118 HABITS OF BIRDS. 



accidentally precipitated, as we have seen happen, 

 from the rocks above. On the departure of their 

 enemy, the sheep began to feed again, but warily at 

 first, raising their heads at intervals to assure them- 

 selves that be was really gone ; while, to render as- 

 surance doubly sure, their leader again took his sta- 

 tion as sentinel for the common weal. 



Now we are disposed to conclude, that these two 

 cases of the sheep and the raven may, so far as food 

 is concerned, be taken as the general conditions of 

 the solitary and gregarious habits of birds. One 

 whose food is confined to living prey will prowl 

 alone, because along with associates he might fare 

 scantily ; while those who feed on seeds and other 

 vegetable substances, easily obtained in abundance, 

 congregate that they may feed more safely, by ap- 

 pointing, as the mountain sheep do, a sentinel to 

 warn them of danger. The raven, indeed, can hard- 

 ly be looked upon as subsisting wholly on living 

 prey. It is not furnished by nature with suffi- 

 ciently formidable weapons for this purpose ; and 

 almost uniformly, when carrion cannot be obtain- 

 ed, it attacks lambs, sickly sheep, or such as have 

 fallen into a ditch or bog, perching on the head 

 and pecking out the eyes. In temperate climates, 

 birds that prey on carrion are less necessary as 

 scavengers than in tropical countries, where flocks 

 of vultures collect together from distances that 

 have astonished all observers by whom the circum- 

 stance is recorded. The gregariousness of these 

 birds, however, may be plausibly referred to the 

 wise care of Providence to have offensive car- 

 casses speedily removed ; and it is manifestly 

 with this design that such birds are endowed with 

 extremely acute senses, either of vision or of smell, 

 probably both, so as to enable them to discover car- 

 rion afar off. 



This is well exemplified in two species, which 

 have been frequently confounded, the Turkey buz- 



