36 PHILOSOPHY OF ZOOLOGY. 



Africa. A few, indeed, brave the winters of England, and 

 in Portugal they appear to be stationary. But in general 

 they leave this country in autumn, and return in spring. 

 They migrate about the same time from the eastern parts 

 of the Continent of Europe, and visit and revisit in their 

 migrations the shores of the Mediterranean, Sicily, and the 

 islands of the Archipelago. 



While these birds perform those extensive migrations 

 which we have here mentioned, others are contented with 

 shorter journeys. Thus, the razor-billed auk (Alca torda), 

 and the puffin (Alca arctica), frequent the coast of Anda- 

 lusia during the winter season, and return to us in the 

 spring. 



These facts, and many others of a similar nature, which 

 might have been stated, enable us to draw the conclusion, 

 that our summer birds of passage come to us from south- 

 ern countries, and, after remaining during the warm sea- 

 son, return again to milder regions. A few of our sum- 

 mer visitants may winter in Spain or Portugal ; but it 

 appears that in general they migrate to Africa, that unex- 

 plored country possessing every variety of surface, and con- 

 sequently great diversity of climate. It is true that we are 

 unacquainted with the winter retreats of many of our sum- 

 mer birds of passage, particularly of small birds ; but as 

 these arrive and depart under similar circumstances with 

 those whose migrations are ascertained, and as the opera- 

 tions which they perform during their residence with us are 

 also similar, we have a right to conclude that they are sub- 

 ject to the same laws, and execute the same movements. 

 What gives weight to this opinion, is the absence of all 

 proof of a summer bird of passage retiring to the north 

 during the winter season. 



In proof of the accuracy of the preceding conclusion, we 

 may observe, that it is a fact generally acknowledged, that 



