The past few decades have seen a revolution in bird systematics – the study of bird relationships. Molecular techniques assessing genetic differences between species have forced some radical changes in the way we think birds evolved – and hence the way we classify them. This process is ongoing, but sufficient consensus has emerged for several field guides and bird books to take the plunge and adopt the new order. Peter Ryan explains some of the major changes.

iologists attempt to classify birds Evolutionary relationships can be and other organisms in a hier­ inferred from the pattern of shared Classifying birds Barchy that reflects their evolution­ derived characters – features common to ary relationships. This is termed natural a group that are not shared with more Every species is placed in a hierarchical classification, and implies that species in distantly-related species. The trick is to structure that should reflect its evolutionary the same genus are more closely related identify which sets of characters con­ history. For example, the Black-winged Stilt to each other than those in other gen­ vey a meaningful evolutionary signal. is classified as follows: era, and that families in the same order Many birds share the same character­ are more closely related to each other istics simply because they live in the Domain: Eukarya (as distinct from Prokarya, than to other families, etc. There are same environment or feed on the same the bacteria and archaebacteria) other ways to group birds – by colour, type of food. This is termed convergent Kingdom: Animalia (as distinct from Plantae, size or even alphabetically – but these evolution. Relationships are also con­ Fungi and Protista) are artificial classifications which, albeit founded by reversals in character states, useful for some purposes, are imposed whereby some of a related group of Phylum: Chordata (as distinct from all the rather than inherent. The advantage of organisms have reverted to the ancestral invertebrate phyla) using a natural classification system is condition. Class: Aves (all birds, although strictly birds that it tells us about the fundamental Initial attempts to infer the relation­ are a subset of dinosaurian reptiles) relationships among birds. The main ships among birds were based largely on disadvantage is that as our knowledge their shape and structure, but it soon Order (-iformes): Charadriiformes (waders, improves, so the classification is likely to became apparent that characters subject gulls, terns, auks and sandgrouse) change. Such changes have even taken to selection for immediate survival, such Family (-idae): Recurvirostridae (avocets and place at the highest levels of classifica­ as bill, wing and leg shape, carry little stilts) tion. Whereas there used to be two king­ deep evolutionary signal. Focus then doms of organisms, animals and plants, switched to more conserved characters, Genus: Himantopus (the stilts) we now recognise six kingdoms, divided such as bones, muscles and other inter­ Species: himantopus (the Black-winged Stilt) into two domains. nal structures. These formed the basis Orders and families take their names for the classification of birds into orders from one of their typical genera, but and families, whereas external appear­ are distinguished by specific suffixes: ance and structure were used to group relationships. Different genes evolve at -iformes for orders and -idae for families. similar species into genera. different rates, providing biologists with Other levels in the hierarchy may be Bird taxonomy was hotly debated a toolkit they can use to assess the rela­ recognised, such as Superfamily (-oidea), during the late 19th and early 20th tionships among all levels of life. For the Subfamily (-inae) and Tribe (-ini, between centuries, but a fairly stable order was most part, the new genetic evidence has subfamily and genus). Sometimes the established by the 1950s, reflecting at supported the relationships among birds, level at which a group is pegged is best a consensus based on the available at least at the level of orders, but there debatable. For example, the avocets and evidence, or at worst a compromise have been some major changes in the stilts are often treated as a subfamily between opposing factions. This resulted relationships among and within orders. Recurvirostrinae of a more in­clusive in the familiar sequence in which birds Charadriidae, the plovers and lapwings. were listed in bird books. Sibley’s ‘tapestry’ The past few decades have seen a Charles Sibley devoted much of his revolution in taxonomy thanks to the career to using molecular markers to The unique structural adaptations for development of techniques that detect infer evolutionary relationships. During life as a flightless, wing-propelled diver and analyse differences among organ­ the 1980s he used a relatively crude resulted in penguins being placed at the isms in the most fundamental building technique called DNA-DNA hybridisa­ start of the sequence of modern birds, blocks of life – their genes. Because most tion to conduct pair-wise comparisons

TONY CAMACHO but they don’t reflect the penguins’ genes mutate at random, they provide between the DNA of birds from virtually true relationships. power­ful tools for inferring evolutionary all major groups. Together with Jon 

