#Rhinoceros hornbill toucan full#

Running along the top of the hornbill beak and often extending on to the skull roof is a hollow bony ridge or crest, sheathed in protective keratin. In some species, the female remains in the chamber for as long as five months. A slit remains the only point of contact with the outside world, and the female and chicks then rely on the male to collect and deliver food. Using mud and droppings, the female walls herself into the chamber. When the time comes to nest, the pair selects a cavity in a tree or rock face. Most species are monogamous and defend territories, but co-operative breeding is present in others. They are very noisy in flight, and the whooshing sound of their wing feathers means that they are sometimes heard before they are seen. Like most forest-dwelling birds, hornbills have broad, rounded wings. The long, thick eyelashes of some species help shield the eyes from sunlight. After grabbing a prey animal, a hornbill will often beat it to death against a perch. The hornbill palate is roofed with bone and is hence reinforced and strong compared to that of most other birds (Burton 1984). This is unusual among birds, as the bill tip is normally outside the bird's field of vision. It seems logical to assume that hornbills can see their own bill tip, and studies of their visual fields show that sophisticated binocular vision allows this (Martin & Coetzee 2004). This technique has been referred to as 'ballistic transport' (Baussart & Bels 2010) (the same feeding technique has been convergently evolved in toucans: this is all rather different from the 'catch and throw' technique practised by ratites and some other birds). Hornbills have a particularly short tongue that doesn't play a role in the manipulation of food items: once an object is positioned as desired at the jaw tips, it is thrown backwards into the throat. The birds use these to perform precise grasping actions, and they also manipulate objects before swallowing.

#Rhinoceros hornbill toucan full#

In many species, the tips of the upper and lower jaws are the only parts of the jaws that are in full contact.

Their size, large appetites and ability to range far and wide in search of fruit make hornbills important seed dispersers. Ground hornbills are able to subdue such large prey as snakes and rabbits. The majority of species use it to pick fruit and to grab small animals while foraging in trees, but some use it as a hammer to excavate bark or soil when searching for insects. This massive bill is a versatile tool, allowing different species to exploit tropical forest canopies, dry woodlands and even grasslands and semi-deserts. Its superficial resemblance to a cow's horn explains the group's name. The bill is straight in some species, but is more typically curved along its length. The alleged Eocene hornbill Geiseloceros robustus is not a hornbill at all, and undoubted hornbills are rare fossils in Miocene and post-Miocene strata. Yet their fossil record hardly reflects this. * Molecular clocks and fossil data from related bird groups show that hornbills had certainly appeared, and apparently undergone much of their initial diversification, during the Eocene. One Asian lineage then appears to have re-invaded Africa (Kemp 1995, Kinnaird & O'Brien 2007). Early in their evolution (apparently during the Eocene*), hornbills invaded Asia, and it is here that many kinds of tropical, forest-dwelling hornbill evolved (Viseshakul et al. What appear to be the most archaic of hornbills - the ground hornbills and the grassland-dwelling Tockus hornbills - are African. People have long revered these birds and, in some cultures, their images are incorporated into art, heraldry and architecture. Spectacular colours, gigantic bills and head crests, and remarkable pieces of behaviour make hornbills among the most obvious birds of the African and Asian tropics. Often flaunting bright colours and sometimes reaching huge sizes (the largest species have wingspans of 1.8 m), they're well known for their enormous, curved bills and large bony crests. Hornbills are among the most distinctive and spectacular of Old World tropical birds. For the back-story, see the previous owls article.