30 PHILOSOPHY OF ZOOLOGY. 



The systematical naturalists have likewise collected many 

 scattered observations, and the subject appears now to be 

 capable of receiving a satisfactory illustration. It is not 

 our intention to enter into any minuteness of detail, regard- 

 ing the migrations of particular species, but to ascertain the 

 laws of migration, and the circumstances under which it 

 takes place. 



Before entering farther upon the subject, it may be pro- 

 per to state, that the same species which is migratory in 

 one country, is in some cases stationary in another; as the 

 linnet, which is migratory in Greenland, but stationary in 

 Britain. In Britain, both male and female chaffinches are 

 stationary, while in Sweden, the latter are migratory *. 

 Some species of the same natural genus are migratory, while 

 others are stationary. Thus the fieldfare is migratory, 

 while the blackbird is permanently resident. 



Migrating birds may be divided into two classes, from 

 the different seasons of the year in which they arrive or de- 

 part. To the first class will belong those birds which ar- 

 rive in this country in the spring, and depart from it in au- 

 tvmin, and are termed Summer Birds of Passage. The 

 second will include those which arrive in autumn, and de- 

 part in spring, and are called Winter Birds of Passage. 



The Summer Birds of Passage are not confined to 

 any particular order or tribe ; nor are they distinguished 



• EcKMARK, when speaking of the migrations of this bird, informs us, 

 " Mares inter primas sunt aviculas, quae sonum suum hieme usitatum in 

 cantum vertunt jucundissimum : vere primo, sub initium mensis regelationis, 

 arboribus ad pagos insidentes gaiiuli, fxminis adhuc absentibus, ver indicant 

 adstans. Redeuntibus denique turmis maximis, quae ccelum fere abscondunt, 

 fceminin, omnes conjugcs requirunt, quibus conjuncti sylvas petunt, ibi ut 

 nidulos construant et multiplicentur. Initio mensis defoliationis marcs suos, 

 apud nos remanentes,_/(E7nJn<E deserunt mutabiles, solse regiones petentes 

 pevegrinas." Amaen. Acad, iv: 595. 



