Buzz
Birds are seen by most of us on a daily basis, and may appear to be familiar, typical creatures. While certain rare birds are especially perplexing, birds as a class are just weird. Strange physiological adaptations define many avian species, while aberrant partner selections and responses to predators epitomize oddness. We will explore the exceedingly weird traits of so-called ordinary birds and some logical but lesser-known facets of avian adaptation.
10. Birds Have Partially Inflatable Bones
Human bones are reasonably solid structures, except for some air spaces and the many hollow, marrow-containing sections. Bird bones, are not only hollow and strut-formed to reduce weight, but actually contain spaces for air sacs that play a role in boosting avian breathing capacity. A number of hollow bird bones actually contain some of the bird’s seven to nine air sacs linking to the lungs. The air sacs inflate, then feed into the lungs in a “negative pressure breathing system” that starkly contrasts with mammal respiration methods.
Birds lack diaphragms and must rely on muscular movements to inflate and deflate their air sacs. With this complex, indirect breathing system, birds must complete two breathing cycles to exchange air in the lungs once. Air sacs are extremely delicate and are found in an incredible array of places throughout the avian skeleton. Cervical air sacs, for example, extend into the vertebrae. Forward air sacs extend into the humerus bone of the wing, while rear air sacs enter the femur (thigh bone).
9. Birds Are On Their Toes
Because of a strange path of avian evolution, birds walk on their toes, and are therefore known as “digitigrades.” Their counter-intuitive leg and foot structures confuse the casual observer of feathered creatures. The leg, foot and toe arrangements of a bird are rather peculiar, thanks to the evolutionary adaptations of avian bipedalism that are functionally similar, but proportionally very different, to the human leg.
Birds have a typical thigh joint, but their true knee joint is hidden. The bend in a bird’s leg that we see in a standing avian may look like a backwards-facing, reversed knee. In fact, it is the bird’s ankle joint. What appears to be the lower leg below the “knee” is actually the bird’s extended foot bones, the tarsus and tarsometatarsus. The bird’s “foot” that we see is not the foot, but simply a collection of extended toe bones.
8. Woodpeckers Possess an Extraordinary Tongue and Skull Configuration
Thanks in part to amusing animated depictions such as Woody Woodpecker, the piciformes (woodpeckers) are firmly embedded in imagination and popular culture. Woodpeckers are known to have an incredibly powerful bill and a cushioned, thick skull that allows them to pound away at trees in search of prey. However, it is the nature of the tongue allowing woodpeckers to extract prey once a hole has been excavated that is especially bizarre. Woodpeckers, from the smallest piculets to the nearly mythical and possibly extinct ivory billed woodpecker, have the longest tongues in proportion to body size of all birds.
In a truly bizarre twist of adaption, a woodpecker’s tongue is actually anchored through hyoid horns at the front of the bird’s skull through the right nostril. It then routes around the skull, entering through the bill. Supported by the weird and long hyoid structure, the supremely thin tongue may be nearly as long as the woodpecker itself. The oral extender can flicker in and out to incredible lengths as insects are collected from every possible crevice.
7. Diving Ducks Exhibit Specialized Adaptations
In nature, every trait comes with its trade-offs. Dabbling ducks, like the common mallard, feed on the water's surface or forage at shallow pond edges. These birds are lightweight and do not dive. In contrast, diving ducks such as eiders, scoters, and goldeneyes inhabit open ocean waters, bays, and the deeper parts of lakes and ponds. To facilitate their dives to the bottom in search of food, diving ducks have evolved dense, heavy skeletal structures and a compact body shape.
This comes at the cost of their flying ability. As a result, diving ducks and similarly adapted waterbirds, such as cormorants or puffins, not only make a long run to take off, but are usually seen flying close to the surface of the water as they travel above the waves. By flying close to the water, a cushion of air from each down stroke helps these heavy birds to fly more efficiently than they would at a higher attitude. Dabbling ducks simply spring into the air and are often seen circling high overhead.
6. Avian Sibling Murder Is Widespread
Birds of a feather may flock together, but sibling rivalry takes a variety of deadly turns as natural selection starts at close quarters in the nest. In species such as raptors, sibling rivalry is so violent and intentional that it has become known to ornithologists as “Cainism” in reference to the biblical account of Cain’s murder of his brother, Abel. Birds of prey have more than one chick, but the larger, stronger, usually firstborn chick may use its powerful beak and talons to attack the weaker nestling, leading to its death in some cases. Parents do not intervene. Apparently, the surviving bird carries the strongest genes and is the chick most likely to return on parental investment with successful fledging and eventual reproduction.
