Bird Buddy Blog

Evolution in birds – strange adaptations

Courtesy of PxHere

Over 9,000 species of birds exist, and all have evolved some sort of adaptation over millennia. Quadruple-insulated penguins to swivel-toed ospreys, birds exhibit some cunning ways to survive. Let’s take a look at a few … peculiar … examples.

Evolution is the process by which organisms go through physiological adaptations to try to better align with their environment, so that they can thrive and reproduce to the best of their abilities. It’s a common misconception that evolution is a progression towards something ultimate. The most often asked question about our own human development, when either innocently trying to understand or cynically trying to discredit the theory, is “why are there still monkeys / gorillas / chimpanzees if evolution exists?”

It’s a common misconception that evolution is a progression.

The problem with this angle (that all other primates should be progressing towards human form) is that it misunderstands the science behind evolution altogether: we aren’t the pinnacle of it, we are just another example of it. The clear answer to the above question is that we aren’t evolved from monkeys / gorillas / chimpanzees at all. They exist as their own species, we are all part of the Great Apes, and we have all evolved from a common ancestor. Gorillas and chimpanzees are doing just fine as they are, in evolutionary terms, and we are no “more” evolved than them.

Well oil be

Once this basic concept is understood, the appreciation of it is much enhanced. Some birds who exhibit incredible adaptations have simply had to do so to survive in their environments, and other birds in the same environment who have not developed such assets didn’t need to, won’t ever need to, and therefore never will.

Apart from the general adaptations across most bird species such as hollow bones for flight, different types of beak for the type of food consumed, and an incredibly efficient breathing system to ensure a constant flow of oxygen to cells, many of the unique differences in individual species are to do with diet.

Oilbirds are the world’s only flying fruit-eating nocturnal bird.

Take the oilbird, for example. The oilbird is mostly that – oil and bird. They were highly prized for their oil content from their food, and they used to be boiled down for fuel, but are now protected. They dine on the fruits of oil palm and tropical laurels, but they do so only at night. Oilbirds are the world’s only flying fruit-eating nocturnal bird, and they reside in caves deep in the forests of South America, although fossil records show they were once widely distributed around the globe. Their habitat is so specific that they have developed a number of adaptations to make the most of this world. Their eyes have the highest density of rod cells out of all the vertebrates, and their pupils dilate to the highest light-gathering capacity of all birds.

Courtesy of Wikimedia Commons

Roosting and breeding in caves, their feet have all but vanished, and their long wings have adapted to allow them to hover and twist through cave systems, and fly at very low speeds so that they don’t crash into hard rock faces. Despite being equipped with the best set of eyes a nocturnal animal could wish for, they also supplement their sight with echolocation, the only other species of bird in the world to do so, aside from some swifts. As they only nest in caves, which don’t tend to have a wealth of materials lying around, their nests are constructed from hardened droppings: the glossy white egg shells are quickly stained brown.

Wind beneath my wings

Another bird that is alleged to use something from its posterior is the Bassian thrush, widely distributed throughout Australia. Like most thrushes, this is a fairly standard-looking bird: streaked chest, brown back, midsize, eats worms, that sort of thing. However, for reasons best known to itself, the Bassian thrush has apparently adapted its cloaca as a tool for hunting. According to an observer in 1983, one was seen to emit regular bursts of audible flatulence toward worm casts. The tail would be seen to shiver five or six times and then dip, known as venting, and foliage beneath the tail was displaced outwards, as if by air. A sound resembling “a gasping inhalation” was said to have been heard, and this happened numerous times. After each vent, the thrush would immediately whip round and forage among the disturbed location. It was concluded that this unwelcome blast of rectal air provoked the worms into movement making them easier to detect.

Since the claim was made, regretfully there has been no conclusive research to confirm the theory. The Bassian thrush is very elusive and hard to spot, but if you are lucky enough to see one, it immediately runs off through the undergrowth if it senses you. Birds do have the anatomy to break wind, but it is assumed they rarely do. We’re not ruling this hunting technique out by any means, and we really hope it’s true.

Stomach turner

Sticking with the theme of unpleasant body odours, there is such a bird known as the hoatzin, tellingly also known as the stinkbird or skunkbird, which is found in the swamps and mangroves of rainforests. It is a folivore, meaning its diet consists of 80% leaves, with the rest made up of fruit and flowers and the odd unintentional insect. In itself this is perfectly normal, but the difference with this one is that its digestive system is unlike any other bird. To break down all that marshy matter, it ferments its food using bacteria, in exactly the same way that a ruminant does. It lacks the special stomach for this, however, and instead this beautiful process takes place in an unusually large crop below its beak. This makes the bird exceptionally fragrant, and not in a good way. As we mentioned earlier, evolution is a process but not a progression; there is huge debate amongst zoologists about where this bird evolved from and why, not helped by the fact that as a chick it has claws on its thumb-bone which disappear as the bird ages to adulthood. A genome sequence carried out in 2015 discovered that the hoatzin is the last surviving member of a family line that branched off on its own 64 million years ago.

Courtesy of Wikimedia Commons

It is an attractive bird, fairly large at around 26 inches / 65 cm tall, and very conspicuous with its russet wings, streaky white chest, maroon eyes set in a blue unfeathered face topped by a spiky crest, and it is quite noisy; it’s not hard to spot. But for some reason it has rarely ever been hunted. Maybe the evolution of the hoatzin to be the most fetid bird ever was the only way to secure its future.

This makes the bird exceptionally fragrant, and not in a good way.

Other less unsavoury bird adaptations exist, of course, such as the layers of different types of feathers on an emperor penguin, helping it insulate against Antarctic temperatures of -58°F / -50°C, or the fact that the osprey, also known as the fish eagle, is unique among raptors by having oil on its wings for protection against water and can swivel it’s outermost third front toe to the back of its foot when catching and carrying fish, so that it is as streamlined as possible.

Birds are already amazing creatures, and finding out more about their lives will always reveal something new and fascinating as the study of how they came to be, and what they may become, goes on.