Wednesday, September 21, 2011

Advice from little hornbills

Crowned Hornbill, Tockus alboterminatus, in trees near the shore 
of Lake Victoria, at Mabamba Swamp, Uganda

My first exposure to hornbills was likely Disney’s Lion King, where Zazu tries to keep Simba out of trouble. Much to my dismay, Zazu appears to be a fictionalized hornbill species. I can’t find a match*. The only “little hornbills” are the dwarf-hornbills of the Congo rainforest and Western Africa, and even they are not that small. Certainly, none of the hornbills have given me any advice, although I am no king lion.

Red-billed Hornbill, Tockus erythrorhynchus, West of Arusha, 
near Tarangire National Park, Tanzania. This is the species the Lion King
character Zazu is based, but see my discussion at the bottom of the page.

Hornbills are pretty special birds. They have long tails and are relatively large compared to most birds, ranging from 38 to 100 centimeters in length (about 15 to 40 inches). Hornbills have thick, down curved bills; some hornbills have large keratin casques that extend from the head over the bill. Hornbills are loud in their calls, hooting, rasping, and piping various sounds. Especially with the bigger species, they are noisy in flight too. In the West Usambara forests of Tanzania, I took pause to describe in my notes the sound of the Silvery-cheeked Hornbill in flight, a “huuh-huuh-huuh,” each “huuh” being a downward thrust of its wings. 

Von der Decken’s Hornbill, Tockus deckeni, West of Arusha, 
near Tarangire National Park, Tanzania

Hornbills are omnivores. They eat fruits, invertebrates, and small vertebrates like lizards. You will sometimes see a hornbill flick up its bill, tossing the food into the air, and catch its food further back in its mouth. 

African Pied Hornbill, Tockus fasciatus, Mabira Forest, Uganda

There are about 56 hornbill species in the world and that number may increase if certain subspecies are considered distinct. Different hornbill species live in different habitats, from savannas to rain forests. Twenty-four species (of the 56) can be found in Africa. The rest are in tropical Asia. We have a couple of birding friends who have lived in Asia and tell us that African hornbills have nothing on Asian hornbills. If that is the case, I have no idea, because all my hornbill sightings have been in Africa. 

African Grey Hornbill, Tockus nasutus, Akagera National Park, Rwanda

Michele and I have seen twelve species of hornbills, including the ground-hornbills. In some places, hornbills are quite common. In central-eastern Uganda, where native trees and even small patches of forest remain, hornbills could often be heard and fairly easily seen, especially the large Black-and-white-casqued Hornbill. In Rwanda, in my experience, I have only seen one hornbill out of a national park once, and that was by one of the only tiny native-wooded areas left. The Black-and-white-casqued Hornbill was present in Nyungwe Forest in Rwanda, but it was never easily seen (in fact a group of birders that we met there missed them altogether). I suspect that Rwanda’s lack of abundant hornbills outside protected areas has to do with the fact that nearly all its large native trees outside the parks are gone (hornbills breed in large trees). 

Black-and-white-casqued Hornbill, Bycanistes subcylindricus,
Entebbe Botanical Gardens, Uganda.  Note that the male on the left has
a larger casque and the female on the right has red bare skin around her eye.
This is a good example of sexual dimorphism, which means that males
and females of the same species differ in shape, plumage, or size.

With the sunbirds or weavers, the males are bright, and admittedly I photograph the males more than the females. But upon reviewing my shots of the hornbills, they were also all male. Female hornbills are very similar if not identical in plumage and their bills only differ in size of the casque and sometimes color. Why were there all males in the pictures? Michele suggested that maybe the males are showier; in fact, she was very close!

White-thighed Hornbill, Bycanistes cylindricus, Budongo Forest, Uganda.
The male and  female display very similar sex differences as the above
black-and-white-casqued hornbills. These two species are very similar
but can be told apart by amount of white on their primary feathers and the
differences in their tail feathers.

