Stilts and Avocets

Visit a healthy wetland in many parts of the world and you may be able to see boldly patterned, lightly built birds with remarkably long legs and bills wading through the shallows. These are the members of the Recurvirostridae, commonly known as the stilts and avocets.

American avocets Recurvirostra americana, from here.

About a dozen species of recurvirostrid are currently recognised, depending on the exact classification scheme in play. They are divided between three genera with the avocets forming the genus Recurvirostra and the stilts divided between Himantopus and Cladorhynchus. The most obvious distinction between the two subgroups is in the shape of the bill: that of stilts is straight but avocets have a distinct upwards curve towards the end of theirs. A fourth genus has often been included in the Recurvirostridae for the ibisbill Ibidorhyncha struthersii, a striking-looking inhabitant of the upland rivers of the Himalayan plateau, but uncertainty about this bird's phylogenetic position has led most recent authors to exclude it from the family.

The recurvirostrids feed mostly on small aquatic invertebrates such as brine shrimp or insect larvae. Their long legs, among the longest relative to body size of any bird, allow them to wade in deeply in search of prey. Stilts actively probe the waters and underlying sediment whereas avocets tend to forage by sweeping their bill through the water side to side. Avocets and the banded stilt Cladorhynchus leucocephalus of Australia prefer brackish waters such as lagoons and estuaries, with the banded stilt congegrating around the great salt lakes of inland Australia. Breeding is conducted by monogamous pairs that share the duty of incubating their simple nest on the ground near water. These nests may be gathered into loose colonies; the banded stilt forms particularly large colonies in which the chicks are herded into communal creches of several hundred.

Pied stilt Himantopus leucocephalus, copyright JJ Harrison.

The majority of recurvirostrids are patterned with black or dark brown and white. The red-necked avocet Recurvirostra novaehollandiae has the head and neck coloured reddish-brown as does the American avocet R. americana during the breeding season. The banded stilt has a broad reddish-brown band across the top of the breast. There is also the black stilt Himantopus novaezelandiae of New Zealand, which is somewhat self-explanatory. Beaks are black in all species; the legs are grey in avocets and red in stilts.

Four geographically distinct species of avocet occupy the modern world: the American avocet in North America, the red-necked avocet in Australia, the pied avocet Recurvirostra avosetta in Eurasia and Africa, and the Andean avocet R. andina in South America. The Andean avocet is a bird of high altitudes, occupying shallow, alkaline lakes in the upper Andes. Cladorhynchus includes only the banded stilt. The most varied taxonomy concerns the genus Himantopus. Historically, all the black-and-white stilts (and sometimes also the black stilt) have been recognised as a single near-cosmopolitan species. In more recent years, the trend has been towards recognition of five or six distinct species in the genus. Most of these species are well separated geographically except for in New Zealand where the black stilt shares its range with the pied stilt Himantopus leucocephalus, a more recent immigrant from Australia. The breeding range of the black stilt is currently restricted to a relatively small area of New Zealand's South Island, and the species is considered endangered due to factors such as habitat alteration and the threat of hybridisation with the more abundant pied stilt*.

*It's worth spending some thought on the role of hybridisation as a conservation risk. Some observers may express concern that regarding hybridisation as a threat per se carries uncomfortable intonations of "racial purity", and that limiting the available gene pool may do more harm than good. After all, it's not as if the black stilt heritage of hybrid individuals is just gone (hybrids between the two species are, I believe, fully fertile and able to produce offspring of their own). The question is, I suppose, do the black stilt genes actually persist in the mixed population? Or does selection and/or drift winnow them out over time? This would be a difficult question to answer, and not without risk to find out.

Banded stilts Cladorhynchus leucocephalus and red-necked avocets Recurvirostra novaehollandiae, copyright Ed Dunens.

Phylogenetically, it is reasonably well established that recurvirostrids form a clade with the ibisbill and oystercatchers. This clade is in turn closely related to the plovers of the Charadriidae; indeed, many recent phylogenies have indicated that the recurvirostrid-oystercatcher clade may even be nested within the plovers as generally recognised. Considering the relatively small number of species in each clade, it might seem reasonable to suggest the recurvirostrids be reduced to a subfamily of the Charadriidae, but bird taxonomists being bird taxonomists, there seems to be more of a push to divide the Charadriidae up instead.

