Letters on Natural History. 5039 



vailed among our British songsters. This is the sum of my personal 

 knowledge of the bird; but I am going up to Oxford next month to 

 take my M.A. degree, and thence to visit a friend in the neighbour- 

 hood, whose diligence of research and observation in almost every 

 branch of Zoology are almost unrivalled, and fro«i him I doubt not I 

 shall be able to get you something more respecting the bird in ques- 

 tion, which 1 know is found in his neighbourhood. I am thinking of 

 getting a good air-gun cane: I had the loan of one a short time 

 since, and found it very useful for getting small birds, without the 

 noise and eclat of blazing away at their poor little carcases with 

 powder and shot. 



" I have not seen any swallows or martins since the general migra- 

 tion ; but I think that the account I gave you in my last, of the four 

 swallows in the roof of the Kildare-street Museum, tends to prove 

 that they may hybernate without becoming torpid ; though I cannot 

 agree with you in considering the winter torpor of the bat tribes as 

 an analogous case, since the much higher temperature of the blood 

 and greater rapidity of circulation in birds must act as a preventive to 

 torpor in a much higher degree than the lower temperature of quad- 

 rupeds ; though at the same time 1 believe it is now nearly ascertained, 

 however anomalous it may appear, that the cuckoo hybernates here, 

 buried in dry leaves and moss : I am told by a gentleman in this 

 neighbourhood that several are annually found by the gamekeepers in 

 that state, at the roots of furze-bushes on Millborongh Common. T 

 have lately found, among my bird-skins, one which appears beyond 

 doubt to be the female American swallow, respecting which I men- 

 tioned my suspicions in my last. 1 have now no doubt in my own 

 mind of the frequent British occurrence of that species, but shall not 

 make it public till I have the opportunity next summer of procuring 

 specimens of it and the common species for comparison, and of as- 

 certaining whether the difference mentioned by Wilson of the place 

 of nidification holds good in England : its breeding in barns and 

 outhouses in America may perhaps arise from there being, in many 

 parts of the United States, no chimneys for it to breed in, the most 

 cogent of all reasons against it ' I guess.' 



u Of the chiff-chaff and willow wren being specifically distinct I 

 have no doubt, as I know them both well ; but it is very difficult to 

 make out anything respecting them from books, from the great entan- 

 glement of their synonymy. I do not think the synonyms which 

 Rennie, in his edition of Montagu, quotes from Temminck, for the 

 willow wrens and fauvettes, are often right. Do you know which of 



