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. A dryland bird (ie a 'dry air' bird) - as long as it has access to water - can easily pant to cool itself. Hence they are forced to find alternative strategies. ![]() 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. These birds did dump heat from their bills, but not quite as efficiently as the toucans did, especially at lower temperatures. They studied Southern Yellow-billed Hornbills Tockus leucomelas, a fairly small hornbill of open country, including deserts, from southern Africa. ![]() 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. The answer is 'yes, but not quite so much'. 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 yellow is the hottest part, 10 degrees C above the temperature of the Low resolution shot from a video, showing a Toco Toucan dumping heat just before (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.) 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. 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'. At low temperatures the blood flow to the beak is closed off, and little or no heat is lost. 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. Using infra-red cameras they could see this happening, the heat being 'dumped' from its body to its bill, and thus to the atmosphere. 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. 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'. The casque on its bill is a feature of many hornbills. What can one say? This is a truly bizarre animal at first meeting,Īnd huge, far larger than the biggest toucan, being up to 90cm long and weighing It's also the biggest toucan, being over 60cm long and weighing nearly 700 grams.įemale Rhinoceros Hornbill Buceros rhinoceros, Kinabatangan River, Sabah, Seriously, but up close it's extraordinary - the Toco's beak, relative to body size, is the largest in I readily concede that it's almost too remarkable to take This is the archetypal toucan in many people's imaginations, unfortunately parodiedĪs a cartoon bird in many contexts. Toco Toucan Ramphastos toco, Iguazu Falls, Argentina. Let's meet an example of each to start with. Toucans are restricted to South and Central America, while hornbills are found throughout Africa and southern Asia from India to New Guinea. 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 share their Order with barbets and woodpeckers, hornbills with hoopoes and not much else. ![]() They belong not just to different Families but to different Orders, so are entirely unrelated. 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.) (I began my overseas birding adventures quite late in life, so I saw my first hornbill in 2003, and my first toucan in 2008. 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.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |