MIGRATION. 279 



CHAPTER XXII. 



MIGRATION OF BIRDS. 



FEW subjects connected with natural history are 

 more interesting, or have more attracted the atten- 

 tion of ordinary observers, than the periodical ap- 

 pearance and disappearance of certain species of 

 birds. These curious phenomena have been no- 

 ticed in all ages and countries ; the sages of old, as 

 well as the scientific of our own days, have looked 

 upon them with interest ; and to the agriculturist, 

 the shepherd, and all whose occupations lead them 

 to the fields, the woods, or the hills, they are in 

 some measure familiar. Even the inspired seer 

 has found in them an illustration suited to his pur- 

 pose : " The stork in the heaven," says the prophet 

 Jeremiah, "knoweth her appointed times; and the 

 turtle, and the crane, and the swallow observe the 

 'time of their coming." 



The regular appearance and disappearance of 

 some species of birds excited the curiosity of ob- 

 servers in all ages, and led to many conjectures re- 

 specting its causes. It was long alleged and be- 

 lieved that swallows, instead of removing to warmer 

 climates, lie concealed in fissures of rocks, in sand- 

 banks, in the holes of decayed trees, and even at 

 the bottom of the water in ponds, remaining during 

 the winter in a torpid state. " It is certain," says 

 the Dutch naturalist Jonston, " that in hollow trees, 

 lying many close together, they preserve them- 

 selves by mutual heat." " In certain woods of Up- 

 per Germany," says the author of the Physicae 

 Curiosae, " upon cutting up a rotten oak-tree, it has 

 been found full of swallows." He does not quote 