Other common bird species, such as herons, may take a more passive approach to fratricide. The stronger bird competes for all the food, causing the weaker chick to starve. Some birds, such as kittiwakes, control their hormone levels and timing of hatching through varied sitting regimes to influence the success of particular chicks in times of limited resources.
5. Doves: An Exception In The Drinking Life Of Birds
Beaks are incredible adaptations, but they have limitations. The avian mouth is hardened and poorly adapted for sipping water against gravity. Birds generally scoop water with their bill, then quickly tip their heads to swallow. Only a small amount of water can be taken at a time, causing birds to repeatedly dip into their water source in the course of a single drink.
Doves, though not as "evolved" as other avian species like songbirds, possess a unique trait that grants them a significant advantage in water consumption. By inserting their slender, straw-like bills into water sources, doves and pigeons can rapidly draw up water, enabling them to hydrate in just 20 seconds. This efficient method reduces the time spent at water sources, thereby decreasing the risk of predation during these vulnerable moments.
4. The Myth of the Swan-Necked Bird
Birds are master illusionists. These disguised reptiles at heart have become the most beautiful creatures on Earth apart from tropical fish. Thought-provoking ornithologist and writer Gary Kaiser stated that "the inner bird is a goblin-like creature that controls its (nonliving) outer form of feathers through a system of short muscles linked to incredibly long ligaments, rather like a puppeteer." Now, we will introduce a bizarre fact that is no stretch—all birds are basically "swan-necked."
From the seemingly neckless budgie and penguin to the extravagant ostrich and flamingo, all birds possess a sinuous, S-shaped neck. Even birds with shorter necks have elongated vertebrae that allow them to fold their necks into an S shape, often concealed beneath feathers. This design provides flexibility and mobility, with the neck's length often hidden by plumage, as seen when a heron retracts its neck during flight.
3. The Mobbing Phenomenon
Certain bird species engage in a behavior known as mobbing, where groups of individuals or mixed-species assemblies collectively harass a predator, often another bird. This behavior continues to puzzle scientists, who observe species such as songbirds, hummingbirds, and terns repeatedly swooping towards, pecking, or sitting beside a predator spotted in the area.
Scientists debate the exact purpose of mobbing, but suspect that multiple factors may be at play. Birds may mob to get predators to move along, to raise awareness of a predator’s presence, or to eliminate the element of surprise in a successful attack. The fact that mobbed predators do not turn around and kill their tormenters suggests that the element of surprise is vital for a successful hunt.
Research indicates that mobbing may be intended to prevent risks to breeding territory, especially young birds. In a 2005 study of warbler behavior, mobbing was inextricably tied to breeding location. Spectacular mobbing examples observed during field studies include aerial combat between blackbirds and raptors and the surrounding of a small owl by highly aggravated thrushes, towhees, several chickadees, and a nuthatch.
2. Avian Hybridization: Common and Extraordinary
While many bird species are unique, the blending of species boundaries leads to surprisingly frequent cases of avian hybridization. It's estimated that up to 10% of the approximately 10,000 bird species worldwide have successfully hybridized in the wild. These hybrids can be highly confusing and especially bizarre, and such occurrences are even more common when multiple captive bird species are kept in close proximity.
Bird hybridization can span even greater taxonomic distances, resulting in hybrids between birds of different genera. Examples include the spectacular galahtiel (a cross between a galah cockatoo and the familiar cockatiel) or the crossing of completely distinct raptor species, herons, or songbirds. Duck hybridization can take a profound turn, with hybrids known to have occurred between the rather typical common goldeneye and the rakish, tooth-bearing hooded merganser.
1. All Birds Have Enormous Hidden Eyeballs
Birds possess exceptional vision, with their eyes occupying a significant portion of their skulls. Raptors, for instance, can detect prey from distances up to 8 kilometers (5 miles) and navigate through forests at speeds exceeding 18 meters per second (40 mph). Songbirds, on the other hand, can easily spot the smallest insects.
To achieve such remarkable visual acuity and processing speed, birds have large eyes. The majority of a bird's eyeball is concealed within its orbital socket, giving the face a typical appearance. However, the eyes of a typical bird, such as the familiar robin or finch, occupy a substantial portion of the skull, up to 15% of its head mass. In contrast, human eyes account for only 1% of head mass.
