There are around 10,000 species of birds in the world, and many millions of animals. However, not all are equally different, some are clearly more closely related than to others, reflecting a shared evolutionary history. In order to make sense of this diversity, biologists have devised an hierarchical system of classification to order species into groups, both to group similar species, and to reflect their evolutionary relationships.
Organisms are currently grouped into five great Kingdoms: the Monera essentially bacteria and blue-green algae, the Protista most unicellular organisms, the Fungi, the Plantae and the Animalia. Within the Animalia, there are 21 Phyla, each with a different body plan (e.g. the earthworms Annelida, the insects and allies Arthropoda, and the veterbrate animals, i.e. those with backbones Chordata). The birds (Aves) represent a Class within the Chordata, along with mammals, fish and others. For fuller details on how things are classified, explore the Tree of Life.
The 9,800 or so species of birds which are still living are arranged into 28 orders and, within these, around 172 families. Because we are re-constructing an unknown past from an often incomplete fossil record, there is still some disagreement over the precise order in which species evolved, and which are most closely related to each other. The divisions used here are relatively traditional, new research, particularly based on DNA studies may alter them in the future.
The first animals with bird-like features (feathers and a wishbone) evolved around 150 million years ago (in the early Cretaceous) from reptile stock. Archaeopteryx lithographica, of which fossils were dicovered in Bavaria, Germany in the 1861, is by far the most well-known of these and the first to be discovered. Quite how well Archaeopteryx could fly is a matter of some debate, it was probably an animal of wooded areas capable of at least of gliding and weak flapping, but probably not of long, sustained flights. Birds diversified through the Cretaceous period (145 - 65 million years ago) with Hesperornis (a diving seabird) and Ichthyornis, a tern-like bird, perhaps the best-known examples. These early birds were still quite reptile-like (for example they had teeth) and they disappeared at the end of the Cretaceous, along with the dinosaurs.
Modern birds arose around 60 million years ago, and are divided into two broad lineages, the Palaeognathes (including the ostrich and tinamous) and the Neognathes (everything else!), based on fundamental anatomical differences. Within the latter group the Passeriformes (perching-birds) are by far the largest order (over 5,000 species) and it is also one of the most recent, with most Families within it probably arising sometime in the Mid Tertiary (around 30-50 million years ago). The passerines are divided into two large sub-orders, the sub-oscines (Tyranni, around 1,000 mostly Southern Hemisphere species) and the oscines (Passeres), or songbirds, based on anatomical differences, such as the structure of the voicebox. It is thought they evolved in Gondwanaland (the Southern Hemisphere land-mass from which Australia, South America, Africa and Antarctica are derived). New species of bird are still being found (mostly in tropical regions) and, of course, some are going extinct (again, mostly in the tropics, where species' ranges tend to be smaller).
For a survey of the world's birds try the excellent New Encyclopedia of Birds edited by Chris Perrins (Oxford University Press, 2003).
English and Scientific Names
All species on the British List, i.e. those species that have occured naturally in a wild state or which have been introduced but maintain self-supporting feral populations are covered together with some additional species, mostly common escapes. Full accounts are provided for the 258 regularly occurring species, the remaining species have shorter accounts. For more details on the British List see Parkin & Knox (2007) and the latest (8th) Checklist.
With the increasing interest in birdwatching around the world, there is some debate on English names, particularly in Britain where calling a species 'Jay' can be seen as unhelpful, since there are at least 45 other species of Jay around the world. Increasingly, there is a move towards 'standardised' English names usually by adding appropriate epithets to the names more commonly used colloquially such as Gill & Wright 2006). In general, BTO uses the colloquial name, except where confusion may result (e.g. Lesser Redpoll). We have also given the 'standardised' name and other proposed alternative names; more local names are given separately (see below).