66 bird systematics africa – birds & birding august/september 2005 bird systematics 67 Ahlquist, he amassed enough informa­ Bird) and the South American tinamous, Until recently, it was assumed that the shorebirds and diurnal raptors are more tion to propose an entirely new view on are represented in Africa only by the break-up of Gondwanaland took place closely related than previously thought, avian relationships. ostriches. The striking similarity of the too long ago to have influenced the radia­ leading to the lumping of several orders Sibley confirmed that the most basic large, flightless ratites in all the southern tion of the more modern neognaths, of birds. Indeed, Sibley and Ahlquist division among birds is between the continents suggests that they evolved despite intriguing similarities between advocate lumping them all into a single Palaeognathae (‘ancient jaws’) and on the ancient southern super-continent some widely scattered birds. For exam­ enlarged order, Ciconiiformes. Neognathae (‘new jaws’), which have Gondwanaland, which broke up dur­ ple, the flightless Kagu of New Caledonia Some orders proved not to be natural fundamentally different palate structures. ing the Cretaceous, about 120–85 million is surprisingly similar to the Sunbittern groups. Among the former Pelecani­ The former group, comprising the ratites years ago, to form Africa, Australia, South from Central and South America. The formes, characterised by four webbed (ostriches, emus, cassowaries and kiwis, America, Antarctica, Madagascar and the problem was that fossils, mainly from toes, cormorants, darters, gannets and as well as the extinct moas and Elephant Indian subcontinent. the northern hemisphere, suggest that boobies are closely related, but pelicans, modern birds only appeared approxi­ tropicbirds and frigatebirds are not. Struthioniformes (ostriches, rheas, emu, cassowaries mately 65 million years ago, imme­ Similar errors were detected at other and kiwis) Palaeo­ diately after the Cretaceous–Tertiary taxonomic levels. Families such as the gnathae Tinamiformes (tinamous) extinction which saw the demise of the cuckoos and barbets were split because peter ryan dinosaurs. However, differences in gene they are not natural groups, and new Craciformes (megapodes, curassows and guans) Gallo­ sequences suggest that the neognath light was shed on the long-debated Rheas, such as this Greater Rhea, bear a striking Galliformes (guineafowls, quail, pheasants and francolins) anserae orders diverged at least 80–90 million positions of several enigmatic taxa. For resemblance to ostriches, even though South America Anseriformes (screamers, ducks and geese) years ago, when the southern continents example, the Shoebill Balaeniceps rex is broke away from Africa some 110 million years ago. Turniciformes (buttonquail) were still close together. The appearance a derived pelican, and the New World of modern bird fossils in the northern vultures and condors are related to Piciformes (honeyguides, woodpeckers, barbets and toucans) hemisphere coincides with the collision storks, and are merely convergent with families: the Muscicapoidea (thrushes, structure. From an African perspective, Galbuliformes (jacamars and puffbirds) between the Indian plate and Asia some Old World vultures. fly­catchers, starlings and allies), the several unexpected relationships have Buceratiformes (hornbills) 65 million years ago. Perhaps the most exciting result was Sylvioidea (tits, larks, warblers, babblers, emerged. The elminias, a group of small, Upupiformes (hoopoes, woodhoopoes and scimitarbills) Within the neognaths, there are two the development of a framework for the bulbuls, white-eyes and allies) and the fan-tailed ‘flycatchers’, are merely con­ major groupings: a basal radiation largest avian order, the Passeriformes. Passeroidea (sunbirds, weavers, sparrows, vergent with the crested-flycatchers and Trogoniformes (trogons) of gamebirds and waterfowl, the Gallo­ With more than 5 700 species, pas­ pipits, canaries, buntings and allies). paradise-flycatchers of the Corvoidea, Coraciiformes (rollers, motmots, todies, kingfishers and anserae, with all remaining birds in the serines make up some 60 per cent of and fall within the Passerida. Together bee-eaters) Neoaves (‘new birds’). Among the Gallo­ the world’s birds. Traditionally, differ­ A tree of life for birds with the Asian Culicicapa flycatchers Coliiformes (mousebirds) anserae, only the Craciformes (mega­ ences in syrinx musculature and other Subsequent work using conserved and the Fairy Flycatcher, they form Cuculiformes (cuckoos, malkohas, coucals, Hoatzin, anis and podes, guans and currassows) are not structural differences have been used to nuclear gene sequences has refined a separate radiation allied to the tits. roadrunners) found in Africa. Both the Galliformes divide them into two groups: the sub­ some of Sibley and Ahlquist’s origi­ Livingstone’s Flycatcher and the other Psittaciformes (parrots, parakeets, lovebirds, lories, amazons and Anseriformes are well represented oscines (pittas, broadbills, asities and a nal conclusions, and a coherent pic­ Erythrocercus flycatchers apparently form and macaws) here, including an endemic family, host of Neotropical groups including ture of how the passerines evolved is a separate flycatcher-like radiation within Apodiformes (swifts) the guineafowls, Numididae. Previously, woodcreepers, antbirds, tapaculos, cot­ slowly emerging. The New Zealand the Sylvioidea. The nicators, which have v es penguins were placed at the start of the ingas, manakins and tyrant-flycatchers) wrens (Acanthisittidae) are basal to all been bounced back and forth between Trochiliformes (hummingbirds)

