Flightless bird

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Flightless birds evolved from flightless precursors. There are about 40 recent flightless bird species.

Conditions of flight ability

ostrich

While many genes have to be carefully coordinated to develop a skill as complex as flight , the lack of a gene can lead to inability to fly.

The bird must not be too heavy for this. Because due to physics, the required wing area increases disproportionately with increasing weight, F ~ G ^ 3/2. And these wings must also be moved by appropriately strong muscles, which makes the bird heavier again. As mentioned below (swan, great bustard, condor), this limit is a good 15 kg. Significantly heavier birds can no longer be able to fly. This is why small birds and insects can easily fly up from a standing position, while increasingly heavier birds need more and more run-up or can only fly off from elevated locations. In order for a bird to fly, it also needs sufficient coordination of movements in the brain and sensory organs that are powerful enough to control the flight appropriately. If just one of these elements is lost, the bird will be unable to fly.

Therefore it is much easier for an animal capable of flying to lose its ability to fly than for an animal that is unable to fly to acquire the ability to fly.

In the past, some researchers assumed that the ratites , which comprise most of the Great Pine Birds , descended from exclusively flightless ancestors. According to the current state of knowledge, however, they also descend from ancestors capable of flying.

Inability to fly usually arises from the fact that the development of the wings stops at a level typical of young animals or even animals that are still in the egg. This is often associated with the retention of youthful characteristics ( neoteny ) in other areas such as plumage coloration.

Flightless birds on the mainland

There are few flightless birds on the mainland, such as the ostrich , cassowary , emus and rhea . This is because the ability to fly there offers considerable advantages in escaping from predators and therefore only birds that are too big to fly lose their ability to fly. The largest recent flightable bird species (e.g. some swans , pelicans , bustards or the Andean condor ) weigh around 15–19 kg.

Birds that have given up the ability to fly in favor of better swimming or diving

Penguin in the water

In the sea there are flightless penguins and, earlier, the giant alk, as well as three types of steamboat ducks (tachyeres), which use their wings as fins and can therefore no longer fly. The long-winged steamship duck and various other alkenbirds also use their wings as fins, but have not receded them so far that they can no longer fly.

Grebes do not use their wings as fins, but they are relatively heavy for their size because their bones do not contain air chambers. This helps them dive for food, but makes it harder for them to get out of the water. Three species are flightless: the titicaca diver , the atitlánt diver (extinct) and the puna diver .

Fossil flightless diving birds are the Hesperornithiformes .

Island birds

Kakapo ( Strigops habroptilus )

The large ground-dwelling predators (real predators) are absent on islands , as the island usually does not offer them enough space for a permanent population and they could not immigrate over water over such great distances.

Flying does not offer as good protection against flying birds of prey as immersion in water or hiding in the bushes. Therefore, even very small birds have few natural enemies and a population of birds on such an island is usually so large that only a few young animals grow up because they starve to death beforehand due to the food competition between the birds. One advantage of the inability to fly is that the birds can save the energy to build up their flight muscles and to fly themselves and are therefore more likely to survive if there is a lack of food.

Island birds are more likely to invest their energy in a few large eggs than in many small eggs for the same reason. This gives the young birds from birth a certain lead over the young from larger clutches with smaller eggs. If the parent animals have fewer young to look after, they can offer more food to each of the animals so that they do not starve and grow faster. Since there are few predators, high reproduction rates are not necessary for a sufficient proportion of the young to survive to replace the old animals that are caught annually by predators or that have died of old age and accidents.

The ancestors of the flightless birds flew to the islands. But once a species is unable to fly, it cannot migrate to another island that is far away. Nevertheless, there are in principle the same ecological niches to occupy on every island and very similar flightless bird species arise again and again through parallel evolution. Because of this similarity, it has long been believed that these island birds are more closely related to each other than to their flight relatives, whose bone structure is extremely different. In fact, the closest relative of a flightless species is usually able to fly. Exceptions occur almost only for species that live on neighboring islands that were connected to one another in the last Ice Age, as the sea level was 100–150 m lower then than it is today.

Before the first humans set foot on the islands, every Polynesian island had at least two species of flightless birds. After their home islands were colonized by Polynesians or Europeans, many of them became extinct . Reasons for this are hunting , introduced predators ( dogs , rats , cats ) and habitat destruction. The flightless species are particularly susceptible to hunting and predators because of their inability to fly, their often great tameness and their low reproduction rates.

