12 
BIRD-LIFE. 
birds of prey is so powerful that they can even rapidly 
digest old bones, as do the Vultures. Birds feeding 
on seeds require other means of digestion beyond those 
afforded by the chemical working of the crop and the 
juices of the stomach; these are supplied by purely 
mechanical means, which bruise the grain by the help 
of sand and small stones which they swallow; all such 
birds whose food contains in itself the means of grinding, 
do not do so; as, for example, those feeding on shell¬ 
fish or snails. Indigestible materials, such as hair, 
feathers, scales, &c., are thrown up by flesh- and insect¬ 
eating birds (Owls, Goatsuckers, &c.) in dry round or 
oblong pellets, called “ castings.” Immediately the crop 
is empty the bird begins to feed again, and, indeed, 
sometimes, though it is quite full at the time, the creature 
will still continue to feed, should it come across some¬ 
thing more to its taste than what it has already enjoyed. 
After a long fast it is astonishing the amount that a bird 
will devour; though it is not a question of a surfeit, still, 
after an unusual feast, its precautions for personal safety 
are sometimes forgotten during the after-dinner sleep: 
birds of prey have been caught napping, more than once, 
with the hand, while enjoying their “ forty winks.” 
Many flesh-feeders, like the Marabou Stork (. Leptoptilus ), 
are so greedy as to, though mortally wounded, hastily 
devour anything thrown to them. Others, again, will 
starve rather than touch even their natural food when 
offered them in captivity or under adverse circumstances. 
Birds, as well as all other animals, become fat or lean, 
according to the quantity and quality of the food they 
obtain: emaciation, however, does not take place so 
rapidly as one would imagine, for many birds are able to 
do without food for days, and even weeks, together. The 
