Orioles: The Genuine Article

Eurasian golden oriole Oriolus oriolus, copyright Crusier.

It is widely appreciated that the British during the age of exploration were probably not the most imaginative of baptisers. Thanks to their tendency to label the fauna of foreign lands with the names of familiar animals back home, we are regularly confronted with warblers that aren't warblers, cod that aren't cod, monkeys that aren't monkeys. And for years, many an American has laboured under the mistaken impression that they know what an oriole is. This post is about the real orioles.

The Oriolidae are a family of birds found mostly in the tropics of the Old World, from Africa to Australia. Only a few species in the family are known from temperate climes. One of these is the original oriole, the European Oriolus oriolus, which migrates between sub-Saharan Africa and its breeding range in Europe and central Asia. The name 'oriole' is derived from the Latin word for 'golden', and there is no question of this being an appropriate name for the European bird. The male's plumage is almost entirely golden yellow, with the wings being black. As is commonly the way with birds, the females are less dramatic, being predominantly green. Despite the males' bright coloration, though, orioles are by all accounts fairly retiring birds, usually remaining secluded in the tree canopy, where they seek out fruit and small insects.

Black-and-crimson oriole Oriolus cruentus malayanus, copyright Christopher Hill.

The majority of the about thirty remaining species of Oriolus are also some combination of gold, green and/or black, but there are notable exceptions. A clade of Australo-Papuan and Moluccan species, identified by Jønsson et al. (2010) as the sister group to the other Oriolus species, contains relatively dull brown or greenish species. The Moluccan species in this clade bear a strong resemblance to friarbirds, a group of honeyeaters found in the same region, to the extent that the black-eared oriole Oriolus bouroensis was first described as a friarbird. It has been suggested that this represents a case of mimicry with the retiring orioles gaining a degree of protection from their resemblance to the aggressive friarbirds (Dickinson 2004). Another Asian clade identified by Jønsson et al. (2010) includes mostly red and black species. It also includes the silver oriole Oriolus mellianus in which the red coloration has been mostly lost, so that it is mostly silver-white with a black head and wings.

Male and female Australasian figbirds Sphecotheres vieilloti, copyright Jim Bendon.

Also included in the Oriolidae are the three species of figbird in the genus Sphecotheres, found in the Australo-Papuan region. The figbirds, as their name suggests, have a higher proportion of fruit in their diet than orioles. They are also more sociable, living in small flocks. Figbirds are distinguished from orioles by the presence of patches of bright red bare skin around their eyes; they are otherwise a dull greenish colour. Recent studies have also indicated oriolid affinities for Pitohui, a genus of two red and black birds, the hooded pitohui P. dichrous and variable pitohui P. kirhocephalus, found in New Guinea. Previous authors have included six species in Pitohui, but phylogenetic studies have revealed that the genus in the broad sense is widely polyphyletic, with the remaining species belonging to different bird families. The red and black markings of the 'pitohuis' are a case of aposematic coloration, advertising that its bearer is toxic. The pitohuis contain batrachotoxins in their skin and feathers, a similar substance to that found in the poison-arrow frogs of South America. Contrary to what you may read elsewhere, the pitohuis were not the first known case of toxicity in birds, though it was one of the most definite ones. It has been known since ancient times that migratory quail Coturnix coturnix are toxic at certain points on their migratory route: the biblical book of Numbers describes a case of mass poisoning suffered by the Israelites during the exodus. Other examples of birds that are at least seasonally toxic include the spur-winged goose Plectropterus gambensis and the bronzewing pigeons of the genus Phaps (a brief review of bird toxicity is provided by Bartram & Boland, 2001). As far as is known, all cases of toxicity in birds result from feeding on something containing the relevant toxic substance (probably beetles, in the case of pitohuis) which is then sequestered by the bird.

Mounted North Island piopio Turnagra tanagra, copyright Te Papa.

