**1. Introduction**

Apparently, humans always tried to classify the animals, which they saw or hunted. They gave them local names. Only during the time of classical Greek scholars, a more systematic approach emerged. The first scholar was Aristotle (384–322 BC), the known father of Natural history and Science. He described the appearance, behavior, and occurrence of more than 140 bird species [1–3]. The next progress came with Plinius (23–79 AC), a known Roman writer. Plinius analyzed the form of feet and legs to classify birds in his *Historia naturalis*. Aristotle and Plinius were the main sources of information until the Renaissance (from 1400 onwards). The Renaissance brought progress in many fields of science, including ornithology. New knowledge was no longer transmitted in hand-written books but in printed books when Johannes Gutenberg in Mainz (Germany) invented book printing around 1450 [1–3]. In consequence, many illustrated books on

plants and animals were published. William Turner (1500–1568), Conrad Gessner (1516–1565), and Pierre Belon (1517–1564) were three known ornithologists in the 16th century. Gessner reported on 180 bird species in the illustrated *Historia animalium.* John Jonston (1603–1675) published the *Historiae naturalis de avibus libri VII* in 1650 illustrated by Matthaeus Merian (**Figure 1**). However, the classification was only based on morphology, leading to wrong relationships. As can be seen from **Figure 1**, bats were included in birds and the cuckoo and shrike were treated as raptors.

After 1600, the ornithological landscape quickly changed. New species were brought in from everywhere in the world by early explorers, and systematic collections of specimens were started facilitating the study of avian taxonomy. Known ornithologists of the 17th century were Walter Charleton (1619–1707), John Ray (1628–1704), and Francis Willughby (1635–1672). John Ray became famous since he produced with *Ornithologiae libri tres* a first modern ornithology handbook, based it on authentic observations [4].

Another breakthrough came in the 18th century: Carl Linnaeus (1707–1778), a naturalist and medical doctor from Uppsala (Sweden) revolutionized taxonomy by introducing a binary nomenclature, in which every animal and plant species obtained its own and unequivocal Latin name [1–3]: The Chaffinch was called *Fringilla coelebs* L.; the first name indicates the genus and the second the species. This name is exclusive for the Chaffinch. By comparing the outer morphology of animals and plants, Linné arranged species with a similar anatomy and morphology into genera, orders and classes. For birds, Linné used the morphology of feet and beaks to distinguish six orders of birds, which included 85 genera. As there are several

#### **Figure 1.**

*Illustrations from* Historiae naturalis de avibus libri VII*. As can be seen, shrikes and cuckoo were grouped with raptors because of their bill morphology. Cuckoo = Cuculus; shrike = Lanius; raptors = Tinnunculus, Dendrofalcus (a) and even bats were classified as birds because of their wings. Nycticorax= Night Heron; Caprimulgus = Nightjar; Bats= Fledermaus (b). (photo M. Wink).*

**5**

*DNA Analyses Have Revolutionized Studies on the Taxonomy and Evolution in Birds*

larks, humming birds, nightjars, swifts, crossbills, wagtails, and tits [1].

events of convergent evolution, some of his systematic assumptions were wrong and could not survive. In the 10th edition of *Systema naturae* (1758), six orders were distinguished: 1. **Accipitres**: Raptors, owls, parrots, waxwings, and shrikes; 2. **Picae**: Woodpeckers, hornbills, cuckoos, hoopoes, birds of paradise, crows, and creepers; 3. **Anseres**: all water birds, pelicans, cormorants, loons, grebes, gulls, and terns; 4. **Grallae**: Ratites, waders, flamingos, storks, herons, cranes, coots, and bustards; 5. **Gallinae**: wild fowl, guans, grouse, and quails and 6. **Passeres**: Pigeons, thrushes,

During the 18th and 19th century, the knowledge on taxonomy and systematics of birds rapidly increased. Many explorers and travelers explored Europe, Africa, Asia, Australia and the Americas, and brought back many unknown species. Taxidermy improved [5] and specimens could be stored in skin collections, which were then created in Paris (1793), London (1881), Frankfurt, Halle, Munich, and Dresden [1, 2]. These curated collections enabled a better comparison and study of related and unrelated taxa. Already at that time, the status of species and subspecies