The fossil record of the Recurvirostridae is limited. A handful of species have been assigned to this family from the Eocene, but all are known from limited remains and their position is questionable. Coltonia recurvirostra is known from part of a wing from Utah; it was a relatively large bird, appearing to be more than one-and-a-half times the size of any living recurvirostrid. Fluviatilavis antunesi was described from a femur, humerus and radius from Portugal but was described as exhibiting some primitive features not found in modern recurvirostrids. It is also worth noting that its original description (Harrison 1983) compared it most favourably with the ibisbill, so if that species is not to be regarded as a recurvirostrid, probably neither is Fluviatilavis.

REFERENCE

Harrison, C. J. O. 1983. A new wader, Recurvirostridae (Charadriiformes), from the early Eocene of Portugal. Ciências da Terra 7: 9–16.

The Psitteuteles Lorikeets

Varied lorikeet Psitteuteles versicolor, copyright Joshua Robertson.

Few groups of birds have been the object of human interest as much as parrots, with their striking coloration and intelligence inviting comment at least as far back as ancient Greek times. This interest has continued into recent times and scientific research into all aspects of parrot life has been extensive. Nevertheless, the classification of parrots has long been problematic. As a group, parrots combine a high degree of superficial disparity in features such as colour pattern with an underlying overall morphological conservatism (a not uncommon issue with birds). As such, though recognition of distinct species may be fairly straightforward, establishing the relationships between those species may be less so. Prior to the advent of molecular studies, few higher groups of parrots could be considered widely accepted. One such group was the lories, found in Australasia and the Pacific Islands (smaller members of this group are known as 'lorikeets' but, as with 'parrots' vs 'parakeets', the difference between the two is a question of size and shape rather than affinities). Members of this group evolved a long, narrow, brush-tipped tongue that allowed them to pursue a diet of nectar and pollen (Schweizer et al. 2015). About a dozen genera of lories are currently recognised: one such genus, Psitteuteles, is the subject of the current post.

Goldie's lorikeets Psitteuteles goldiei, copyright Ltshears.

Psitteuteles is commonly recognised to include three species of smaller lory: the varied lorikeet P. versicolor, the iris lorikeet P. iris and Goldie's lorikeet P. goldiei. In general, these are primarily green species with a red forehead and with varying amounts of blue across the back of the head and/or behind the eyes. The plumage is longitudinally streaked in the varied lorikeet and Goldie's lorikeet. Goldie's lorikeet has mauve cheeks whereas those of the varied lorikeet are partially yellow. The varied lorikeet is also mauve across the upper breast whereas the other two species are more evenly green. All three species are separated geographically: the varied lorikeet is widespread in northern Australia, Goldie's lorikeet is found in New Guinea and the iris lorikeet is found on the islands of Timor and Wetar in Indonesia. The varied lorikeet is particularly common in association with paperbarks and eucalypts around streams and waterholes, migrating as required to find trees in flower. Similar wandering habits are characteristic of Goldie's lorikeet which is mostly found in montane forest. The more sedentary iris lorikeet is mostly found in lowland monsoon forest. The varied and Goldie's lorikeets are not currently regarded as being of conservation concern but the iris lorikeet is more threatened by habitat loss and collection for the pet trade.

Iris lorikeet Psitteuteles iris, copyright Dick Daniels.