The Australo-Papuan distribution of these two genera, together with the basal position of the Australo-Papuan species in the genus Oriolus, suggests that the family originated in this area before crossing the Wallace Line to diversify in Eurasia and Africa (Jønsson et al. 2010). An Australo-Papuan origin for the orioles also correlates with the presence of a fossil oriolid, Longmornis robustirostrata, in the early Miocene Riversleigh deposit of Australia (Boles 1999). It also correlates with the recent identification as oriolids of the now extinct New Zealand piopios of the genus Turnagra (Zuccon & Ericson 2012). The piopios were two species (the South Island piopio Turnagra capensis and the North Island T. tanagra) of mostly brown songbirds, also commonly known as the New Zealand thrushes. Their song was described as being amongst the most beautiful of any New Zealand bird, both complex and with a propensity towards mimicking other birds. Though seemingly common at the time of European settlement, they declined rapidly and probably became extinct around the start of the 20th Century. The affinities of the piopios were long contentious, with leading suggestions including a relationship with the whistlers of the Pachycephalidae, or with the bowerbirds of the Ptilonorhynchidae. Zuccon & Ericson (2012) marshalled an array of molecular, morphological and behavioural evidence in favour of a relationship with the orioles, though this stands in contrast with an earlier molecular study that supported the bowerbird hypothesis (Zuccon & Ericson noted that the cytochrome b sequence reported in the earlier study did not correspond with the one they found themselves, and suggested that it may have been the result of contamination). The dull coloration of the piopios compared to other orioles was explained by Zuccon & Ericson as a loss of sexual dimorphism, but this may have been unnecessary: they seem to have overlooked the similarly dull coloration of a number of other basal oriolids. The fact that the piopios were described as more terrestrial than the other oriolids is also not unusual in the New Zealand context. After all, the New Zealand bird fauna is famed for its tendency towards terrestrialisation (it even included a terrestrial owlet-nightjar!) In an environment where the main threat came from above in the form of birds of prey, the ground must have seemed like a welcoming place to be.

REFERENCES

Bartram, S., & W. Boland. 2001. Chemistry and ecology of toxic birds. ChemBioChem 2: 809–811.

Boles, W. E. 1999. A new songbird (Aves: Passeriformes: Oriolidae) from the Miocene of Riversleigh, northwestern Queensland, Australia. Alcheringa 23: 51-56.

Dickinson, E. C. 2004. Systematic notes on Asian birds. 42. A preliminary review of the Oriolidae. Zool. Verh. Leiden 350: 47-63.

Jønsson, K. A., R. C. K. Bowie, R. G. Moyle, M. Irestedt, L. Christidis, J. A. Norman & J. Fjeldsa. 2010. Phylogeny and biogeography of Oriolidae (Aves: Passeriformes). Ecography 33: 232–241.

Zuccon, D., & P. G. P. Ericson. 2012. Molecular and morphological evidences place the extinct New Zealand endemic Turnagra capensis in the Oriolidae. Molecular Phylogenetics and Evolution 62: 414–426.

Whistling for Whistlers

Male and juvenile golden whistler Pachycephala pectoralis, photographed by S. Lloyd. Female golden whistlers resemble the juveniles.

The name Pachycephalidae (or some orthographic variant thereof such as Pachycephalinae) has long been used to refer to a group of small insectivorous birds from the Australo-Papuan region (summarised by Boles 1979 as 'large-headed stout-bodied birds with poorly developed rictal bristles'). In the past, taxa included in the Pachycephalidae included the New Zealand genera Mohoua and Turnagra, the crested shriketit Falcunculus frontatus and the crested bellbird Oreoica gutturalis. However, as has often been the case with the more generalised groups of passerine birds, recent authors have tended to whittle the family's contents down as molecular studies have scattered the constituent taxa about the family tree. In its most recent iterations, Pachycephalidae generally corresponds to the taxa included in clade 'CC5CC6b' of Jetz et al. (2012), comprising primarily the genera Pachycephala and Colluricincla, plus a small number of satellite taxa.