The 19th century was strongly influenced by the new concept of evolution and phylogeny through natural selection formulated by Charles Darwin (1809–1882) and Alfred Russel Wallace (1823–1913). Species were no longer considered to be unchangeable (or created by God) but were seen in a phylogenetic context. This means, ancestral taxa had existed from which the extent taxa derived. Charles Darwin came up with the concept of a phylogenetic tree, which can illustrate the

After Darwin, ornithologists overturned the typological species concept and tried to build up a "natural system", based on shared ancestry and comment descent. According to [6, 7], more than 40 classifications were proposed during the last two centuries. Since 1900, the order of bird families in handbooks and field

Traditionally, morphology, such as plumage, beak and head shape, had been used to make inferences in systematics and taxonomy [1, 3]. Since 1900 new characters were included, coming from ecology, biogeography, and biochemistry. The main concept of classification remained overall similarity; the more similar two

Whereas the inclusion of similar taxa into a common genus was mostly unambiguous, the circumscription of families and orders was however more difficult. In many taxa, a variation of plumage can be seen in relation to age, sex or season. Large skin collections were helpful to find out if the variable forms belonged to a single species. Several bird species (e.g. ducks and geese) can hybridize, which generate more confusion. We already noticed that adaptive characters can occur convergently. In consequence, similar adaptive features might have evolved in unrelated group of taxa. If such adaptive characters are used for taxonomy, artificial and polyphyletic groups (clades with members from unrelated lineages) may be created (**Figure 1**). Over the last 200 years, different species concepts have also strongly influenced taxonomy and systematics [3, 4, 10]. Although ornithologists loved the typological species concept for a long time, it was substituted by Ernst Mayr by the Biological Species Concept (BSC). Presently, the "Phylogenetic Species Concept (PSC)" has

The German entomologist Willi Hennig (1913–1976) introduced the concept of cladistics. He distinguished plesiomorphic, apomorphic and synapomorphic traits

*DOI: http://dx.doi.org/10.5772/intechopen.97013*

was extensively debated.

descent from common ancestors [1–3].

**2. Towards a new avian classification**

taxa, the more closely related they should be.

guides was based on these classification systems [8–12].

been widely accepted, because it better fits the molecular data [1].

#### *DNA Analyses Have Revolutionized Studies on the Taxonomy and Evolution in Birds DOI: http://dx.doi.org/10.5772/intechopen.97013*

events of convergent evolution, some of his systematic assumptions were wrong and could not survive. In the 10th edition of *Systema naturae* (1758), six orders were distinguished: 1. **Accipitres**: Raptors, owls, parrots, waxwings, and shrikes; 2. **Picae**: Woodpeckers, hornbills, cuckoos, hoopoes, birds of paradise, crows, and creepers; 3. **Anseres**: all water birds, pelicans, cormorants, loons, grebes, gulls, and terns; 4. **Grallae**: Ratites, waders, flamingos, storks, herons, cranes, coots, and bustards; 5. **Gallinae**: wild fowl, guans, grouse, and quails and 6. **Passeres**: Pigeons, thrushes, larks, humming birds, nightjars, swifts, crossbills, wagtails, and tits [1].

During the 18th and 19th century, the knowledge on taxonomy and systematics of birds rapidly increased. Many explorers and travelers explored Europe, Africa, Asia, Australia and the Americas, and brought back many unknown species. Taxidermy improved [5] and specimens could be stored in skin collections, which were then created in Paris (1793), London (1881), Frankfurt, Halle, Munich, and Dresden [1, 2]. These curated collections enabled a better comparison and study of related and unrelated taxa. Already at that time, the status of species and subspecies was extensively debated.

The 19th century was strongly influenced by the new concept of evolution and phylogeny through natural selection formulated by Charles Darwin (1809–1882) and Alfred Russel Wallace (1823–1913). Species were no longer considered to be unchangeable (or created by God) but were seen in a phylogenetic context. This means, ancestral taxa had existed from which the extent taxa derived. Charles Darwin came up with the concept of a phylogenetic tree, which can illustrate the descent from common ancestors [1–3].
