3 - Specification and systematics are important components of biology:

The species is the unit used to describe animals. Animals belonging to the same species reproduce and are therefore separate from other species. The hereditary characteristics (genes) thus remain within the species. They are only exchanged between individuals belonging to the same species. It is a fact that species that sometimes live thousands of kilometres apart show great similarities. This is evident in so-called twin species, which are different species that have great external similarities. In parts of Europe, the tree creeper and the taiga tree creeper occur side by side. Both species are almost identical in appearance and ecological preference. Their song is the distinguishing feature that determines reproduction. This also occurs in other twin species, such as the chiffchaff and the willow warbler, the goldcrest and the firecrest, the northern nightingale and the nightingale, the glossy-headed warbler and the marsh warbler, the Common Tern and the Arctic Tern, the Great Spotted Woodpecker and the Syrian Woodpecker, the Collared Flycatcher and the Pied Flycatcher. Speciation refers to the process by which new species arise through evolutionary changes. This can occur through geographical isolation, adaptations within the same region or other mechanisms that lead to genetic differentiation. If a good genetic barrier has developed, interbreeding will no longer take place. The rule that animals belong to the same species if they can successfully reproduce with each other is then no longer met, and from that moment on, two species exist. Like the Tree Creeper and the Taiga Tree Creeper, the original species was split into two new ones due to the isolation of a number of populations during one of the ice ages in Central Europe. After that ice age, the birds reappeared in each other’s environment. So far, no hybrids have been discovered. The condition for the emergence of new species has therefore been met. Subspecies arise more quickly in any case. A frequently cited cause is climate change. Another possibility is a change in song and the response of conspecifics. An isolated population that, for whatever reason, starts singing differently can give rise to new species. Perhaps the tendency of songbirds to split into all kinds of orders is the basis for their enormously diverse and species-rich development.

Systematics, on the other hand, focuses on classifying and organising organisms based on their evolutionary relationships. This includes identifying, naming and categorising species in a hierarchical system, such as genera, families and orders. Together, speciation and systematics provide a fundamental framework for understanding and studying the diversity of life.

As the above has shown, the classification of birds is sometimes quite subjective. All researchers agree that no attempt at classification has been completely successful. Even the number of species currently living cannot be determined with certainty. The numbers reported by different authors vary from 8,700 to 9,000. The number is not fixed because there is a difference of opinion about the classification of some species. In addition, species become extinct and new ones are still being discovered. The classification into orders also differs among various authors. The number varies between 26 and 50. The lowest number is accepted as correct by most ornithologists. Based on the work of H.E Wolters: ‘Die Vogelarten der Erde (1975)’

The classification of the class of birds (Aves):

Order 1 Tinamiformes (Tinamiforms)
Order 2 Rheiformes (Rheas)
Order 3 Struthioniformes (Ostriches)
Order 4 Casuariiformes (Cassowaries)
Order 5 Apterygiformes (Kiwis)
Order 6 Podicipediformes (grebes)
Order 7 Gaviiformes (seabirds)
Order 8 Spenisciformes (penguins)
Order 9 Procellariiformes (storm petrels)
Order 10 Pelecaniformes (pelicans)
Order 11 Ciconiiformes (Herons)
Order 12 Phoenicopteriformes (Flamingo-like birds)
Order 13 Anseriformes (Ducks)
Order 14 Falconiformes (Birds of prey)
Order 15 Galliformes (Galliform birds)
Order 16 Gruiformes (Crane-like birds)
Order 17 Charadriiformes (Wading birds)
Order 18 Columbiformes (Pigeon-like birds)
Order 19 Psittaciformes (Parrot-like birds)
Order 20 Cuculiformes (Cuckoo-like birds)
Order 21 Strigiformes (Owl-like birds)
Order 22 Caprimulgiformes (Nightjars)
Order 23 Apodiformes (Swifts)
Order 24 Coraciiformes (Rollers)
Order 25 Piciformes (Woodpeckers)
Order 26 Passeriformes (Songbirds)