N eoa neognaths, but their peculiar morphol­ and the oscines. Among the oscines or other passerines, again emphasising the the bulbuls and bush-shrikes, belong Musophagiformes (turacos) ogy is merely an extreme adaptation to songbirds there has been no convincing importance of the southern hemisphere to neither group, apparently forming a Strigiformes (owls, nightjars, frogmouths, Oilbird and potoos) their diving lifestyle. In fact, they are structure, with convergence clearly con­ in avian evolution (at least as a refuge basal lineage within the Sylvioidea. And quite closely related to albatrosses and founding relationships among groups for relictual species). The fundamental one of the most bizarre results is that the Columbiformes (pigeons and doves) petrels, and more distantly to a suite of such as warblers and flycatchers. split into suboscines and oscines is sup­ sugarbirds, endemic to southern Africa, Gruiformes (bustards, mesites, seriemas, finfoots, rails, other waterbirds, including grebes, her­ Sibley and Ahlquist found that a ported, but all the oscines appear to appear to be basal to the Passeroidea, trumpeters, cranes, Limpkin, Sunbittern and Kagu) ons, storks and cormorants. diverse array of enigmatic passerines have arisen from the Australasian radia­ together with Spot-throat and Dapple- Charadriiformes (sandgrouse, thick-knees, sheathbills, plovers, The sequence of orders within the from Australasia are not the last gasp of tion, with the Passerida nested within throat, enigmatic forest understorey oystercatchers, avocets, stilts, jacanas, sandpipers, snipes, coursers, pratincoles, gulls, terns, skimmers, skuas and auks) Neoaves remains poorly resolved, pos­ boreal radiations, but rather are basal the Corvida. And within this radiation, ‘babblers’ confined to the Eastern Arc sibly because their initial radiation was forms of the original radiation of oscine some enigmatic African species have mountains of East–Central Africa. Falconiformes (Osprey, kites, fish eagles, vultures, hawks, quite rapid. DNA-DNA hybridisation sug­ passerines. They recognised two major assumed prominent positions. The rock­ One of the least well understood accipiters, eagles, Secretarybird and falcons) gests that buttonquails are the basal groups, one of which, the Corvida, jumpers of southern African and the groups has been the Old World warbler- Ciconiiformes (grebes, tropicbirds, gannets, cormorants, herons, group, followed by woodpeckers, bar­ comprises Australo-Papuan endemics, picathartes of West and Central Africa babbler complex. The warblers were Hamerkop, flamingos, ibises, pelicans, New World vultures, storks, frigatebirds, penguins, divers, petrels and albatrosses) bets and a slew of other ‘near-passerine’ plus several more widespread lineages. are sister groups, basal to all other pas­ traditionally placed in a single fam­ orders. Of the orders in Neoaves, only the Families found in Africa include crows, seridan birds. This suggests that Africa ily, Sylviidae. Sibley recognised the Passeriformes (perching birds) Galbuliformes (jacamars and puffbirds) shrikes, drongos, crested-flycatchers, played an important role in the early distinctiveness of the largely African 120 100 80 60 40 20 0 and Trochiliformes (hummingbirds) are orioles and cuckooshrikes, with bush- radiation of the Passerida. Cisticolidae (prinias, cisticolas, apalises, millions of years not represented in Africa, with one order, shrikes, batises and wattle-eyes endemic There is still lots to learn about the camaropteras, tailorbirds, etc), but fail-­ the Musophagiformes (turacos), being to the continent. All remaining species Passerida. Sibley’s view of three major ed to appreciate the full extent of the Relationships among bird orders, showing the approximate time that lineages diverged. confined to the continent. Despite their (some 35 per cent of all birds) were groups has been challenged, with several problem within the remaining warblers. Many of the relationships among Neoaves orders remain unresolved. diverse morphology, most waterbirds, placed in the Passerida, with three super- families falling outside the neat tripartite The predominantly Palearctic Sylvia 

