ANATOMY OF BIRDS
GEOGRAPHICAL DISTRIBUTION
MIGRATIONS OF BIRDS
CLASSIFICATION OF BIRDS
LIZARD-TAILED BIRD
AMERICAN TOOTHED-BIRDS
THE OSTRICHES
THE RHEAS
EMEUS AND CASSOWARIES
THE TINAMOUS
THE KIWIS
THE PENGUINS
LOONS AND GREBES
ALBATROSSES & PETRELS
STORK-LIKE BIRDS
GOOSE-LIKE BIRDS
FALCON-LIKE BIRDS
FOWL-LIKE BIRDS
CRANE-LIKE BIRDS
PLOVER-LIKE BIRDS
CUCKOO-LIKE BIRDS
THE ROLLER-LIKE BIRDS
SPARROW-LIKE BIRDS
Birds and Birding's Guide to:
Watching THE ROLLER-LIKE BIRDS
THE ROLLERS AND THEIR ALLIES
THE HORNBILLS
THE HORNBILLS beak Structure
The Hornbills are mostly birds of large size, several exceeding four feet in length, and few falling under two feet. They are chiefly remarkable for the large, often very large, bill which is surmounted in many species by a casque, which may itself be so large as to appear like a second bill above the other, while in other forms it is quite rudimentary or even reduced to a mere keel.
The bill and casque, in all but one of the Hornbills, is hollow with quite thin walls and supported inside by a cancellated bony structure. In the Solid-casqued Hornbill (Rhinoplax), as the name implies, the whole of the anterior wall is solid. In a majority of forms the casque is closed, the exception being in the Ground Hornbills (Bucorax), in which it is more or less open in front, giving them a very peculiar appearance. Structurally the Hornbills have the palate of the bridged (desmognathous) type, no basipterygoid processes or cstca,, while the breast-bone is broad behind and provided with two notches as in the Hoopoes; the whole skeleton is unusually pneumatic.
Among other more or less important characters it may be mentioned that they have well-developed eyelashes, a feature not common among'birds, usually large, powerful wings, and a tail of ten feathers, the central pair of feathers being in some cases much longer than the others.
The wings are further peculiar in that the under coverts do not cover the basal parts of the quills, and it has been suggested that it is the air rushing between the bases of the quills that produces the loud sound heard when they are in flight, a noise that has been likened to a railway train at a little distance.
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