Bare-throated whistler Pachycephala nudigula, photographed by Lars Peterssen.

The genus Pachycephala is currently used for the whistlers, a group of about forty species of mostly long-tailed, stout-billed birds, often (but not always) with sexually dimorphic coloration, with a contrasting pectoral band (most often black in the males) dividing the throat from the chest. The exact number of species in the genus is somewhat uncertain due to disagreements about the status of several constituent populations: the golden whistler P. pectoralis complex, for instance, includes over 65 named taxa variously recognised as species or subspecies (Jønsson et al. 2010). Species of Pachycephala are found from southeast Asia through to Fiji and Tonga. Some of you may recall whistlers featuring in Dougal Dixon's Life after Man as giving rise to an island radiation including nut-cracking, wood-pecking and predatory species (my only question being, who was the Hart that the plesiomorphic species in the radiation is supposed to be named after?)

Grey shrike-thrush Colluricincla harmonica, photographed by Sammy Sam.

Colluricincla, the shrike-thrushes, includes at least four species found in Australia and New Guinea (excluding a couple of species better included in Pachycephala). They are larger, slenderer and more narrow-headed than the whistlers, with less dimorphic coloration. The grey shrike-thrush C. harmonica of Australia has a high reputation as a singer. Some recent authors have also suggested inclusion of two further New Guinean species, the rusty pitohui Pitohui ferrugineus and white-bellied pitohui P. incertus, in Colluricincla. The genus Pitohui has been used to include a group of about half a dozen New Guinean species in the Pachycephalidae, which are relatively large and brash as pachycephalids go. They are variously reddish, black, or some combination of the two (the white-bellied pitohui has, as its name indicates, a yellowish-white underside). They have become most notorious in recent years for the discovery that, with the apparent exception of P. incertus, they are in fact toxic, with their skin and feathers containing batrachotoxins comparable to those found in the arrow-poison frogs of South America. Like the arrow-poison frogs, the birds probably do not generate the toxin themselves, but accumulate it from a diet of toxin-carrying melyrid beetles. However, molecular studies have indicated that the genus Pitohui as previously recognised is polyphyletic. The hooded pitohui P. dichrous and the variable pitohui P. kirhocephalus, the latter of which is the type species of the genus, are more closely related to the Oriolidae than the Pachycephalidae, while three species remain close to Pachycephala and Colluricincla. As well as the two species mentioned previously (which may be included in Colluricincla or maintained as a distinct genus for which the name Pseudorectes is available), the black pitohui 'Pitohui' nigrescens should be included in the Pachycephalidae as its own genus Melanorectes. As well as being closer to black than the reddish Pseudorectes species, Melanorectes nigrescens apparently possesses a 'peculiar musky smell' (Rothschild & Hartert 1913).

Rusty pitohui Pseudorectes ferrugineus, photographed by Dubi Shapiro.

The remaining two species of the Pachycephalidae are placed by Jønsson et al. (2010) in the genus Coracornis: the maroon-backed whistler C. raveni of Sulawesi and the Sangihe shrike-thrush C. sanghirensis of Sangihe, north of Sulawesi (as the vernacular name suggests, this species was previously included in Colluricincla). Neither of these species appears to be particularly well-known: in particular, C. sanghirensis was first described in 1881 but not observed again for over 100 years until 1985 (Rozendaal & Lambert 1999). So long was the gap between observations that several authors had, in this time, assumed that the original specimen must have been mislabelled and come from somewhere in New Guinea rather than Sangihe. This misinterpretation was encouraged by the belief that the species was directly related to the little shrike-thrush Colluricincla megarhyncha, found on the wrong side of the Wallace line to easily colonise Sangihe. As it is, C. sanghirensis is restricted to only a small area of forest on Sangihe at an altitude above 600 m, and was regarded by Rozendaal & Lambert (1999) as critically endangered. Its identification with Coracornis rather than Colluricincla was done by Jønsson et al. (2010) on the basis of molecular analysis; when comparing C. sanghirensis with Colluricincla, Rozendaal & Lambert (1999) do not appear to have also considered Coracornis raveni.

