A close look at an Oriental Pied Hornbill

posted in: Hornbills, Morphology-Develop. | 0

Kennie Pan’s close-up study of the Oriental Pied Hornbill (Anthracoceros albirostris) provides an opportunity to examine the details of the hornbill’s head (above).

The black head has bluish-white facial markings – bare circumorbital (meaning around the eye) skin and bare throat patch. The eyes are dark red in the male and browner in the female (not too obvious in the image). A prominent feature is the long, sweeping eyelashes.

The pale yellow, down-curving bill has black markings, with the lower mandible having a black base. Although the large bill appears clumsy, it can be used with surprising dexterity, like delicately picking up a small fig, an insect or even a bird’s egg. At the same time it can be used as a pickaxe to knock off reasonably sized living creatures. The force of the mandibles can be strong indeed, to crush the skulls of small animals and seeds or to dig the ground to collect soil (left). The serrations along the edge of the mandibles allow for better grip of fruits or to grip the fruits to soften them before swallowing. The exceptionally length of the bill allows the hornbill to reach for food in areas that do not support the weight of its body.

At the top of the bill is a large casque, a structure unique to hornbills. It is a hollow structure, supported internally by bony ridges and rods, possibly with some opening to the mouth. This allows it to act as a resonating chamber, thus the loud nasal calls.

The casque here runs to slightly more than half the length of the bill. The male has a larger casque that tapers forward (above). In the female the casque is smaller and blunt at the tip (top). It similarly has black markings towards the front end.

The image on the right clearly shows the asymmetrical wing feathers – stiff feathers with a central shaft, a broad inner vane and a narrower outer vane. They form the predominant wind-catching part of the wing. Note that the dark feathers are white-tipped and free from wear and tear. Above the wing feathers are the rows of coverts, smaller feathers that overlap the flight feathers at their bases.

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