Classification of birds

RSS

Classification of birds

Classification of birds

The basic unit of taxonomy is species. The term species is defined as a group of individual organisms that are capable of mating and reproduction in nature but not with members of other similarly defined species. They can also be defined by genetic similarity and stability. In some cases, species can interbreed, but since they are sufficiently isolated ‒ geographically, genetically or because of their behaviour, they cannot normally form hybrids that could permanently find their place in nature. Exceptionally, these limits can be overcome and possibly even fertile hybrids can be born, so the definition of some species can sometimes appear as a difficult problem. Nevertheless, it should be mentioned that either in taxonomy or in systematics, the only biologically defined unit is species. All the other categories or units are artificially constructed more or less natural groups. Within species, we distinguish races based on geographical distribution (subspecies). Organisms belonging to different subspecies of the same species are capable of interbreeding and producing fertile offspring. However, they are usually geographically isolated, especially during the breeding season. Geographical areas of subspecies may sometimes overlap and form a transitional zone populated also by hybrids.

Species are assigned to a genus. Each species has a binomial scientific name. Scientific names have their Latinised forms and in texts, they are usually written in a different font, but they always are in Latin. The name of each species is unique and does not depend on local or national names.

Genera are grouped into families, with their scientific name having a suffix -idae. Families are grouped into orders that are identified by a suffix -formes in scientific terminology. Orders create classes. Birds (Aves) are an example of a class. Other categories such as suborder, subfamily or superspecies, along with others, are essential for systematics in order to define relationships between different groups in more detail. Even higher taxon, genus or family, can sometimes represent a single species only. In this case we refer to it as “monotypic”. Rules for nomenclature of birds are specified in the International Code of Zoological Nomenclature.

Systematic categories in Zoology

Regnum ‒ Kingdom

Phylum

Subphylum

(Divisio - Division)

(Subdivisio – Subdivision)

Superclassis – Superclass

Classis – Class

Subclassis – Subclass

(Infraclassis – Infraclass)

(Cohors – Cohort)

(Subcohors – Subcohort)

Infraordo – Infraorder)

Superfamilia – Superfamily

Familia – Family

Subfamilia – Subfamily

(Tribus – Tribe)

(Subtribus – Subtribe)

Genus

Subgenus

(Superspecies)

Species

Subspecies

Basic systematic categories are written in bold, additional categories are derived from the basic categories using prefixes super- or sub-; categories that are not normally used are written in parentheses. The prefix infra- denotes a level below the prefix sub-.

Taxonomy

Similarities between species may reflect their common origin, but similar adaptations may originate in a similar way of life. The latter phenomenon is called convergence and characteristics that appear in unrelated species just because of adaptations to the same conditions cannot be used for their classification. For the purposes of classification only characteristics reflecting evolution can be used, because it is only on this basis that natural relationship between species can be assessed. This classification is known as phylogenetic. The aim of modern taxonomy is to reveal evolutionary relationships between taxa. The most appropriate characteristics for this purpose are those relatively stable over time without tendency to change due to minor changes in the environment (that may lead to the above-mentioned convergence). For example, the size and shape of a beak or the length of legs are characteristics that do not prove that much in the classification of species. On the other hand, the slight variations in climate patterns, type of syrinx (the vocal organ of birds) or the comparison of DNA (deoxyribonucleic acid – the bearer of heredity) are incomparably more important in this process. Successful and proper classification ranks the successors of a common ancestor into the same group which can be called natural. It may also be partially determined by prediction. With the development of new laboratory procedures and methods, new characteristics (e.g. biochemical composition of feathers) can be taken into account. An analysis of mutual relations of species based on the appropriate selection of new characteristics should provide the same classification into groups, while the unnatural classification based on the incorrect selection of characteristics provides only a minimum or no congruence at all. When the new information is obtained this way, the classification may change and such situation sometimes requires a change in nomenclature as well. Even if the scientific names of birds were permanent, unlike national names, over time, there may arise a need for their alterations caused by the update of bird family relationships. This should by no means be seen as a "change for change’s sake", but as a result of a constant deepening of knowledge and a dynamic nature of taxonomy.