68 bird systematics africa – birds & birding august/september 2005 bird systematics 69 The taxonomy of the Old World Warblers, such as this Lesser Swamp Warbler, remain in a state of flux. It is likely that they will be split into several new families.

concerted push to discover the ‘tree of life’, the history of the evolution of all life on earth. This requires sequencing a suite of conserved genes from literally thousands of organisms, including hun­ dreds of birds. Such initiatives will result in a stable family-level structure within peter ryan the next few years, but new surprises warblers are more closely related to bab­- and Australasian warblers that groups will doubtless emerge as more and more blers, white-eyes and laughing-thrushes with the Madagascan radiation of ‘bab­ genera are sequenced. than to other warblers. Preliminary blers’ and ‘bulbuls’. Some birders may consider these dis­ evidence suggests that the remaining Much work remains to be done, but the coveries irrelevant, and grumble about warblers also are deeply divided and rate of progress is astounding. Molecular changes to the old, familiar bird sequence. probably should be split into several techniques have improved to the point But you cannot understand an organism new families, including another largely where what once seemed impossible, and how it fits into its environment African group that would embrace such as sequencing the entire human without also knowing its evolutionary the crombecs, eremomelas, longbills, genome, is merely tedious. Earlier this history, and the constraints imposed by Grassbird, Rockrunner and Victorin’s year the entire genome for the chicken that history. Knowing the relationships Warbler. True Bradypterus warblers form was published with surprisingly little among the birds we watch can only part of a diverse array of African, Asian fanfare. Within systematics, there is a enhance our birding experience. 

New Zealand wrens (Acanthisittidae) Old World suboscines: pittas, broadbills, asities New World suboscines: ovenbirds, spinetails, ant-birds, woodcreepers, gnateaters, tapaculos, cotingas, manakins, tyrant-flycatchers and allies Menuroidea: lyrebirds and scrub-birds Ancient Australasian endemics: bowerbirds, whipbirds, honeyeaters, quail-thrushes, scrub-wrens and allies, including Australian ‘babblers’, ‘wrens’, ‘warblers’ etc. Corvoidea (core families): crows, true shrikes, vireos, drongos, fantails, birds-of-paradise, crested-flycatchers, paradise-flycatchers, Old World orioles, ioras, vangas, bush-shrikes, batises, wattle-eyes, cuckooshrikes, wood swallows and sundry Australasian endemics Picathartidae: rockfowl Chaetopidae: rock-jumpers Petroicidae: Australian robins Muscicapoidea: waxwings, flycatchers, chats, wheatears, thrushes, robins, dippers, starlings, mynas and mockingbirds Nuthatches, creepers, wrens, gnat-catchers (‘Certhioidea’) Tits, penduline tits, elminias and Fairy Flycatcher Sylvioidea: larks, nicators, Old World warblers, long-tailed tits, swallows, Erythrocercus ‘flycatchers’, bulbuls, babblers, laughing-thrushes, white-eyes Passeroidea: sugarbirds, leafbirds, sunbirds, flowerpeckers, weavers, widowbirds, finches, whydahs, sparrows, wagtails, pipits, accentors, canaries, honeycreepers, buntings, tanagers, and New World ‘warblers’, ‘orioles’ and ‘blackbirds’

Relationships within the Passeriformes, the largest order of birds.

70 bird systematics africa – birds & birding