Not all authors have recognised Psitteuteles as a distinct group: some have included its species in the related genus Trichoglossus with the rainbow and scaly-breasted lorikeets. Recent phylogenetic studies suggest that suspicion of Psitteuteles' status may not be unwarranted. Molecular studies by Schweizer et al. (2015) and Provost et al. (2018) both fail to identify the three Psitteuteles species as forming a single clade. Instead, P. iris is placed close to Trichoglossus species whereas P. versicolor and P. goldiei are both placed outside a clade including Trichoglossus and related genera such as Eos, the red lories, and the musk lorikeet Glossopsitta concinna. A case could probably be made for restricting Psitteuteles to the varied lorikeet as type species while including the iris lorikeet in Trichoglossus. The fate of P. goldiei is more uncertain: though neither of the aforementioned studies identified P. versicolor and P. goldiei as sister species, it might be too early to exclude the possibility. Alternatively, should P. goldiei prove too phylogenetically isolated to include in any pre-existing genus, I am not aware of any available genus name for it. As seems to be one of my standard sign-offs on this site, further study is required.

REFERENCES

Provost, K. L., L. Joseph & B. T. Smith. 2018. Resolving a phylogenetic hypothesis for parrots: implications from systematics to conservation. Emu 118 (1): 7–21.

Schweizer, M., T. F. Wright, J. V. Peñalba, E. E. Schirtzinger & L. Joseph. 2015. Molecular phylogenetics suggests a New Guinean origin and frequent episodes of founder-event speciation in the nectarivorous lories and lorikeets (Aves: Psittaciformes). Molecular Phylogenetics and Evolution 90: 34–48.

The Wingless Penguin

A couple of weeks ago, I put up a page on the 'terrestrial penguin' Cladornis pachypus, described from the Oligocene of Patagonia by the Argentine palaeontologist Florentino Ameghino. As it happens, Cladornis wasn't the only unusual penguin recognised from the Patagonian fossil record by Ameghino nor was it even necessarily the most unusual. That title should probably go to another species, the wingless Palaeoapterodytes ictus.

Anterior (left) and posterior view of humerus of Palaeoapterodytes ictus, from Acosta Hospitaleche (2010). Scale bar = 10 mm.

Like Cladornis, Palaeoapterodytes was based on only a single bone, in this case a humerus (upper wing bone) from the Early Miocene. And also like Cladornis, Ameghino's description of this bone indicated a truly remarkable bird. The distal part of the humerus lacked any sign of the facets that would normally articulate with the succeeding wing bones and, as a result, Ameghino concluded that the wing skeleton had been reduced to the humerus only. The crest and pits on the humerus marking the attachment of the wing muscles were also reduced. Ameghino's Palaeoapterodytes presumably had wings reduced to the merest nubs, effectively functionless and probably of little mobility. Nevertheless, the humerus of Palaeoapterodytes remained relatively robust, its breadth little less than that of other penguins.

I am not aware of any other bird with a wing structure anything like this. In other birds without functional wings, the entire wing skeleton becomes reduced, not simply truncated. Perhaps the closest approximation I have found is the wing of Hesperornis, which also lacks known wing bones beyond the humerus. However, the Hesperornis humerus is slender and gracile, and even without direct indication of the presence of more distal bones, it still looks to retain some remnant of the ancestral articulation. Also, the whole concept of a wingless penguin is decidedly problematic. Hesperornis derived its main propulsion in swimming from its feet and so its wings became reduced because they served little function. Penguins, on the other hand, get most of their propulsion from their wings, swimming in a manner that has been compared to flying underwater. Despite being flightless, penguins retain a wing skeleton that is, if anything, even more well developed than that of their flying relatives. For Palaeoapterodytes to have lost functional wings, it would have somehow had to change its mode of propulsion.

Reconstruction of the Palaeoapterodytes humerus with missing sections restored, from Acosta Hospitaleche (2010).

As a result, even while authors were cautiously considering Ameghino's interpretation of Cladornis, they treated Palaeoapterodytes with more scepticism. This scepticism was eventually concerned when the humerus was re-examined by Acosta Hospitaleche (2010). The reason for the lack of structure at its distal end was very simple: the original distal end had been broken off. The apparent lack of development of the muscle attachment structures was the result of erosion, not any indication of the bone's original appearance. When alive, Palaeoapterodytes had probably been very similar to, if not identical with, one of the several other penguin species known from around the same time and place. Unfortunately, the state of preservation of the type humerus is so poor that its exact identity cannot be determined, and Palaeoapterodytes ictus has been cast into the taxonomic limbo of nomen dubium. Ameghino's Cladornis may remain an intriguing mystery, but his Palaeoapterodytes is just a red herring.

