Saturday, 21 June 2014

Hornbills 3: Tarictic Hornbill

With an estimated world population of only 1800 birds, the Visayan Tarictic Hornbill Penolopides panini is probably one of the rarest hornbills in the world. Already one subspecies, P.panini ticaensis from the island of Ticao is extinct as a result of deforestation, despite being describes as “abundant” in 1905, which makes it the first known extinction in historic times of any hornbill taxon. Complicating the picture is that the species formerly included at least five other closely related species which have since been split. Unfortunately, before this was realised some had been crossed in the captive population, resulting in hybrids which were useless from a conservation point of view.

In the wild, as with other Asian hornbills, they inhabit primary rainforest. Being slightly smaller than the species I have covered previously on this blog (although still around the size of a crow) they can feed on smaller fruits than the large species, and probably have a different range of animal prey in the diet as well. Males and females are quite distinct, with the males having large areas of creamy white plumage. The natural range includes the islands of Masbate, Negros, and Panay in the Philippines. Other species of Penolopides inhabit Sulawesi, Luzon, and Mindanao and other islands. These same forests are home to some of the Bleeding Heart Doves that the zoo works with. We keep and breed the Luzon and Mindanao Bleeding Heart doves, and work with conservation organisations in the Philippines on the Negros Bleeding Heart as well in the home range countries. Sufficient Tarictic Hornbills have been bred in the Philippines for an experimental reintroduction project to be undertaken on Negros at the Philippines Biodiversity Conservation Foundation. For more information on the conservation of Philippines wildlife, see the website of the PBCF here:

Luzon Bleeding Heart Dove
As with the other hornbills we keep at the zoo, the pair we have are young. A month or so ago however I observed the male courtship feeding the female, which is a very good sign that we may breed them in the future. In the wild they travel around in small groups which probably engage in cooperative breeding as with many other species, especially in the tropics. In a cooperative breeding species other members of the flock, usually related to the breeding pair, assist in provisioning the young at the nest. However, for reasons of space it is usual to keep hornbills in pairs in captivity. They can be kept with other species, but smaller birds are at grave risk when the hornbills are breeding, as they will happily take them as prey when they have young to feed.
These predatory habits can also cause other problems. Any animal collection has a rodent problem – its unavoidable – but extreme caution is needed with rodent control as they will happily eat any rodent exposed to a rodenticide that wanders into their aviary, with potentially fatal results. This also exposes them to the disease pseudotuberculosis, caused by the microorganism Yersinia. This is also spread in the faeces of wild birds, and is a major cause of disease in animal collections. A vaccine exists, but needs to be repeated annually to maintain immunity.
One other husbandry issue is also found in other rainforest birds, and results from the different dietary composition in captivity. Iron storage disease (hemochromatosis) results from an excessive accumulation of iron in the system, resulting in liver damage and increased susceptibility to disease. A major factor is the lack of tannins and other compounds found in both the food and the water in a rainforest environment. These bind to iron in the bird’s digestive system and block absorption of iron. In captivity the water is usually lacking all these organic compounds and the fruit fed to them is lacking in iron chelators as well – in fact citrus fruits actually promote iron absorption. Now this has been realised appropriate steps can be taken to prevent the problem, including feeding pelleted diets formulated with a low iron content, and supplementing the water with tannins (of which the simplest method is supplying tea!)

Next week, I will conclude with the only African hornbill in the collection – the dry fortest loving Van der Decken’s Hornbill.
(Luzon Bleeding Heart Dove image from Bristol Zoo website)

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