Big Bills - That's Cool! Toucans and Hornbills

Believe it or not, there is a point to that title! Both these families of birds have entranced me since I first encountered them on opposite sides of the world. (I began my overseas birding adventures quite late in life, so I saw my first hornbill in 2003, and my first toucan in 2008. Since then, I've just discovered, I've coincidentally seen 24 of each - not enough of course, and I wonder if there'll ever be an opportunity to see more, or even just enjoy the same ones again.)

They belong not just to different Families but to different Orders, so are entirely unrelated. Toucans share their Order with barbets and woodpeckers, hornbills with hoopoes and not much else. What they have in common is their conspicuous great bills, sometimes to the point of being outrageous (though only to our eyes of course!). Toucans are restricted to South and Central America, while hornbills are found throughout Africa and southern Asia from India to New Guinea. Let's meet an example of each to start with.

Toco Toucan Ramphastos toco, Iguazu Falls, Argentina.
This is the archetypal toucan in many people's imaginations, unfortunately parodied
as a cartoon bird in many contexts. I readily concede that it's almost too remarkable to take
seriously, but up close it's extraordinary - the Toco's beak, relative to body size, is the largest in
the entire bird world. It's also the biggest toucan, being over 60cm long and weighing nearly 700 grams.

Female Rhinoceros Hornbill Buceros rhinoceros, Kinabatangan River, Sabah,
Malaysian Borneo. What can one say? This is a truly bizarre animal at first meeting,
and huge, far larger than the biggest toucan, being up to 90cm long and weighing
nearly three kilograms. The casque on its bill is a feature of many hornbills.

Despite being massive in the largest toucans, their beak is also remarkably light. It's a fascinating structure, comprising a network of thin bony struts, containing light spongy keratin (the protein that forms hair, skin and nails).

 

The obvious question of course though is 'why?', with regard to these extravagant beaks. I'm going to discuss the two groups separately for simplicity, staring with toucans. These are mostly fruit-eaters, though they'll readily take small animals, especially lizards and frogs, as they encounter them. (Many lodges attract toucans with fruit tables, as you'll see in some of the following photos.) They are also notorious nest-robbers, taking both chicks and eggs from hanging nests and tree hollows. Other birds will often attack any toucan that comes near their nest. The large bill does not seem to offer any advantages in picking and swallowing fruit - in fact a toucan has to take any food item in its bill tip and toss it back whole to swallow, so the opposite would seem to be true. On the other hand a long bill gives an obvious advantage in reaching into deep nests, especially in hollows.

Many toucans (like the Toco above) have beaks that are brightly coloured or patterned, and presumably play a role in courtship, though that was surely not the original driving force - and many others have plain-coloured beaks.

Lettered Aracaris Pteroglossus inscriptus, Chapada dos Guimarães, western Brazil.
You may want to click on the photo to see the bills better.

'Aracari' is the name used for the mostly brightly coloured members of this genus; it derives, via Portuguese, from a word from the Tupi language of coastal Brazil, now sadly lost. My guess is that the word referred to a particular species, but it's only a guess.  'Toucan' itself has the same origin, from a word like tukana. (This language also brought us words like 'jacana' and 'jabiru'.)

In 2009 a team of scientists from Canada and Brazil published a paper showing that the Toco Toucan's bill has a vital role as a 'controllable vascular thermal radiator'. In plainer words, the bill has a complex network of blood vessels which can be dilated or constricted at will to promote or control heat loss through the bill. Using infra-red cameras they could see this happening, the heat being 'dumped' from its body to its bill, and thus to the atmosphere. This is a key need for birds which live in the tropics, especially large ones and, like most toucans, spend a lot of time in the exposed canopy. At  low temperatures the blood flow to the beak is closed off, and little or no heat is lost. They conclude that the Toco's bill is 'one of the largest thermal windows in the animal kingdom, rivaling elephants’ ears in its ability to radiate body heat'. So obviously the feeding and display functions are very important in shaping the toucan's bill, but this role of a 'heat dump' is also crucial. (I should say too that in the course of researching this post, I discovered that this idea had been proposed as long ago as 1985.)

Low resolution shot from a video, showing a Toco Toucan dumping heat just before
going to sleep. The yellow is the hottest part, 10 degrees C above the temperature of the
feathers. Courtesy of Wired.

In my next post I'm going to explore ways in which some other animals deal with the need to regulate body temperature, but for now let's get back to the toucans, and meet some more.