List of birds that have lost their ability to fly on islands free from land predators

An adult takahe feeds its cub

Great jawbirds :

Elephant birds (Aepyornithidae), moas (Dinornithiformes), kiwis (Apterygidae)

New jaw birds :

Flightless domestic birds

There are some breeds of domestic birds that are flightless. A common reason for this is silk flossiness, which also occurs in wild flightless birds such as the kiwi and does not otherwise harm the animals' well-being. An example of a silky feathered domestic bird is the silkie . Further examples of the flightlessness of domestic birds are the feather duster among the budgerigars and the "floor rollers" among the domestic pigeons, the ragged feathers in the domestic fowl and the combination of feather bonnet and feather rosette in the Japanese seagull . Some of the causative mutations are considered torture breeding .

literature

  • Michael D. Sorenson, Alan Cooper, Ellen Paxinos, Thomas W. Quinn, Helen F. James, Storrs L. Olson, Robert C. Fleischer : Relationships of the extinct moa-nalos, flightless Hawaiian waterfowl, based on ancient DNA. In: Proceedings of the Royal Society of London. Series B, Biological sciences. 1999, ISSN  0080-4649 , pp. 2187-2193.

Web links

  • Kersti Nebelsiek: Flightless birds. In: kersti.de. November 2008 .;

swell

  1. ^ Steven A. Trewick: Sympatric flightless rails Gallirallus dieffenbachii and G. modestus on the Chatham Islands, New Zealand; morphometrics and alternative evolutionary scenarios. In: Journal of The Royal Society of New Zealand. Volume 27, Number 4, December 1997, pp. 451-464.
  2. ↑ Storrs L. Olson: A classification of the rallidae. In: The Wilson Bulletin. Vol. 85, no. December 4, 1973.
  3. ^ A b Bradley C. Livezey: Evolutionary Morphology of Flightlessness in the Auckland Islands Teal. In: The Condor. Vol. 92, no. 3, Aug 1990, pp. 639-673. doi: 10.2307 / 1368685
  4. ^ BC Livezey: The carpometacarpus of Apterornis. In: Notornis. 41 (1), 1994, pp. 51-60.
  5. ^ Brian K. McNab: Energy Conservation and the Evolution of Flightlessness in Birds. In: The American Naturalist. Vol. 144, No. 4, October 1994, pp. 628-642.
  6. ↑ Derek A. Roff: The evolution of flightlessness: Is history important? In: Evolutionary Ecology. Volume 8, Number 6, November 1994, pp. 639-657, doi: 10.1007 / BF01237847 .
  7. ^ Irenäus Eibl-Eibesfeldt: Galápagos. Noah's Ark in the Pacific. Piper, Munich / Zurich 1991.
  8. ↑ J. Bried, D. Pontier, P. Jouventin: Mate fidelity in monogamous birds: a re-examination of the Procellariiformes. In: Animal Behavior. Vol. 65, no. 1, January 2003, pp. 235-246.
  9. ^ Carlos A. Valle: Effective Population Size and Demography of the Rare Flightless Galapagos Cormorant. In: Ecological Applications. Vol. 5, No. 3, Aug 1995, pp. 601-617, doi: 10.2307 / 1941970 .
  10. ^ R. Tindle: The evolution of breeding strategies in the flightless cormorant (Nannopterum harrisi) of the Galapagos. In: Biological Journal of the Linnean Society. 1984.
  11. ^ Walter Rothschild: The Avifauna of Laysan and the neighboring islands with a complete history to date of the birds of the Hawaiian possession. RH Porter, London 1893-1900. (on-line)
  12. ^ J. Mark Jenkins: Natural History of the Guam Rail. In: The Condor. Vol. 81, No. 4, Nov 1979, pp. 404-408, doi: 10.2307 / 1366967 .
  13. ^ Paul H. Baldwin: The Life History of the Laysan Rail. In: The Condor. Vol. 49, no. 1, January / February 1947, pp. 14-21, doi: 10.2307 / 1364423 .
  14. ^ SA Trewick: Flightlessness and phylogeny amongst endemic rails (Aves: Rallidae) of the New Zealand region. In: Phil Trans. R. Soc. Lond. B. 352, 1997, pp. 429-446.
  15. ↑ Ellen E. Paxinos, Helen F. James, Storrs L. Olson, Michael D. Sorenson, Jennifer Jackson: mtDNA from fossils reveals a radiation of Hawaiian geese recently derived from the Canada goose (Branta canadensis).