Sangihe shrike-thrush Coracornis sanghirensis, photographed by Marc Thibault.

REFERENCES

Boles, W, E. 1979. The relationships of the Australo-Papuan flycatchers. Emu 79: 107-110.

Jetz, W., G. H. Thomas, J. B. Joy, K. Hartmann & A. O. Mooers. 2012. The global diversity of birds in space and time. Nature 491: 444-448.

Jønsson, K. A., R. C. K. Bowie, R. G. Moyle, L. Christidis, J. A. Norman, B. W. Benz & J. Fjeldså. 2010. Historical biogeography of an Indo-Pacific passerine bird family (Pachycephalidae): different colonization patterns in the Indonesian and Melanesian archipelagos. Journal of Biogeography 37: 245-257.

Rothschild, W., & E. Hartert. 1913. List of the collections of birds made by Albert S. Meek in the lower ranges of the Snow Mountains, on the Eilanden River, and on Mount Goliath during the years 1910 and 1911. Novitates Zoologicae 20 (3): 473-527.

Rozendaal, F. G., & F. R. Lambert. 1999. The taxonomic and conservation status of Pinarolestes sanghirensis Oustalet 1881. Forktail 15: 1-13.

The Shrikes of the South

Black-backed magpie (Gymnorhina tibicen), a member of the butcherbird family Cracticidae. Australian magpies are not closely related to the Eurasian true magpies (which are members of the crow family). They are best known for their vibrant warbling songs, and thinly veiled homicidal tendencies. Phot by Don Herbison-Evans.

Like them or loath them, there can be little argument that the introduction of molecular methods in the latter part of the last century revolutionised the study of phylogeny and evolution. In many cases, the results of molecular studies supported the theories already proposed about which taxa are related to which, and how. In other cases, molecular data came up with results that strongly contradicted what we thought we already knew. And in some cases, molecular studies gave results that had never been suggested before, but seemed perfectly reasonable in hindsight.


Black-headed gonolek (Laniarius erythrogaster), a member of the African bush-shrike family Malaconotidae. Photo by Derek Ramsey.

I have spoken elsewhere about the new picture of oscine (songbird) phylogeny which has arisen from molecular studies of the group. I'd recommend reading the second and third paragraphs of the post I've just linked to for the background to what I'm just about to talk about. Let it suffice to say that most of the Holarctic families of oscines belong to a clade called Passerida, which is nested within a series of mostly Australo-Papuan clades. Of these Australo-Papuan clades, the most diverse is the Corvoidea, which also includes a number of taxa that have dispersed outside of Oceania such as the crows and orioles (the proper Old World orioles, that is, not the American birds known as 'orioles' which are not orioles at all but members of the Passerida). Also included in the Corvoidea are the shrikes, Old World birds with hook-tipped bills that are more predatory than your average songbird.


White-breasted woodswallows (Artamus leucorynchus). Photo by Romy Ocon.

In 2004, Barker et al. published a phylogeny of the oscines that resolved a number of clades within the Corvoidea. Among the most interesting clades identified by this study was one that united the bush shrikes (Malaconotidae) and helmet-shrikes (Prionopidae) of Africa (both previously counted as subfamilies of the Laniidae) with the woodswallows (Artamus) and butcherbirds (Cracticidae) of Australia. This was definitely one of the third class of molecular results that was unexpected but sensible, as the cracticids are in many ways the shrikes of Australia. The new clade, which lacks a name but which for convenience I'll dub the 'malaconotoid clade', therefore combines many of the world's shrike-like birds in one convenient package. The notable exceptions are the true Eurasian shrikes of the stripped-down family Laniidae, which are Corvoidea but whose affinities seem to lie elsewhere as the sister group of the crows, and the Asian shrike-babblers of the genus Pteruthius, which Reddy and Cracraft (2007) showed to be corvoids related to the American vireos.