Toucans nest in hollows, but their bills aren't robust enough for serious excavation, so they generally use hollows prepared by someone else, often a woodpecker.

Plate-billed Mountain Toucan Andigena laminirostris, Bellavista Lodge north of Quito, Ecuador.
This bird wasn't keen to let me get any closer while it was on its nest hollow.

A less-noticed feature of toucans is their feet, which are zygodactyl, that is the two middle toes grip forwards and the outer two go backwards - you might want to save this for a scrabble opportunity. Or something.

Green-billed Toucan Ramphastos dicolorus, Atlantic forests near Sao Paulo, Brazil.
You can see the foot structure quite well here, I think. You can also see another
toucan characteristic, which is the bare patch of skin around the eye. This patch
sometimes matches the adjacent bill, but not here.

All toucans are forest birds, except for the Toco, which is also found in savannahs and open woodland.

Chestnut-mandibled Toucan Ramphastos ambiguus swainsonii, Milpe Reserve,
Ecuadorian Andes, north of Quito Brazil. This is sometimes recognised
as a full species, but more usually seen as a sub-species of Yellow-throated Toucan.

There are five genera of toucans, all of which I can fortunately introduce you to, meeting more of the family by way of wrapping up this part of the post.

The green toucanets, genus Aulacorhynchus, comprising 11 species of (as you'd expect) small, mostly green, toucans of the mountain forests. Unfortunately I can only offer one here, as I've found them fairly shy and in the canopy - not this one though!

Crimson-rumped Toucanet Aulacorhynchus haematopygus, Mirador Rio Blanco, north of Quito,
Ecuador. This is a little restaurant on the way to the famed birders' mecca of the Mindo
Valley, where birds come to fruit feeders on the other side of a big window.

There are 14 aracaris, genus Pteroglossus. We met the Lettered Aracaris above; here are a few more. They tend to be brightly coloured and large-billed; as you'll see they're not at all averse to visiting feeders either.

Pale-mandibled Aracari Pteroglossus erythropygius, another visitor to the Mirador Rio Blanco
feeders. The characteristic 'teeth' of a toucan bill are obvious here.

Many-banded Aracari Pteroglossus pluricinctus, Wild Sumaco Lodge, on the eastern
slopes of the Andes in northern Ecuador.

Chestnut-eared Aracari Pteroglossus castanotis, Iguaçu Falls Brazil.
(This is the Portuguese spelling of the falls, as used in Brazil. The spelling used
above in the Toco Toucan caption is Spanish, as of course used in Argentina.)
This is a widespread and familiar toucan east of the Andes.

Collared Aracari Pteroglossus torquatus, central Costa Rica. It is found in lowland
forests from southern Mexico to Ecuador.

And lastly, an 'honorary aracari', the gorgeous and unexpected Saffron Toucanet Pteroglossus bailloni. It is so distinctive that it used to be placed in its own genus, but recent DNA work has told a different tale.

Saffron Toucanet, Trilha dos Toucanos Lodge, inland from Sao Paulo, Brazil.
This is one of many species reliant on the perilously reduced Atlantic Forests
of near-coastal Brazil.

There are six of the awkwardly named 'dichromatic toucanets', in genus Selenidera. It simply means that males and females are differently coloured. Here's an example.

Golden-collared Toucanets Selenidera reinwardtii feeding on cecropia fruit,
Wild Sumaco Lodge, eastern Andes, Ecuador.
Female above, male below.

The four mountain toucans of genus Andigena live in the high misty cloud forests of the Andes. I find them especially handsome.

Grey-breasted Mountain Toucan Andigena hypoglauca, El Cajas NP, southern Ecuador.

Finally the big 'typical toucans', genus Ramphastos, a few of which we've already met.

Channel-billed Toucan Ramphastos vitellinus, Chapada dos Guimarães, western Brazil.
This one was being very coy, but I can't leave out that lovely blue face!

Yellow-throated Toucan Ramphastos ambiguus attracted by the same cecropia fruits
at Wild Sumaca as the Golden-collared Toucanets above.

