Longest Bill: Sword-Billed Hummingbird
There’s nothing subtle about the claim to fame of the sword-billed hummingbird (Ensifera ensifera), which ranges in Andean forests in South America. The remarkably extended bill is almost as long as the bird itself. The male averages 5-1/2 inches in length, with his bill stretching to 4 inches; the female is 5-1/8 inches long and her bill is a staggering 4-1/2 to 4-3/4 inches in length. No other bird in the world comes close to matching this species in terms of ratio of bill to overall length.

It is equally obvious why the sword-bill should be so endowed. Its bill is perfectly shaped to match the particular blooms from which it drinks. As plants and birds have coevolved, ever more extreme blooms have provided niches for ever more extreme bill shapes; the bird beats the competition, the plant assures its pollination. As for the sword-billed hummingbird, it specializes in plants with long, hanging blooms, such as daturas, passionflowers and fuchsias. These may not grow in the same profusion as other plants, but the nectar supply that each provides is rich and generous.

Of course, being so hyper-adapted causes some difficulties for this hummingbird. It must always perch and fly with its bill held up at a steep angle, otherwise it would become unbalanced. And preening can be a problem too: With the bill permanently out of action, the bird has to perform feather care with its feet.

Most Poisonous: Hooded Pitohui
In the summer of 1989 a biologist called Jack Dumbacher was studying birds of paradise in New Guinea. The project involved catching and banding the target birds and, at the same time, releasing the many other species caught in the mist nets alongside them. Among these were hooded pitohuis (Pitohui dichrous), common birds of the forest.

One day Dumbacher was attempting to release yet another collateral pitohui when the bird ungratefully pecked and scratched him. The field worker put his bleeding fingers in his mouth and immediately felt a curious numbing sensation. He recognized the feeling as being caused by a toxin, but it was not until he licked one of the bird’s feathers that he realized that these, and not some local plant, were the source of the poison. He had stumbled upon the very first recorded instance of toxicity in a bird’s plumage. Despite the fact that pitohuis had been known to science for hundreds of years, nobody had noticed the phenomenon before.

The toxin in the pitohui’s plumage is the same neurotoxin found on the skin of poisonous frogs in South America, though in lower levels. It is unlikely that a predator attacking a pitohui would be killed. Nevertheless, the effects would be sufficiently unpleasant at first bite to ensure that predators would give the bird a wide berth in the future. It is also possible that the toxins help to keep parasites off the pitohui’s skin and feathers.

Oddest Skin: Southern Screamer
This peculiar bird (Chauna torquata) is a member of a somewhat obscure family of South American birds known as the screamers. Despite their appearance, screamers are thought to be closely related to ducks and geese, although they have a few anatomical oddities that are very much their own. One of these is their skin.

If you were to reach out and touch a screamer (admittedly, not very likely), you would hear a distinct crackling sound. This is caused by a complicated system of small air sacs separating the outer skin from the rest of the body, which contracts to make the sound, like the bursting of hundreds of minute balloons. It is thought that these air sacs play a part in insulating the bird.

Another curious feature of screamers is that their bones are more highly pneumatized than those of any other bird—in other words, their internal structure is more hollowed out, making the bones exceptionally light. Oddly, the screamer’s rib cage also lacks the special strengthening known as the “uncinate process” that is present in all other bird bones. All in all, it seems, the sheer weirdness of screamers is more than skin deep.

Biggest Belly: Hoatzin
When resting, hoatzins (Opisthocomus hoazin) don’t normally perch but instead sit on their sternums. Their bellies can be so big and heavy that, when bending down from a low branch to take a sip of water, these South American birds have been known to topple over and splash calamitously in.

The large belly is the result of the hoatzin’s unusual and restrictive diet. It is one of the few birds to specialize in eating leaves, which can constitute up to 82 percent of its entire intake. Leaves are notoriously difficult to digest, and hoatzins, in common with many herbivores, rely on microbes to do the work for them. Microbes work best in a capacious gut where the flow of matter is not too fast, and where both the acidity and temperature remain constant. This partly explains the large size of the belly. However, in a break from all other birds, hoatzins provide the conditions in their foregut, instead of further back in the alimentary canal. Digestion takes place in the crop and esophagus, which is more akin to the system in sheep, cows and kangaroos.

Almost everything about this system seems awkward for the hoatzin. It cannot fly far, it cannot swim and it has great difficulty moving through the branches of the waterside plants where it lives. Still, leaves are never far away, and in the warm conditions of tropical waterways, this bird thrives as well as any of its more energetic neighbors.

Classiest Colors: Fischer’s Turaco
This African species’ feathers are suffused with some of the rarest pigments in the entire animal kingdom. Effectively the bird (Tuaraco fischeri) is a model, and it’s wearing designer plumages.

The two special pigments are called turacin and turacoverdin, named after the turaco family (Musophagidae)—a small group of 23 bird species found only in sub-Saharan Africa, of which the Fischer’s turaco is one. Both pigments are copper based, and so far, they have not been found in any other animals. Indeed, not all turacos have them.

Turacin is a red pigment that is mainly found on the wings, although on this Fischer’s turaco, it also adorns the crest and nap. Turacoverdin is a green pigment found throughout the body and its intensity is related to the habitat of the relevant species: Fisher’s turaco, for example, is a forest bird and has it in abundance. Even more interestingly, this is the only green pigment synthesized by any bird. All other green colors, from the wondrous iridescence of hummingbirds to the plainer green of warblers or finches, arise through structural modifications of the feathers that cause light to be refracted unequally.

Young turacos don’t acquire full adult colors until they are about a year old. It seems that the required amount of copper upon which the pigments depend takes that long to accumulate from the birds’ diet.

British writer Dominic Couzens specializes in birds and birding. This text is excerpted from his most recent book, Extreme Birds: The World’s Most Extraordinary and Bizarre Birds (Firefly Books, 2008; www.fireflybooks.com). The book is available for purchase at Amazon.

Text © 2008 by Dominic Couzens. All rights reserved. Published in North America by Firefly Books Ltd.