How do birds fit into the study of all living things, and how are they classified?
The standard method for classifying living things is to group them together into categories that define them according to features that they share and which set them apart from other categories. This method gives rise to an increasingly detailed set of categories that been given standard names, although these are not universally agreed and changes to them have been made at various times.
According to one commonly agreed method, birds belong to the kingdom of animals, the phylum of chordata (animals having spinal cords) and the subphylum of vertebrata (animals with backbones).
(Song thrush – Turdus philomelos)
They then form their own class, namely that of aves. A special subclass has been assigned to Archaeopteryx, the long-extinct feathered reptile that has been thought to be the earliest bird (although this is disputed), which leaves all other birds in the subclass of neornithes.
The bird world is then split into about 30 groups that are designated as orders, and these are further divided into a total of around 200 families. Further divisions are into genus and species, of which there are more than 10,000, with in excess of 20,000 subspecies.
(Great skua – Stercorarius skua)
An example of an order is passeriformes, which includes all perching birds. This contains more than 70 family groups and has more species than all the other bird orders put together.
A species is defined according to whether individual members can mate and produce offspring that will themselves be fertile. Sometimes it is necessary to define sub-species where there are distinctions between populations (often geographically remote from each other) but which are still capable of interbreeding.
(Egyptian goose – Alopochen aegyptiacus)
As with all living species, birds are classified according to invented Latin names that consist of a genus and a species (and sometimes sub-species). Examples include Parus major (great tit) and Hirundo rustica (swallow).
(All photos were taken by me)