You'll probably be relieved at the news that I'm not going to go into as much detail about the hornbills, but they're too interesting and impressive to ignore, and surely you'll want to hear the answer to the question 'but what about their bills? Heat radiators too?'. The answer is 'yes, but not quite so much'. This work was done more recently, in 2016, by a group of South African researchers who were inspired by the work on toucan bills to see if the same principle applied to hornbills. They studied Southern Yellow-billed Hornbills Tockus leucomelas, a fairly small hornbill of open country, including deserts, from southern Africa. These birds did dump heat from their bills, but not quite as efficiently as the toucans did, especially at lower temperatures. This may be to do with the difficulty of losing heat by panting, which involves evaporative cooling from the inside of the mouth, in humid conditions such as the toucans experience. Hence they are forced to find alternative strategies. A dryland bird (ie a 'dry air' bird) - as long as it has access to water - can easily pant to cool itself. There is also the fact that a hornbill's bill is much heavier than that of a toucan of the same size, and the more solid structure may be less efficient at managing blood vessels than the toucan's spongy one. However the real point is that a hornbill's bill is still a very useful way of dumping excess body heat.

Eastern Yellow-billed Hornbill Tockus flavirostris, Shaba Reserve, northern Kenya.
This is a desert hornbill very similar to, and closely related to, the Southern Yellow-billeds
that the study was carried out on; indeed they were until recently regarded as the same species.
(Needless to say, I don't have a photo of them!)

More recent work (published in 2020 by another South African team) on the biggest hornbill of all reinforced this finding, though in this case the large areas of bare skin on the face and throat were also significant.
 

The Southern Ground Hornbill Bucorvus leadbeateri, Tarangire NP, Tanzania.
This is an enormous bird, up to a metre high and weighing up to 6kg. They prowl
through the grasslands in gangs, eating any animal they encounter, including hares,
squirrels and tortoises, though most of their food is invertebrates.
The two species of ground hornbills are now put in their own family, but
they are closely related to the true hornbills.

Uniquely, as you may well be aware from various wildlife documentaries, female hornbills seal themselves into a nesting hollow with mud, leaving only a narrow opening to allow the male to feed her, and later the chicks. When the chicks get too big she breaks out, but reseals them inside for safety until it's time for them to fledge.

I mentioned the casques on some species, which apparently act as resonating chambers. These are bony structures, adding further to the weight of the bill. As a result, hornbills not only have very strong neck muscles, but the top two vertebrae are fused for added strength.

Black-and-White Casqued Hornbill Bycanistes subcylindricus,
Entebbe Botanic Gardens, Uganda, one of a genus of mostly large African forest hornbills.
This is a male - the female's casque is smaller.

Silvery-cheeked Hornbill Bycanistes brevis, Mount Kenya, this time a female.
This one is in the  same genus as the previous bird.

Male Wrinkled Hornbill Rhabdotorrhinus corrugatus, Kinabatangan River, Sabah.
One of a group of four hornbills from Malaysia, Indonesia and the Philippines.
An Endangered species which requires large areas of undisturbed lowland rainforest.

Rhinoceros Hornbill again, Sepilok, Sabah, because just one really isn't enough!
This is the State Bird of Sarawak, also in Malaysian Borneo, but also the national bird
of Malaysia itself. Compare the black-rimmed red eyes of this male with the red-rimmed
white eyes of the female near the start of the post.

Oriental Pied Hornbill Anthracoceros albirostris, a big hornbill found widely
in south and south-east Asia.

Some species have casques that are very modest, and probably do no more than provide some structural support for the bill.

Bushy-crowned Hornbills Anorrhinus galeritus, Sepilok, Sabah.

Crowned Hornbill Lophoceros alboterminatus, Arusha, Tanzania.

 One final observation on hornbills - along with ostriches they are the only birds (as far as I know) to have 'eyebrows', which are really single filament rictal feathers. Presumably they perform the same protective role that ours do, though I wonder why more birds don't have them?

Oriental Pied Horbill, Labuk Bay, Sabah, Malaysian Borneo.
Click on the photo to see the 'eyelashes' clearly.

And I think it's time to wind this post up - thank you if you've read this far! - with three last non-casqued hornbills from African woodlands, all in the same genus.

Northern Red-billed Hornbill Tockus erythrorhynchus Shaba Reserve, northern Kenya.

Tanzanian Red-billed Hornbill Tockus ruahae, Serengeti NP, Tanzania.
What was previously 'the Red-billed Hornbill' has recently been divided into four species.

Von der Dekken's Hornbill Tockus deckeni, Serengeti NP.

And that is the end of this big-billed odyssey! If you've followed this right through, I'm grateful though of course I'll never know. I hope you've found something here that is interesting, or just enjoyable. We've covered a lot birds, countries and ideas, and that's never a bad thing, perhaps especially in these unsettling times.

 

As mentioned I'm going to return next time to the concept of how some animals deal with the problem of over-heating; I hope you'll join me.

NEXT POSTING THURSDAY 7 October
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