Have you ever wished you were an eagle, soaring high above the prairie? How about the mythical phoenix, rising from the ashes? For centuries people have wistfully watched birds take wing and felt a bit jealous. But what about birds that don’t fly? You’d think they’d hold a grudge against their freewheeling cousins, but these guys are just as awesome in their own right. These eight birds can’t fly, but you should probably envy them anyway.
Continued presence of wings in flightless birds edit
With the exception of New Zealand moas, the wing structure has not been lost despite the lack of selection pressure for flight. [11] Emu runs have been recorded at 50 km/h, and ostriches are the world’s fastest runner birds. [8] The bird needs its wings to maintain balance at these high speeds and to act as a parachute to slow down. It is believed that wings were preserved because they were important for sexual selection in early ancestral ratites. These days, ostriches and rheas both exhibit this. These ratites make extensive use of their wings during displays to other males and during courtship. [12] Sexual selection affects the preservation of large body size as well, which deters flight. Ratites’ large size facilitates easier mate selection and increases the likelihood of successful reproduction. Because they are monogamous, rats and tinamous only mate a few times a year. High parental involvement indicates that selecting a trustworthy partner is essential. In an environment with a stable climate that offers year-round food supplies, a male’s claimed territory alerts females to the wealth of resources that are easily accessible to them and their progeny. [20] Male size also indicates his protective abilities. Like emperor penguins, male ratites spend 85–92 days incubating and guarding their young while the females feed. They can only survive on fat reserves and go up to a week without eating. There are records of emus fasting for up to 56 days. [8] Selection will lean toward these other features if there are no ongoing stresses that justify expending energy to maintain the flight structures.
Penguins’ wings are kept in their original structure so they can move underwater. [27] Penguins lost some of their aerial efficiency as a result of evolving their wing structure to become more efficient underwater. [28].
Hunted to extinction by humans by the 15th century, the massive, herbivorous moa of New Zealand was the only known species of flightless bird in which wings entirely vanished. The entire pectoral girdle in moa is reduced to a pair of finger-sized scapulocoracoids. [29].
History edit
Immediately following the K-Pg extinction event, which destroyed all non-avian dinosaurs and large vertebrates 66 million years ago, there were divergences and losses of flight within the ratite lineage. [6] Following the mass extinction, niches were quickly cleared out, giving Palaeognathes the chance to disperse and settle in new areas. By changing their morphology and behavior, new ecological influences selectively forced various taxa to converge on flightless modes of existence. The effective annexation and defense of a territory claimed by ratites, whose Tertiary ancestors were chosen for their large size and cursoriality [7] Throughout the Miocene, temperate rainforests dried out and turned into semiarid deserts, resulting in a wide dispersion of habitats over the increasingly diverse landmasses. Cursoriality was an economical way to cover large distances in order to obtain food, which was typically found in low-lying vegetation that was easier to walk to. [7] The distribution of ratite in semiarid grasslands and deserts today reflects remnants of these events. [8].
Bird gigantism and flightlessness are almost exclusively associated with islands that lack competition and mammalian or reptilian predators. Ratites, on the other hand, live in areas that are primarily inhabited by a variety of mammals. [10] It is believed that the breakup of the supercontinent Gondwana led to allopatric speciation, which is where they first originated. [11] Nevertheless, subsequent data indicates that Joel Cracraft’s 1974 theory is false. [12] Rather ratites lost their ability to fly multiple times within the lineage after arriving in their respective locations via a flighted ancestor.
Gigantism is not a requirement for flightlessness. Despite coexisting with the gigantism-exhibiting moa and rheas, the kiwi and tinamous do not display gigantism. This may be due to the arrival of distinct ancestral flighted birds or to competitive exclusion. [11] The large flightless herbivore or omnivore niche was occupied by the first flightless bird to arrive in each environment, forcing the subsequent arrivals to stay smaller. It’s possible that after the K/T Boundary, there were no voids in the environments for flightless birds to occupy. They were pushed out by other herbivorous mammals. [10].
More species of flightless birds than any other place were found in New Zealand, including the kiwi, several species of penguins, takahī, weka, moa, and several other extinct species. One explanation for this is that, prior to the advent of humans some a millennium ago, New Zealand was devoid of large land mammals; instead, larger birds served as the primary predators of flightless birds. [13].
Ratites are thought to have independently evolved flightlessness several times within their own group. They are members of the superorder Palaeognathae, which also includes the volant tinamou. [4][6][7][10] On oceanic islands, for example, some birds developed a lack of ability to fly in response to the lack of predators. Ratite phylogeny and Gondwana’s geological past are inconsistent, suggesting that flying birds caused a secondary invasion that led to ratites’ current distribution. [14] There’s still a chance that the tinamou regained flight after their most recent common ancestor, the ratites, was flightless. [15] Nonetheless, it is thought that losing flight is a simpler transition for birds than losing flight and then gaining it again, as this has never been recorded in the history of birds. Furthermore, the fact that tinamou nest inside flightless ratites suggests that ancestral ratites were volant and that several independent losses of flight occurred throughout the lineage. This suggests that convergent evolution is the cause of the ratites’ unique inability to fly. [16].
People have been jealous of birds for centuries. Have you ever wished you were an eagle, soaring high above the prairie? Or how about the mythical phoenix, rising from the ashes? What about birds that aren’t able to fly? You would think that they would be resentful of their more carefree relatives, but these birds are equally amazing on their own. Even though these eight birds are unable to fly, you should still be envious of them.
FAQ
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