Hornbills have a unique reproductive strategy that makes the females less visible during parts of the year. The female hornbill seals herself in a tree cavity with the eggs, where she incubates them and rears the young. The male brings food to feed her and the young until the young birds are nearly ready to fly out. She even molts, losing her flying feathers, during her time inside the tree. All species of hornbills breed like this except the ground-hornbills.

Silvery-cheeked Hornbill (female), Bycanistes brevis, Amani Rainforest,
East Usambara Mountains, Tanzania

Silvery-cheeked Hornbill (male), Bycanistes brevis,
Lake Manyara National Park, Tanzania

The ground-hornbills are unique (endemic) to Africa. Ground-hornbills are also different from all other hornbills in several ways. The two species of ground-hornbills have different ranges, with one basically in Africa north of equator and the other in Africa south of the equator. Visually, they differ in two main ways. First, the casque on the bill of the Abyssianian species is larger and more pronounced than the Southern species. Second, the coloration of the exposed skin on the neck and face of each species is different. The Abyssinian has blue skin around the eye and on the neck with the male having a red neck with a blue patch. The Southern has red skin around the eye and on the neck with the female having a red neck with a dark blue patch. It sounds confusing, but these are huge birds without much overlap in range, so they are easy IDs.

Southern Ground-hornbill, Bucorvus leadbeateri, Lake Manyara
National Park, Tanzania. While this photo is poor, is hows the bird
in the process of flipping up food to catch further back in its mouth.

Abyssinian Ground-hornbill (male), Bucorvus abyssinicus,
Murchison Falls National Park, Uganda

Abyssinian Ground-hornbill (male), Bucorvus abyssinicus,
Murchison Falls National Park, Uganda. They fly too!

Abyssinian Ground-hornbill (female left, male right), Bucorvus abyssinicus,
Murchison Falls National Park, Uganda

The two hornbills that we saw but did not photograph are the Piping Hornbills and the Trumpeter Hornbills. If there is any advice to be taken from hornbills, it is that you need to take a lot of photos to get a good shot. And to keep big native trees so that birds can nest in them!!

* According to the Lion King Wiki, Zazu is a red-billed hornbill. This species would make sense in terms of distribution and habitat. The bill is red and it does have some yellow at the base. However, there are some serious differences between Zazu and red-billed hornbills. Differences are extremely important in birding, and the following differences are more than enough to say Zazu is not a red-billed hornbill.

Zazu’s tail has a white line going across the center of his tail feathers; red-billed hornbills have white trailing down the edges of their outer tail feathers with no white line going across. Legs and feet of Zazu are red, whereas red-billed hornbill legs and feet are black. Zazu has one white bar on his wings whereas red-billed hornbills have white splotches all over their wings. Zazu has no yellow bare skin around the eyes whereas red-billed hornbills do. Zazu is blue, light blue, and white. Red-billed hornbills are black and white.

These differences are major enough to rule him out as a red-billed hornbill (the argument of simplification in kids’ movies is possibly valid until you see that other illustrated birds in animated movies have the details near-exact). I am not trying to split hairs here with Zazu’s illustrators or imply that an animated bird should be true to form. I think it is cool to see species that are famous from movies or are exhibited in zoos; in this case, there is no Zazu species to see.

Works Consulted

  • Fanshawe, J. and Stevenson, T. Birds of East Africa. Princeton and Oxford: Princeton University Press, 2002.
  • Pearson, D.J., Turner, A.T. and Zimmerman, D.A. Birds of Kenya & Northern Tanzania. Christopher Helm: London, 1999.
  • Roberson, Don. "HORNBILLS: Bucerotidae." Bird Families of the World. Accessed 21 September 2011.
  • Roberson, Don. "GROUND-HORNBILLS: Bucorvidae." Bird Families of the World. Accessed 21 September 2011.
  • Ryan, P. and Sinclair, I. Birds of Africa south of the Sahara. Struik Nature: Cape Town, 2003

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