MIGRATION. 275 



the former, and from the north in the latter season. 

 The Bermudas are said to lie six hundred miles from 

 the nearest part of the continent. This seems an ex- 

 traordinary flight for so small a bird ; but it is a fact 

 that it is performed. If we suppose the blue-bird to 

 fly only at the rate of a mile a minute, which is less 

 than I have actually ascertained them to do overland, 

 ten or twelve hours would be sufficient to accomplish 

 the journey." Such facts as this seerns to render 

 quite unnecessary the admission of Catesby, who, 

 while he believed, for himself, that birds were capable 

 of very long 1 flights over the sea, allowed that they 

 might be guided, by the same sagacity which instructs 

 them to change climates, " to the narrowest part of 

 our channel, to evade the danger of passing a wide 

 sea." We doubt not that even the short-winged 

 quails, of which he is particularly speaking, would 

 scorn to be confined to the passage between Dover 

 and Calais. 



The periodical migration of the gannet affords an 

 instance of a mixed nature. That bird arrives early 

 in spring, and is located in four or five spots along 

 the British coasts, of which may be mentioned the 

 Bass Rock, Ailsa Craig, and St. Kilda. In autumn 

 the gannets leave their breeding places, and are seen 

 along the coasts of England, and in the channel. 

 In mild winters some individuals often remain, and 

 even the whole flock has been known to winter in 

 their summer residence. Even when they all leave 

 the breeding places, many individuals do not extend 

 their migration beyond the southern coasts of Eng- 

 land, but where the extreme point of the range may 

 be has not yet been ascertained. 



In all these cases, the distribution of food seems 

 to be the principal cause of the movements of the 

 birds ; but in other cases it is clear that the rigour of 

 the winter also acts as an exciting cause ; yet it is 



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