34 PHILOSOPHY OF ZOOLOGY. 



shores during the winter, and joins those which have re- 

 mained there during the breeding season. The black head- 

 ed gull breeds both in England and Scotland ; but it re- 

 tires from the last mentioned country, while it continues re- 

 sident in the former. 



From the examples quoted, it appears that some birds, 

 which are stationary in one district, are migratory in ano- 

 ther. But that which chiefly merits our consideration is 

 the circumstance of those birds, whose annual migrations 

 are confined to our own shores, forsaking the high grounds 

 on the decline of summer, and seeking for protection at 

 a lower level, and in a warmer situation. When these mi- 

 grations become more extensive, the bleak moors and shores 

 of Scotland are exchanged for the warmer and more ge- 

 nial climate of England. Hence it happens, that some of 

 our Scottish summer visitants come from England, while 

 some of the English winter visitants come from Scotland ; 

 the summer birds of passage coming from the south, and 

 the winter passengers from the north. Do those birds 

 that perform more extensive migrations obey the same laws? 



As the summer birds of passage are more interesting 

 to us, since they perform the great work of incubation 

 in our country, than the winter birds of passage, which 

 are the harbingers of storms and cold, and only wait 

 the return of spring to take their leave of us, we shall 

 endeavour to find out the winter residence of the for- 

 mer, before we attempt to discover the summer haunts 

 of the latter. Natural history, it is true, is still in too 

 imperfect a state, to enable us to point out with certainty 

 the retreats of all those birds which visit us during 

 summer. But enough appears to be known to enable 

 us to ascertain the laws by which these migrations are 

 regulated in a number of birds ; and as the points of re- 

 semblance in the movements of the whole are nume- 