In order that people may refer unambiguously to a particular species a system of names (in Latin, the then current language) was proposed by Carl von Linné (usually known by the Latinised form of his name, Carolus Linnaeus) in the 1750s. Previously, species were described by, often extended, paragraphs describing their attributes, with little standardisation. Linnaeus invented the binomial system of nomenclature. Each species was given a name of two parts: a generic name, which refers to a small group of closely related species, and a specific name, which uniquely identifies the species. A third name is sometimes added to identify separate populations or races within a species, if these are identifiable. Each species thus has a name which is both unique to itself, and which reflects to some extent its evolutionary heritage, thus the Teal is known by its scientific name of Anas crecca. With the generic Anas indicating a group of closely related dabbling ducks and the specific crecca being inspired by its call. Note that although this name is in Latinised form, they may come from any language (crecca derives from the Swedish word kricka, so it is more correct to refer to a species' scientific name than to its "Latin name". Conventionally (as with any phrase in a foreign language) this is presented in italics, with the generic name (only) capitalised. To completely specify which species is referred to, the authority who proposed the name (and year the name was published) should also be given, in principle enabling anyone to find the original description. We have given these in [square brackets] after the scientific name. The rules governing the naming of a species are complex, and are overseen by the International Code for Zoological Nomenclature.
Many species, particularly the more conspicuous and common ones, have had a number of names in English, some of which are widely used, some more local and many which have only be used historically (Victorian naturalists, in particular, were good at coming up with new variants). We have given a small selection of the more typical ones which have actually been used in real parlance; for many species there will be several other variations around these themes. These have come from a variety of sources, but Greenoak (1997) and Buczacki (2002) were particularly useful. For those species where there is a (reasonably) established collective noun we given this, though most of these again originate with the Victorians and some are used more frequently than others.
Many species occur in different forms, known as races or subspecies. There is often some disagreement as to whether a particular form should be classified as a sub-species or as a species (see Helbig et al. 2002 for a full discussion). We list all the subspecies of each species that have officially been recorded in Britain (though note that some subspecies may not be distinguishable in the field). Subspecies that are endemic (or nearly so) to Britain or Ireland, that is they occur only there, are highlighted in bold. We give an estimate of the number of subspecies identified for the species, largely taken from Dickinson et al. (2003); for some species, particularly those that also occur in the less ornithologically studied parts of the world, this may essentially be a best guess. Where a species is noted as 'Monotypic', no distinct subspecies have been identified.
The components of the scientific name are usually descriptive of the species and although Latin in form may derive from any language (and actually most Latin words can also be traced to Greek antecedents). We give an indication of the most plausible derivation of each scientific name, based largely on Jobling (1991). Usually we note the verb (in the infinitive) from which a noun or adjective derives.
Codes for species are useful in a number of ways, particularly for recording observations in the field, and later for entering and storing data in the computer. Standard species codes also help ensure comptability between different recording systems enabling data to be exchanged between individuals and organisations seamlessly.
BTO 2 Letter Code
This is designed primarily for use in the field as a quick way of recording a species on maps. For common species the second 'letter' is a dot to represent a blank space, e.g. Blackbird is 'B.'. As there are a relatively limited number of combinations possible, codes are only available for species regularly occurring in Britain.
BTO 5 Letter Code
This code is used primarily by the British and Irish ringing scheme, and provides a codes for each species occurring in Britain (and can be extended to cover species abroad). In general, the code is formed from the first three letters of the first name and first two letters of the second name (e.g. BEArded TIt), but there are some exceptions.
This is a numeric code used by ringing schemes throughout Europe for data exchange, see the EURING website for more information. Each species is assigned a five digit number. The last digit is generally zero, being reserved for different subspecies (e.g. Southern Grey Shrike Lanius excubitor meridionalis is 15203). Thus, when a taxon is elevated to species rank (as in the case of the Southern Grey Shrike) there is no need to change the number.
Buczacki, S. 2002. Fauna Britannica. Hamlyn, London.
Dickinson, E.C. 2003. Complete checklist of the birds of the world. Helm, London.
Gill, F. & Wright, M. 2006. Birds of the world: recommended English names. University Press, Princeton.
Greenoak, F. 1997. British birds: their folklore, names and literature. Helm, London.
Helbig, A.J., Knox, A.G., Parkin, D.T., Sangster, G. & Collinson, M. 2002. Guidelines for assigning species rank. Ibis 144:518-525.
Jobling, J. 1991. A dictionary of scientific bird names. University Press, Oxford.
Parkin, D.T. & Knox, A.G. (2010) The status of birds in Britain & Ireland. Christopher Helm, London.
One bird, twelve journeys, 60 000 miles and invaluable scientific data: PJ the Cuckoo has left an incredible legacy.