Bh-ds have a Leader. 153 



a reason why many species of birds are gregarious. 

 The apparently' defenceless martins and swallows in 

 this way dwell in some amount of security. If a 

 hawk comes near the sand quarry (or the house — 

 in the case of swallows) they all join together and 

 pursue him, twittering angrily, and as a matter of 

 fact generally succeed in sending him about his busi- 

 ness. Even those birds which do not build in close 

 contiguity no sooner find that a hawk is near than 

 they rise simultaneously and follow and annoy Mm : 

 so much so that he will sometimes actually drop the 

 prey he has captured. It is astonishing with what 

 temerit}' small birds, emboldened by numbers — 

 chaffinches, finches generally, sparrows, swallows, 

 and so on — will attack a hawk. 



The '■ quar-martins ' that came to the orchard wall 

 — emigrating from the quarry, and wandering about 

 in search of a suitable habitation — if young birds, as 

 we have supposed them to be, would naturally not yet 

 have had much experience, and so might think the 

 steep wall (roughly resembling the face of a quarry) 

 available for their purpose till they had made the ex- 

 periment. I have thought, from watching the motions 

 of birds that go in flights, that most of them have a 

 kind of leader or chief. They do not yield any thing 

 like the same obedience or reverence to the chief as 

 the bees do to the queen-bee, and exhibit little traces 

 of following his motions implicitly. He is more like 

 the president of a republic ; each member is individ- 

 ually free, and twitters his or her mind just as he or 

 she likes. But it seems to be reserved to one bird to 

 give the signal for all to move. So these martins, 

 after lingering about the wall for hours — some of 



