Information about Alula

This article is about the Alula feather. For the Finnish ornithological journal of the same name, see Alula (journal); for the Hawaiian plant, see Brighamia insignis.

The alula, or bastard wing, is a small projection on the anterior edge of the wing of modern (and some ancient) birds. It is actually one of the bird's digits, and is typically covered with three to five small feathers, with the exact number depending on the species. Like the larger flight feathers found on the wing's trailing edge, these alula feathers are asymmetrical, with the shaft running closer to anterior edge.

Function

In most situations, the alula is held flush against the wing; however, it can be manipulated. When flying at a slow speeds or landing, the bird moves its alula slightly upwards and forward, which creates a small slot on the wing's leading edge. This functions like the slot on the wing of an airplane, helping to smooth the flow of air over the wing's upper edge, reducing turbulence and thus helping to increase lift.^[1] Without this action, the bird would be at risk of stalling (and thus falling out of the sky) in such situations.

Alula in ancient birds

The presence of an alula has been confirmed in several now-extinct ancient relatives of modern birds, including Eoalulavis hoyasi (an enantiornithine from the mid-Cretaceous, 115 ^[2] mya) and the earlier Protopteryx fengningensis.^[3] Since these species are not closely related to modern birds, either the alula evolved twice, or it did so more than 130 mya.

Alula in flies

In flies (Diptera), the alula is a lobe of the posterior margin of the wing bounded proximally by the upper calypter, distally by the axillary incision, and anteriorly by the base of the anal vein. The term has also been applied to the upper and lower calypters collectively.

See also

• Bird flight

Citations

References

• id="CITEREFEhrlichDobkinWheyePimms1994">Ehrlich, Paul R; David S. Dobkin & Darryl Wheye et al. (1994), The Birdwatcher's Handbook, Oxford University Press, ISBN 0-19-858407-5
  • id="CITEREFSanzChiappePérez-MorenoBuscalioni">Sanz, J. L.; L. M. Chiappe & B. P. Pérez-Moreno et al. (1996-08-01), "An Early Cretaceous bird from Spain and its implications for the evolution of avian flight", Nature 382: 442-445
    • id="CITEREFZhangZhou">Zhang, Fucheng & Zhonghe Zhou (8 December 2000), "A Primitive Enantiornithine Bird and the Origin of Feathers", Science 290 (5498): 1955-1959, DOI 10.1126/science.290.5498.1955
      
      

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      Alula is an ornithological journal published in Finland. Although previously published in both Finnish and English, only the English language edition is currently produced. It is aimed primarily at birders with an interest in the birds of the Western Palearctic.
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      B. insignis
      
      Binomial name
      Brighamia insignis
      
      Brighamia insignis (Hawaiian alula) is an endangered species of Hawaiian lobelioids, native to the island of Kauai.
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      Anterior can refer to:

      • Anterior and posterior, both Anatomical terms of location
      • Anterior (band), A Welsh Metal band

      
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      WING
      
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      Aves
      Linnaeus, 1758
      
      Orders
      
      About two dozen - see section below
      
      Birds (class Aves) are bipedal, warm-blooded, egg-laying vertebrate animals.
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      A finger is a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates. Normally humans have five digits on each hand (exceptions are polydactyly, hypodactyly and digit loss).
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      Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds. They are the outstanding characteristic that distinguishes the Class Aves from all other living groups. Other Theropoda also had feathers (see Feathered dinosaurs).
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      species is one of the basic units of biological classification. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring.
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      flight feather refers to any of the long stiff feathers on the wing or tail of a bird; those on the wing are called remiges (singular remex) while those on the tail are called rectrices (singular rectrix).
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      fixed-wing aircraft is a heavier-than-air craft where movement of the wings in relation to the aircraft is not used to generate lift. The term is used to distinguish from rotary-wing aircraft, or ornithopters, where the movement of the wing surfaces relative to the aircraft
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      The lift force, lifting force or simply lift is a mechanical force generated by solid objects as they move through a fluid.^[1]
      
      While many types of objects can generate lift, the most common and familiar object in this category is the airfoil, a
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      For other uses, see stall.

      
      
      In aerodynamics, a stall is a sudden reduction in the lift forces generated by an airfoil. This most usually occurs when the critical angle of attack for the airfoil is exceeded.
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      extinction is the cessation of existence of a species or group of taxa, reducing biodiversity. The moment of extinction is generally considered to be the death of the last individual of that species (although the capacity to breed and recover may have been lost before this point).
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      Neornithes
      Gadow, 1893
      
      Superorders
      
      Paleognathae
      Neognathae
      
      Modern birds (subclass Neornithes) are the members of class Aves that have survived into recent times and have coexisted with humans.
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      Eoalulavis
      
      Eoalulavis was an enantiornithine bird. It lived during the Early Cretaceous, about 115 mya ^[1] and is known from fossils found at Las Hoyas, Spain ^[2].
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      Enantiornithes
      Walker, 1981
      
      Orders
      
      see text
      Synonyms
      
      Enantiornithomorpha
      Chiappe, 1999

      Enantiornithes

      Enantiornithes is an extinct group of flying Protobirds.
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      The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i.e. from 145.5 ± 4.0 million years ago (Ma)) to the beginning of the Paleocene epoch of the Tertiary Period (about 65.5 ± 0.3 Ma).
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      mya or "m.y.a." is an abbreviation for million years ago. This abbreviation is commonly used as a unit of time to denote length of time before the present or "B.P." (before AD 1950). Specifically, one mya is equal to 10⁶ years ago.
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      species is one of the basic units of biological classification. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring.
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      Diptera
      Linnaeus, 1758
      
      Suborders
      
      Nematocera (includes Eudiptera)
      Brachycera
      
      True flies are insects of the Order Diptera (Greek: di = two, and pteron
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      In sciences dealing with the anatomy of animals, precise anatomical terms of location are necessary for a variety of reasons. Non-scientists often wonder why zoological and human anatomists use complex terminology to describe locations on a body, when common terms like "up",
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      A calypter is either of two posterior lobes of the posterior margin of the forewing of flies between the extreme posterior wing base and the alula, which covers the halteres.
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      In sciences dealing with the anatomy of animals, precise anatomical terms of location are necessary for a variety of reasons. Non-scientists often wonder why zoological and human anatomists use complex terminology to describe locations on a body, when common terms like "up",
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      Flight is the main mode of locomotion used by most of the world's bird species. It assists birds while feeding, breeding and avoiding predators.

      Evolution and purpose of bird flight

      
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      Nature is a prominent scientific journal, first published on 4 November 1869. Although most scientific journals are now highly specialized, Nature is one of the few journals, along with other weekly journals such as Science and
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      Aves
      Linnaeus, 1758
      
      Orders
      
      About two dozen - see section below
      
      Birds (class Aves) are bipedal, warm-blooded, egg-laying vertebrate animals.
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      Bird anatomy, or the physiological structure of birds' bodies, shows many unique adaptations, mostly aiding flight. Birds have evolved a light skeletal system and light but powerful muculature which, along with circulatory and respiratory systems capable of very high metabolic
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      Flight is the main mode of locomotion used by most of the world's bird species. It assists birds while feeding, breeding and avoiding predators.

      Evolution and purpose of bird flight

      
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      In most birds and reptiles, an egg (Latin ovum) is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo.
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