back does not appear 

 to arise from the existence of the depression itself. If it did, one 

 would expect that the dates of the appearance and disappearance 

 of the depression would correspond with the beginning and end of 

 the period during which the nestling cuckoo showed signs of un- 

 easiness at the presence of objects in the nest The evidence on the 

 point is scanty, but, as far as it goes, does not point to any definite 

 correspondence. 



With respect to the first appearance of the depression, Mr. J. H. 

 <Jurriey notes iliat. in the case of one young cuckoo he observed, it 



