Flightless Bird

Flightless birds are the birds that do not have the ability to fly like the common aves. They are generally referred to as non-flying birds. Although these birds lack the ability to fly, their anatomy and morphology indicate the presence of the wings, there might be some other anatomical benefits of the presence of such structure but they are used for aviation. The lost ability of aviation can be attributed to the adaptation mechanism for the new environment. According to evolutionary history, there are many taxonomical classification order that contains the series of flightless bird but in modern times almost all the living species are concentrated in the order called order Struthioniformes. This order has the highest species density of flightless birds in modern days. This article focuses on the origin of flightless birds, the evolution of flightless birds, and the adaptations and features of large flightless birds and the smallest flightless bird. 

What are Flightless Birds?

Flightless birds are sometimes more commonly referred to as non-flying birds. Some of the common flightless bird names include ostrich, penguin, dodo. As the name suggests these are the group of bird that has lost the ability of aviation during the course of evolution. Although they do not have the ability to fly, the typical wings or wing like structures are commonly seen in these birds. These structures suggest that maybe during some time in evolutionary flightless birds or their ancestors had the ability to flight but as a result of adaptation towards the new environment they lost it. It is important to note that although they lack the characteristic features of a bird many or we can say almost all of the flightless birds are still classified as Aves. the most number of flightless bird names is included in the order Struthioniformes. Common examples of flightless birds include penguins, dodo, ostrich, peacocks, emu, cassowaries, rheas, and kiwi.

What is the Reason for Flightless Adaptations of Birds?

It is clear from the discussion above that the birds that can not fly are still classified as aves, on a broad range the reason for the existence of such flightless animals can be attributed to evolution. But there are various reasons that lead to such adaptation that can result in the lost ability of aviation. Some of the reasons are mentioned below.

One of the common hypothesis suggests that the evolution of flightless birds were favored by natural selection because, in prehistoric times, the ancestor birds inhabited large areas supplied with resources. These habitats lacked the predator thus making the ability of flight unnecessary as it is a common defense used against predators by aves. Natural selection favored the development of large bodies and lost the ability to fly. The vestigial wings were still passed on to generations of progeny. Such birds completely or sometimes partially lost the ability to fly. Needless to say with a growing predator population such as rats, humans, and dogs, these birds were forced to develop other defense mechanisms one such adaptation of defense mechanism is the speed.

Another hypothesis of the adaption of flightless birds is selective breeding. This holds specifically true for birds that are bred in poultry. Example of such birds includes ducks, chickens, roosters. These birds are specifically bred to produce a high mass of breast meat, thus it increases the overall weight of the body. Selective breeding leads to a partial loss of ability for flight. The ancestor bird species of these birds like the red junglefowl and mallard, are capable of extended periods of flight but the modern domesticated bird species are not able to fly for an extended period of time. 

The third common hypothesis for the origin and selection of flightless birds was based on the principle of the K-Pg extinction event. According to this hypothesis, the  K-Pg extinction event almost wiped out three fourth of the population of flora and fauna on the planet, leaving the remaining taxa with low competition and large resources. Such conditions lead to the natural selection of gigantic birds and the ability of flight became relatively unnecessary thus favoring the natural selection of flightless birds, hence it can be concluded that the new ecological conditions influenced and selectively pressured different taxa to converge on flightless modes of existence by adapting them both morphologically and behaviorally.

Physical Characteristics

The physical characteristics of the bird include the lack of development of forelimbs. This is seen as an evolutionary adaptation of flightlessness. Evolutionary studies have also shown that these birds lack the same basic bone structure and muscles. One of the common examples is the absence of keel. In flying birds keel is the site of attachment to the muscles, it can be defined as the ridge on the sternum, or breastbone, which serves as the main point of attachment for flight muscles.

Another common physical characteristic seen in the flightless bird is the modification of the forelimb, the forelimb in some of the species of the bird are shaped like a paddle. This paddle structure ensures the high swimming abilities of the birds, these modifications are generally seen in the birds that are dependent on the aquatic ecosystem. An example of such a bird is the penguin.

Among the flightless birds, the phenomenon named as peramorphosis leads to enlargement of the pelvic girdle for running. Peramorphosis can be defined as the increased rate of development as a result of evolutionary changes. The development of the pelvic girdle is one such physical characteristic that leads to the development of high speed of running in flightless birds.

The Continued Presence of Wings

It is established in the understanding that wings are the organ that is necessary for birds to but the question that arises here is why are wings still present as a morphological feature of the completely flightless birds? Wings in flightless birds serve as an appendage that is used to maintain the balance of the body during locomotion (that is during running or walking). Another reason for the presence of the wings is the sexual selection of the trait. It is commonly seen in the peacocks although the tail of peacocks does not support flying they are still maintained because they provide a better chance at mating at the cost of survival fitness. Similarly, the wings of flightless birds also serve as the portrayal of dominance and health in the species, which may provide a better chance at mating. In certain species of flightless birds, their wings are extensively for courtship and display to other males. Examples of such flightless bird names include rheas and ostriches.

List of Flightless Birds

There are many large as well as small flightless birds. The largest flightless bird that is still surviving is the ostrich. The smallest flightless bird is Inaccessible Island Rail Atlantisia rogersi, this bird is found endemically in the Inaccessible Island, Tristan da Cunha archipelago, in the central South Atlantic Ocean. The flightless bird list including the common flightless bird names are mentioned below,

1. Ostriches

2. Emu

3. Kiwi

4. Moa

5. Elephant bird

6. Cassowaries

7. Rheas

8. Auckland Island teal,

9. Campbell teal, 

10. Steamer ducks

11. Fuegian steamer duck, 

12. New Caledonian giant scrubfowl

13. Noble megapode, 

14. Viti Levu scrubfowl,

15. Giant Hawaiian Goose

Extinct Species

There are various extinct species of flightless birds, there are several reasons that account for the extinction of the flightless birds. One of the main reasons is human activity. The extinct flightless bird includes the following

1. Elephant birds (Aepyornis, Mullerornis, and Vorombe) were found on the island of Madagascar.

2. dodo (Raphus cucullatus), the bird was found in Mauritius, they weighed about 23 kgs and are now considered extinct.

3. Moas, the large terrestrial flightless birds were believed to live in New Zealand, they are extinct due to human hunting. 

Conclusion

Flightless birds majorly belongs to the order Struthioniformes, they contain most of the species that are still surviving on the planet. The flightless birds are thought to be descended from the common aves, but due to evolutionary adaptations, and selective breeding the flightless birds developed. The common flightless bird names include kiwi, dodo, ostrich. The physical characteristic of these birds includes the absence of keel and short forelimbs. The common example of the extinct flightless birds includes moa and dodo.