Bornean bristlehead (Pityriasis gymnocephala). Authors had disagreed continuously over the years about whether Pityriasis was related to the shrikes or the cracticids - a somewhat ironic argument since the recognition of the malaconotoid clade. Photo by James Eaton - photos of this retiring bird are few and far between, making this all the more impressive.

Comparison with the other corvoids suggests that the malaconotoids had an Australian origin, a suggestion corroborated by the fact that the basalmost split in the group seems to be between the Australian taxa on one side and the African taxa on the other (Barker et al., 2004; Moyle et al., 2006). As with all good scientific theories, this brings up a further question - how did the malaconotoids get from Australia to Africa? To answer this question, it turns out that a collection of small southern Asian families also fall into the malaconotoid clade - the Platysteiridae, the ioras of the genus Aegithina, and the unusual Bornean bristlehead (Pityriasis gymnocephala). The reasonable suggestion might therefore be made that southern Asia was used as a corridor by the malaconotoids on their way to Africa. Unfortunately, the evidence is a little more equivocal in this regard. It is true that the Asian taxa sit on the African side of the malaconotoid clade (Moyle et al., 2006 - Fuchs et al., 2006, found Aegithina to be sister to the Australian taxa, but with low support), but there is no clear division between taxa from the two continents. Instead, the African and Asian taxa are mixed together, suggesting more than one dispersal between the continents and also unclear whether dispersal was from Asia to Africa or vice versa.



The other significant dispersal in the history of the malaconotoids was from Africa to Madagascar, where an ancestral malaconotoid gave rise to the vangas (Vangidae). The vangas were one of the very few oscine groups to reach Madagascar, and once there they formed an island radiation comparable to the honeycreepers of Hawaii or the finches of the Galapagos. While there are only twenty-one species of vanga, the group is spectacularly diverse ecologically, as shown above in a figure from Yamagishi et al. (2001) - so much so, in fact, that many of the species had been assigned to separate families and were only recognised as vangas recently (see Don Roberson's page on the family for further details). Notable in this regard are the handsome sickle-billed vanga (Falculea palliata), the coral-billed nuthatch (Hypositta corallirostris) which bears an uncanny resemblance to the unrelated true nuthatches, and the large-billed helmetbird (Euryceros prevostii).

REFERENCES

Barker, F. K., A. Cibois, P. Schikler, J. Feinstein & J. Cracraft. 2004. Phylogeny and diversification of the largest avian radiation. Proceedings of the National Academy of Sciences of the USA 101: 11040-11045.

Fuchs, J., J. Fjeldså & E. Pasquet. 2006. An ancient African radiation of corvoid birds (Aves: Passeriformes) detected by mitochondrial and nuclear sequence data. Zoologica Scripta 35 (4): 375-385.

Moyle, R. G., J. Cracraft, M. Lakim, J. Nais & F. H. Sheldon. 2006. Reconsideration of the phylogenetic relationships of the enigmatic Bornean bristlehead (Pityriasis gymnocephala). Molecular Phylogenetics and Evolution 39 (3): 893-898.

Reddy, S., & J. Cracraft. 2007. Old World shrike-babblers (Pteruthius) belong with New World vireos (Vireonidae). Molecular Phylogenetics and Evolution 44 (3): 1352-1357.

Yamagishi, S., M. Honda, K. Eguchi & R. Thorstrom. 2001. Extreme endemic radiation of the Malagasy vangas (Aves: Passeriformes). Journal of Molecular Evolution 53: 39-46.

On Hybrid Birds

Fuller, E. 1995. The Lost Birds of Paradise. Swan-Hill Press.

