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1869.] HABITS OF THE HORNBILLS. 145 
the keepers and others who are known to him. The male Concave 
Hornbill (Buceros cavatus) now in the Gardens will frequently throw 
up grapes and, holding them in the point of the bill, thrust them 
into the mouth of the keeper if he is not on the alert to prevent or 
avoid this distinguished mark of his kinduess. 
We have now to consider the facts brought forward; and in no 
class of animals do we find so many instances of the frequent and 
easy mode of casting up or reproducing the food, or in other cases 
the indigestible substances taken with the food, asin Birds. But 
there is more than this to be noticed; for instance, im the Esculent 
Swallows. We know the so-called edible Swallow’s-nest consists 
of a gelatinous secretion from the glands of a kind of Swift; and 
doubtless a portion only is used to form the nest; the secretion is, 
in all probability, continued to feed the female and young, probably 
mixed with the insects captured during flight. There is also a 
similar secretion from the Woodpecker, but in this case made to 
assist in the capture of their food; and many other instances can, 
no doubt, be brought forward, showing the power that birds have 
of ridding their stomachs of that part of their food not required for 
their nourishment. One very remarkable instance I well remember. 
A year or two ago I found in my garden, in a small heap, about a 
handful of the most beautiful blue pills, about the size of peas and 
studded all over with brilliant and shining blue fragments. I soon 
discovered that they were the castings of the Flycatchers that had 
a nest immediately above the spot upon which I found them; the 
charming colour was due to the outer skins of the Bluebottle flies 
upon which the birds had fed. All the insect-feeding birds throw 
up pellets consisting of the refuse or indigestible parts of the insects 
they swallow, just in the same way as the Raptorial birds (as Hawks, 
Owls, &c.) cast up the feathers, bones, hair, and food of grain- 
eating animals in the form known as castings or pellets. 
In conclusion, I think I may fairly reason that it is much more 
likely that these food-pellets of the male Hornbill are intended for 
the support of the female and young, and belong to the natural and 
healthy condition of the birds which produce them, than that they are 
the result of indigestion or disease. For we see that the power and 
habit of casting up from the stomach is one of frequent and common 
occurrence among birds, and also find that the secretions of the 
cesophagus are used as food for the young of many species of birds : 
in the Parrots and Pigeons I think this is universal. 
Another strong argument in favour ef my belief is to be found in 
Dr. Livingstone’s statement that ‘the male bird by his constant 
attention upon the female becomes so prostrate and exhausted that 
a slight change in the temperature causes him to fall down and die.” 
It cannot be supposed that the mere collecting food for the female 
is the cause of this fatality ; it is doubtless the overtaxing the system 
by the constant secretion of this nutritive matter, reminding one of 
the blood in the nests of the Esculent Swifts after the birds have been 
robbed of the first and second nests. But the most positive proof 
of finding this package of food is given, without, however, under- 
Proc. Zoou. Soc.—1869, No. X. 
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