THE SWALLOW TRIBE. 339 



far-seeing eye of one swallow discover the owl in 

 the air above him, and a piercing shriek will be 

 uttered, which will call up not only all the swallows 

 and martins about him, but will, as Mr. Knapp 

 observes, be instantly understood by every finch 

 and sparrow, and its warning attended to. " The 

 instant," says this \vriter, "the signal of danger 

 is uttered, we hear the whole flock, though composed 

 of various species, repeat a separate moan, and 

 away they all scuttle into the bushes for safety." 



But the habit of thus seeking shelter is not 

 invariable, for in some cases, when the swallow 

 shrieks its alarm, the whole tribe of swallows and 

 other small birds rush boldly to the scene of danger, 

 and they will sometimes with wing and beak attack 

 their formidable foe till some individual among them 

 falls a victim to its corn-age, and serves as a warning 

 to the others to quit the unequal combat. 



Although no other birds make quite so loud a 

 chattering as the swallow before migTating, yet 

 something similar is heard among other tribes when 

 preparing for their autumnal voyage. The causes 

 of migration are involved in mystery, though the 

 want of proper food and a presentiment of coming 

 cold, are probably the chief inducements. The 



