296 SCIENCE OF AGRICULTURE. Part IT. 



of the more obvious instances of these changes, in British species, may be here pro- 

 duced. 



1968. The alpine hare is a very remarkable example. Its summer dress on the Grampian mountains 

 is a tawney grey ; but in winter it is a snowy white. The hair of the ermine is of a pale reddish brown 

 during summer ; in harvest it becomes clouded with pale yellow : and in November is of a snow-white 

 color. There are many examples of changes in the color of the clothing in the feathered tribe. The white 

 grous or ptarmigan is of an ash color in summer, and fine white in winter. The black guillemot ( Una 

 grylle) is of a sooty black during summer ; during winter its plumage is clouded with ash colored spots on 

 a white ground. This change of color in the dress of animals seems intended to regulate their temperature 

 by the radiation or absorption of caloric : a black animal will give out its heat by radiation much slower 

 than one in a white clothing. 



1 969. The migration of animals is another circumstance affecting their distribution. 

 Quadrupeds make only partial migrations ; as the stag and the roe from the mountains 

 to the plains. The winged and finned quadrupeds migrate more extensively, as the 

 great bat which inhabits England during summer, and spends its winters in a torpid 

 state in Italy: and the Greenland seal, which migrates southwards to Ireland in 

 winter. 



1970. The migrations of the feathered tribe are the most numerous ; but 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. Migrating birds are either summer birds of passage, which arrive in 

 this country in spring : or winter birds of passage, which arrive in autumn and depart in spring. 



1971. The summer birds of passage are, among water birds, the terns and gulls ; among land birds, the 

 swallow, quail, turtle dove, &c. The winter birds of passage chiefly belong to the tribe of water fowls. 

 The swallow, about whose migrations so many idle stories nave been propagated and believed, departs 

 from Scotland about the end of September, and from England about the middle of October. In the latter 

 month M. Adanson observed them on the shores of Africa after their migrations from Europe. He in- 

 forms us, however, that they do not build their nests in that country, but only come to spend the winter. 

 M. Prelong has not only confirmed the observations of Adanson, in reference to swallows, but has stated, 

 at the same time, that the yellow and grey wag-tails visit Senegal at the beginning of winter. The former 

 (Motacilla flava) is well known as one of our summer visitants. The nightingale departs from England 

 about the beginning of October, and from the other parts of Europe about the same period. During the 

 winter season it is found in abundance in Lower Egypt, among the thickest coverts, in different parts of 

 the Delta. Those birds do not breed in that country, and to the inhabitants are merely winter birds of 

 passage. They arrive in autumn and depart in spring, and at the time of migration are plentiful iii the 

 islands of the Archipelago. The quail is another of our summer guests, which has been traced in 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 re-visit in their migrations the shores 

 of the Mediterranean, Sicily, and the islands of the Archipelago. While these birds perform those ex- 

 tensive 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 Andalusia during the 

 winter season, and return to us in the spring. 



1972. Our summer birds of passage, thus appear to come to us from southern 

 countries, and, after remaining during the warm season, return again to milder re- 

 gions. A few of our summer visitants may winter in Spain or Portugal ; but it 

 appears that in general they migrate to Africa, that unexplored country possessing every 

 variety of surface, and consequently great diversity of climate. It is true that we are 

 unacquainted with the winter retreats of many of our summer 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 operations which they perform 

 during their residence with us are also similar, we have a right to conclude that they are 

 subject 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. 



1973. J/^roo/ of the accuracy of the preceding conclusion, we may observe that it is a fact generally 

 acknowledged, that the summer birds of passage visit the southern parts of the country a few days, or 

 even weeks, before they make their appearance in the northern districts. Thus, the common swallow 

 {Hirundo rustica,) appears in Sussex about the beginning of the third week of April ; while in the neigh- 

 borhood of Edinburgh it is seldom seen before the first of May. The cuckoo appears in the same 

 district about the last week of April; in Edinburgh seldom before the second week of May. The 

 reverse of this holds true with these summer visitants at their departure. Thus dotterells {Charadrius 

 nwrinellus) forsake the Grampians about the beginning of August, and Scotland by the end of that month ; 

 while they return to England in September, and remain there even until November. A difference of 

 nearly a month takes place between the departure of the goatsucker (Caprimulgus Europceus) from 

 Scotland and from the south of England. 



1974. The torpidity or fiT/bernaiion of animals, is evidently designed to afford pro- 

 tection against the cold of winter. There are several quadrupeds which become torpid, 

 as the bat, hedgehog, marmot, hamster, dormouse, &c. The torpid animals of Britain 

 usually retire in October, and re-appear in April. Previous to their entrance into this 

 state of lethargy, these animals select a proper place, in general assume a particular 

 position, and even in some cases provide a small stock of iood. 



1975. All the torpid animals retire to a place of safety, where, .at a distance from their enemies, and 

 protected as much as possible from the vicissitudes of temperatures, they may sleep out, undisturbed, 

 the destined period of their slumbers. The bat retires to the roof of gloomy caves, or to the old chim- 

 neys of uninhabited castles. The hedgehog wraps itself up in those leaves of which it composes its 

 nest, and remains at ;the bottom of the hedge, or under the covert of the furze, which screened it, 

 during summer, from the scorching sun or the passing storm. The marmot and the hamster retire to 

 their subterranean retreats, and when they feel the first approach of the torpid state, shut the passages to 

 their habitations in such a manner, that it is more easy to dig up the earth any where else, than in such 



