20 THE MIGRATIONS OF BIRDS 



There may be mentioned here also a transmuta- 

 tion theory held in early centuries which supposed 

 the change of one species to another at the coming of 

 cold and the assumption of proper form with return 

 of summer. This again may be traced to Aristotle, 

 who propounded the belief that the redbreast, or 

 European robin, changed to the redstart, a species of 

 similar size but different color, since the latter was 

 present in winter and the former in summer. Simi- 

 larly he informs us that the beccafico^ possibly the 

 garden warbler, became the blackcap, a related 

 species, and that at the proper seasons birds in 

 transition between the two could be observed. 

 Pliny repeated these tales, and later in popular be- 

 lief they were still further embroidered by the al- 

 leged transformation of certain marsh birds to 

 frogs. In our own country this shift from warm- 

 blooded bird to cold-blooded amphibian has been 

 attributed in many quarters to the sora rail, which 

 migrates by night so that its departure is unseen. 



All these beliefs, which seem strange and curious 

 to modern vision, arose in the attempt of the human 

 mind to explain observations which demonstrated 

 conclusively that many birds were present one day 

 and had vanished on the one that followed, while 

 their return came in a fashion equally mysterious. 

 With recognition of nocturnal flight as fact, such 

 stories lost credence immediately, save in the case of 