The 19 "lost" birds of paradise that Errol Fuller describes in this book are forms that are mostly only known from very few specimens, often with very little supporting information. What makes them "lost", however, is that despite all but one of them being described as new species, all of them were later reinterpreted as hybrids between better-known species. Fuller's motivating question is whether these specimens are indeed hybrids, or represent valid species that might occupy unknown restricted ranges somewhere in the depths of New Guinea, or may perhaps have slipped into extinction without ever getting the recognition they deserved.

Most of the specimens reached Europe through the plume trade. Specimens of birds of paradise were purchased from native collecters and then shipped back to the West for use in the fashion industry (the first country to ban the import of birds of paradise for plumes, according to Fuller, was the US in 1913, a development that probably had less to do with the developing conservation movement than with the increasing unfashionability of wearing plumes*). As a result, the available collection data on most specimens is decidedly hazy - few bear more specific information than "Dutch New Guinea" (the western part of New Guinea that is now controlled by Indonesia). Even if a more specific locality is recorded, it is often unreliable - specimens could be passed through a number of different native tribes before eventually reaching the European traders. Throughout the book, we get introduced to many of the figures involved in the collection and study of these mystery birds.

*To add further complexity, a major factor in the decline of popularity of plumes was actually the rise in popularity of the motor-car - ornate plumed hats being decidedly impractical for wearing in open-topped cars.

'Paradisaea mirabilis', a possible hybrid of Paradisaea minor (lesser bird of paradise) and Seleucidis melanoleuca (twelve-wired bird of paradise). 1902 lithograph by Bruno Geisler.

Throughout Fuller's book, we get introduced to many of the personages involved in the collection and study of the specimens (including the spectacularly named Captain Neptune Blood*). A significant number passed through the collection of Lord Walter Rothschild, a somewhat eccentric enthusiast who amassed one of the world's largest private natural history collections (Darren Naish wrote a piece two years ago on Rothschild and his unusual enthusiasm for cassowaries), though many of Rothschild's bird of paradise specimens were included in the collection he was blackmailed into selling to the American Museum of Natural History**. The "hybrid" specimens were largely identified as such in 1930 by Erwin Stresemann. Fuller accuses Stresemann of overzealousness in embracing his hybrid theory of origin for "species" known only from one or two specimens, essentially assuming from the start that all such species must be hybrids of known species and identifying "parents" from the available options no matter how poorly supported.

*Seriously.

**Probably not, I hasten to add, by the American Museum of Natural History.

'Diphyllodes gulielmitertii', almost certainly a hybrid between Diphyllodes magnificus and Cicinnurus regius. Unlike most of the other forms described by Fuller, this hybrid occurs fairly commonly, with more than two dozen known specimens. Lithograph by J. Gould and W. Hart.

Unfortunately, many of Fuller's reinterpretations of the supposed hybrids end up falling a little flat. Fuller accepts a hybrid origin for some forms, refutes it for others, but in many cases it is debatable whether his interpretations are any better than Stresemann's. Because all Fuller has to go on is examination of specimens, most of his arguments for valid species status amount to little more than replying to Stresemann's statement that "Species A has features intermediate between those of B and C, and is therefore a hybrid between the two" with "No it doesn't, so it isn't". In two cases where Fuller does accept hybrid status, 'Loborhamphus ptilorhis' and 'Lamprothorax wilhelminae', the reasons for linking them to their supposed parents seem decidedly unconvincing (which, of course, does not eliminate the possibility that they could still be hybrids between other species), while 'Cicinnurus lyogyrus', which Fuller hesitatingly accepts as a hybrid of the king bird of paradise (Cicinnurus regius) and the magnificent bird of paradise (Diphyllodes magnificus) seems more likely to be simply an aberrant variant of Cicinnurus regius. In contrast, 'Janthothorax bensbachi', which Fuller suggests is a valid species, seems more likely to be a hybrid. Probably DNA analysis of the specimens would be the only way to convincingly decide the question one way or another - Fuller suggests this would be difficult because the close relationships of the parent species would make results unconvincing, but resolution of molecular analyses has decidedly improved since 1995. The main barrier would be that DNA extraction from museum specimens, especially ones that have been in storage since the 1800s (and were probably not exactly fresh when they first reached the museum) is a difficult process, with little guarantee of success.