Passerines

When it comes to evolution, passerines are the most recent and advanced bird order. This order is estimated to group 3/5 of all living bird species (about 5,650 out of 9,700 species of 1,168 genera). Other birds such as Galliformes (chicken-like) belong to older and more primitive orders of birds. Passerines broke away from other, more primitive, orders and became the most successful bird order. They appeared in greater numbers after Paleogene period in unpopulated areas because of their highly adaptable way of life. Almost all contemporary scientists have considered Passerines to be of a monophyletic origin (they have a common ancestor) sharing similar anatomic and physiological features (a special type of palate and syrinx – a vocal organ, distinctive feet, faster metabolism...). Passerines can be divided into two broad groups: Suboscines and Oscines. Oscines, or “songbirds”, constitute about 4/5 of Passerines (about 4,500 species) and have rather uniform morphology while morphological uniformity of Suboscines (about 1,150 species) is not that stringent. In particular, we focus on Oscines, “songbirds”, here. These birds are unique for their homogeneous external features. Most of them are small birds that feed on insects, small fruits and grain ‒ seeds. Many differences can be seen in their feeding mechanism and beak shape that are rather convergent, they adapted to the environment, than indicative of any new evolutionary line. Small differences between individual orders and species of small songbirds support the theory that they are evolutionary recent species (from roughly mid-to-late Tertiary period).

Systematic classification of the Gouldian Finch

Biologists (systematists) assign names to animals in order to avoid possible confusion. Therefore, each species is assigned two names, a generic name and a specific epiteth. In Latin binomial nomenclature, genus is always given as first with a capital letter. A specific epiteth follows a generic name and is always written with a small letter.

A specific epiteth is often a name of a discoverer of species, or the name may refer to characteristics of an animal (plumage colouration, body shape, habits, geographical location...). Sometimes a third name that corresponds with the subgenus is added and it is assigned to an animal at the same principle as a second name. The first name Amadina covered the similarities that John Gould found in some African birds feeding on seed (Amadina erythrocephala ‒ Red-headed Finch). However, this name was in use for a short period of time since it was based on superficial similarities only. Given the similarities of characteristics (shape of the tail and beak), another classification was into genus Poephila, based on recent research ‒ comparisons. The name Erythrura gouldiae (Gouldian Finch) is often used in some circles. According to observations, it was placed in the genus Erythrura based on the following facts:

- They inhabit tree-holes during the breeding season.

- Brood have papillae around their beaks.

- They have a sharp outline around the mask.

- They can only interbreed with Erythrura trichroa ‒ Blue-faced Parrotfinch.

Many authors (Immelmann, Goodwin, Evans and Fidler) decided to use the genus Chloebia that has been promoted by Reinchenbach since 1862, with Gouldian Finch as the sole representative of the genus. The name of this genus is based on the number of differences found in the behaviour and external features between Parrotfinches and Finches. John Gould described this magnificent bird and named it in memory of his wife as The Lady Gouldian Finch. Later shortening of the name resulted in modern nomenclature ‒ Gouldian Finch.

Genus Chloebia contains only one species ‒ Gouldian Finch, as already mentioned. It belongs to the family Estrildidae (Estrildid Finches) with 29 genera and 133 species (Gosler). Although John Gould placed Gouldian Finch in the genus Lonchura, this concept was not used too much. Reichenbach (1862) claimed that this species should belong to the genus Chloebia. In 1943, Dr. Jean Delacour (in Zoologica magazine, Issue 38) was for its classification to the genus Poephila. Some experts later placed Gouldian Finch in the genus Erythrura.

Explorers Immelman and D. Goodwin agree that a kinship of Gouldian Finch with other genera is negligible or has not been proven yet. For this reason, they decided that the best solution would be to create a separate genus for Gouldian Finch ‒ Chloebia (Reichenbach, 1862).

I'll also stick with the name Chloebia Gouldiae (Gouldian Finch).

There are 3 varieties of Gouldian Finches characterized by heads of different colours. First described species were Red-headed finches. A few years later, Black-headed finches, initially considered females, were seen. Later, a small number of finches with yellow (orange) colour of their heads were discovered.

Classification of Gouldian Finch in zoology

Domain...................................... Eukaryotes

Regnum – Kingdom................ Animalia

Subkingdom.............................. Eumetazoa

Branch....................................... Bilateria

Phylum...................................... Chordata

Subphylum................................. Vertebrata (Vertebrates)

Superclassis – Superclass

Classis – Class.......................... Aves (Birds)

Subclassis – Subclass............... Ornithurae (″true birds″)

Superordo – Superorder........... Neognathae (Neognaths)

Ordo – Order.............................. Passeriformes (Passerines)