120 NUMERICAL RATIO. 



tain species respectively in their favourite locali- 

 ties, where they are sometimes seen in swarms, 

 cannot but be a matter of surprise. But this 

 surprise will be diminished when we reflect that, 

 whatever natural enemies these birds may have, 

 their aerial dexterity, and their rapidity of flight, 

 conjoined with a prompt and pugnacious spirit, 

 render them secure from the attacks of birds of 

 prey, of -predatory quadrupeds, or of snakes. 

 Man is their great destroyer, as a splendid ca- 

 binet of these birds will strongly enforce upon 

 the mind. In fact, the Humming-bird is safe 

 from the Hawk, and, as it never descends to the- 

 ground,* from every creeping thing ; it is, in- 

 deed, inclined to presume upon its powers of 

 wing, it gives chase to the Tyrant Flycatcher, 

 and hurries the Blue-bird and the Martin to 

 their boxes. Hence, though man may occasion- 

 ally thin its numbers, these are not so decidedly 

 diminished as would be the case if it were ob- 

 noxious to destruction from the assaults of many 

 predatory creatures. Again, the small size of 

 the nests, though these are large compared with 

 the bulk of the bird, the situations generally 



* We must here except the CRIMSON-THROATED HUM- 

 MING-BIRD ; Bullock found it on the mountains which en- 

 close the valley of Tenochtitlan, and observes, that he never 

 met with it but in high, cold situations; and that he several 

 times shot it on the gwund, on which the other species sel- 

 dom, if ever, alight. See " Six Months in Mexico," vol. ii. 

 p. 175. 