Loborhamphus nobilis, regarded by Stresemann (1930) as a hybrid between Paradigalla carunculata and Lophorina superba, but by Fuller as a probable valid species. Unlike the other bird of paradise species mentioned in this post, the less sexually dimorphic Paradigalla species are not polygamous breeders, and form permanent pair bonds. They therefore strike me as less likely to produce hybrids.

The Lost Birds of Paradise is certainly a lavishly illustrated book, reproducing paintings by Gould and other spectacular bird illustrators (some of which I've taken the liberty of re-reproducing), as well as numerous photos and drawings. The distribution and subjects of these illustrations are often a little erratic, however - what's with the naked man in the bath on page 76? - and this same erraticism extends to the text. I can't escape the impression that most of the essays on the various birds were composed separately, with little cross-checking between chapters when the book was compilated. The story of Stresemann's 'overzealous' revisions is repeated a number of times in different chapters, for instance, while many chapters include rather tangential passages on matters related to birds of paradise in general, but not necessarily directly relevant to the specific form the chapter is devoted to (not surprisingly, this is particularly noticeable in some forms known only from single specimens for which otherwise Fuller probably just wouldn't have had that much to say). Probably this eclecticism is most marked in the chapter on 'Paradisaea mixta', in which we are treated to a lengthy quotation from the autobiography of Errol Flynn (complete with full-page photograph) and a description of his experiences trying to start a career collecting birds of paradise in New Guinea some years before he became an actor. And what does this have specifically to do with 'Paradisaea mixta'? As it happens, absolutely nothing.

Still, The Lost Birds of Paradise is easily readable, and at least highlights that the identity of many of the "hybrid" birds of paradise is not as firm as might be thought. A commentor on one discussion thread makes the comment that Fuller obviously really wants there to be overlooked species of birds of paradise, which may lead him to be a bit more hasty in his judgements than he probably should be. Nevertheless, New Guinea, especially the western half, is a surprisingly unexplored place, and as the recent discovery/rediscovery of unknown or near-unknown mammal species there shows, it would be wise to not rule anything out just yet.

Yet another passerine 'family'

I discovered yesterday via Creagrus that the stitchbird (Notiomystis cincta) has been elevated to 'new monotypic family' status in a recent paper in the Australian Journal of Zoology (Driskell et al., 2007). This has been in the works a little while - a preliminary paper a year ago reported on its unexpected position (Ewen et al., 2006). Stitchbirds are a highly vulnerable species of passerine from the North Island of New Zealand - I say 'vulnerable' rather than 'endangered' because I believe populations are fairly healthy in the very few areas they are found, but they could easily fall victim if those areas were invaded by introduced predators - the only surviving natural population is on Little Barrier Island, but they have been re-introduced on Tiritiri Matangi Island and the Karori Wildlife Sanctuary in Wellington. I was fortunate enough to see both males and females at Karori last year while I was unsuccessfully trying to find harvestmen. The male is a quite attractive little bird with a black head with white streaks on the cheeks (the image here is by Michael Szabo, and comes via GrrlScientist. In the past, the stitchbird has been included in the family Meliphagidae (honeyeaters - superfamily Meliphagoidea), but the genetic data analysed by the two papers shows that it is actually sister-group to the endemic New Zealand family Callaeidae (wattlebirds - superfamily Corvoidea)*. The Callaeidae + Notiomystis clade makes for a nice little endemic New Zealand radiation - though only four genera and a maximum of six species** are known, all genera are quite distinct from each other.

*The wattlebirds are referred to as Callaeidae or Callaeatidae, and I must confess I haven't a clue which is correct. The type genus is Callaeas.

**I say "maximum of six" because authors differ whether the two taxa each in Callaeas (kokakos) and Philesturnus (saddlebacks) are species or subspecies - current opinion favours the former.

