204 BRITISH LAND BIRDS. 



the secresy of their departure and the suddenness 

 of their reappearance have involved the matter 

 generally in great difficulties. As to the causes 

 that induce this habit we are much in the dark ; 

 there are two principal ones usually assigned, 

 namely, the want of food, and the want of a proper 

 temperature of air and convenient places for the 

 great work of breeding and rearing their young. 

 But though these reasons undoubtedly operate to a 

 large extent, they will not be found to hold good 

 in every instance, when closely inquired into. 



Then, as to the manner in which these surpri- 

 singly long journeys are performed, we may ask 

 many questions which we cannot answer. We do 

 not know by what means they subsist during the 

 period so occupied, nor can we tell why it is that 

 in the case of our summer migrants, the males 

 always precede the other sex in their time of 

 arrival. In short, after all our inquiries into this 

 branch of natural economy, much yet remains to 

 be learned, and we may say, with that delightful 

 naturalist Mr. White, that " whilst we observe 

 with delight with how much ardour and punctual- 

 ity these little birds obey the strong impulse im- 

 printed on their minds by their great Creator, it 

 is with no small degree of mortification we reflect 

 that, after all our pains and inquiries, we are not 

 yet quite certain to what regions they do migrate, 