A little background here so you know what I'm talking about - the Passeriformes are the perching birds, and are the largest of the generally recognised bird orders. Traditionally, Passeriformes have been divided between Oscines (songbirds) and suboscines - it's the Oscines that concern us at the moment. In the past, Oscines were divided into a large number of families, but most were relatively small with the vast majority of species included in a few giant cosmopolitan families such as Muscicapidae (flycatchers) and Sylviidae (warblers). While it was long realised that this situation wasn't entirely satisfactory, it more or less persisted until the appearance of the DNA-DNA hybridisation studies of Sibley & Ahlquist (Sibley & Ahlquist, 1990) completely overturned the boat.

Sibley & Ahlquist identified a major split in the Oscines into two clades. The shocking part was that these clades were almost totally unexpected - rather than lining up with the previously recognised families, Sibley and Ahlquist recognised a division between mostly Australasian oscines (Corvida) and the mostly Holarctic Passerida. Genera that were once regarded as fairly closely related were placed on opposite sides of the divide, with massive morphological convergences implicated. Further testing has refined the idea slightly (Ericson et al., 2002; Barker et al., 2004), such that while the Passerida has remained monophyletic, the 'Corvida' are now regarded as paraphyletic with regard to the Passerida. As things currently stand, the Menurae (lyrebirds and scrub-birds) are the basalmost Oscines (as originally predicted by morphology), followed by a small clade of Climacteridae (Australian woodcreepers) + Ptilonorhynchidae (bowerbirds), then the Meliphagoidea (honeyeaters and fairy wrens), then the Passerida (most Holarctic songbirds) sister to the Corvoidea (mostly Australasian songbirds, as well as a number of non-Australasian taxa such as crows and shrikes). The upshot of all this is that to move the stitchbird from Meliphagoidea to Corvoidea is a fairly significant shift.

I do have one quibble with this paper, though, which effectively amounts to a quibble about the current state of passerine taxonomy as a whole. As more and more taxa are shifted about on the passerine tree, the general response has been to divide them into smaller and smaller families. Yes, the idea of a "family" rank doesn't really mean anything, and ultimately the recognition of such is entirely arbitrary, but there are still pragmatic implications to what gets recognised as a "family" and what doesn't, because this is a rank often used in assessing diversity. Why should Notiomystis get its own "family"? Recognising a monotypic family tells us nothing about its relationships. In my opinion, it would have been far more informative to expand the concept of Callaeidae and place Notiomystis as its basalmost member. But as I already said, the recognition of family rank is entirely arbitrary, and there is ultimately no obligation to accept my option over the authors'.

REFERENCES

Barker, F.K., A. Cibois, P. Schikler, J. Feinstein, and J. Cracraft. 2004. Phylogeny and diversification of the largest avian radiation. Proceedings of the National Academy of Sciences of the USA 101: 11040-11045.

Driskell, A., L. Christidis, B. J. Gill, W. E. Boles, F. K. Barker & N. W. Longmore. 2007. A new endemic family of New Zealand passerine birds: adding heat to a biodiversity hotspot. Australian Journal of Zoology 55: 73-78.

Ericson, P. G. P., L. Christidis, M. Irestedt & J. A. Norman. 2002. Systematic affinities of the lyrebirds (Passeriformes: Menura), with a novel classification of the major groups of passerine birds. Molecular Phylogenetics and Evolution 25: 53-62.

Ewen, J. G., I. Flux & P. G. P. Ericson. 2006. Systematic affinities of two enigmatic New Zealand passerines of high conservation priority, the hihi or stitchbird Notiomystis cincta and the kokako Callaeas cinerea. Molecular Phylogenetics and Evolution 40 (1): 281-284.

Sibley, C. G., & J. E. Ahlquist. 1990. Phylogeny and Classification of Birds: a Study of Molecular Evolution. Yale Univ. Press: New Haven (CT).