REFERENCES

Acosta Hospitaleche, C. 2010. Taxonomic status of Apterodytes ictus Ameghino, 1901 (Aves; Sphenisciformes) from the Early Miocene of Patagonia, Argentina. Neues Jahrbuch für Geologie und Paläontologie—Abhandlungen 255 (3): 371–375.

The Patagonian Land Penguin

Take a good look at the figure above, which comes from Mayr (2009). It shows the fossilised tarsometatarsus (the fused long bone of the foot) of a bird from the late Oligocene of Patagonia. This may be one of the single most mysterious specimens in the fossil record. It represents all we know to date of Cladornis pachypus, described by Argentinean palaeontologist Florentino Ameghino in 1895. The appearance of the bone, being very broad and flat relative to its length, is quite bizarre and does not much resemble the tarsometatarsus of any other known bird.

The first thing that should be pointed out is that, whatever it was, Cladornis was a large bird. The specimen is not completely preserved (part of the proximal end of the bone has been lost) but its overall shape suggests that its original length was probably not too much longer than what we have. As such, the tarsometatarsus was probably comparable in length to that of a large pelican. However, it was much wider relative to length than that of a pelican, suggesting the possibility of a more robust bird. The shape of the bone's end indicates that the toes would have been widely spaced, and it may have even approached a zygodactyl arrangement (with two toes pointed rearwards and two forwards, like a modern parrot*) (Mayr 2009).

*When explaining this to my partner, I suggested that he imagine a parrot the size of a pelican. He shuddered and declared that he would rather not.

When Ameghino (1895) first described Cladornis, he interpreted it as an aquatic bird and suggested a relationship to the penguins, albeit in an extinct family Cladornidae (later authors would correct this to Cladornithidae). Later, noticing that it was preserved in association with terrestrial mammals, he declared that it was not marine and was possibly even terrestrial (he also included another species from the same formation, Cruschedula revola, in the Cladornithidae; this species is based on part of a scapula and there is no telling if it was related to Cladornis or not). He still maintained its relationship to the penguins (Ameghino 1906). Ameghino had a bit of a thing for trying to find the origins of all major modern vertebrate groups in his native South America (one of his other works was a book arguing for an Argentinean origin of humans) and it is possible that this was in play here. Nevertheless, the idea of a 'Patagonian land penguin' held sway until Simpson's (1946) review of the fossil penguins, in which he declared that Cladornis was "so very unlike any other penguin, recent or fossil, that I can only consider its reference to that group as erroneous".

This left Cladornis' taxonomic position completely up in the air (the question of whether Cladornis itself could get up in the air is, of course, currently completely unswerable). Wetmore (1951) included Cladornis in the Pelecaniformes, because...reasons. The closest he gave to an explanation was, "The only suggestion that has come to me is that possibly they may belong in the order Pelecaniformes, in which I have placed the family tentatively in the suborder Odontopteryges, where it is located with two others of almost equally uncertain status. This allocation is wholly tentative and is no indication of belief in close relationship in the three diverse groups there assembled". He would later move Cladornis into its own suborder, Cladornithes, and no close relationship to the 'Odontopteryges' (now the Pelagornithidae) has been suggested since. Our current understanding of bird phylogeny finds Wetmore's remaining 'Pelecaniformes' to correspond to three or four independent clades (the Pelecanidae, Suliformes, Phaethontidae and probably Pelagornithidae) so his assignment of Cladornis to this group becomes almost completely uninformative.

Which is pretty much where we're forced to leave things. Mayr (2009) included Cladornis in his chapter on 'land birds', with other taxa discussed in this chapter belonging to the clade Telluraves. However, this was motivated more by a lack of any idea what to do with it otherwise than anything else (it is possible that Cladornis' sub-zygodactyly played a role, but not all zygodactylous birds belong to the Telluraves). I did notice a similarity in proportions between the Cladornis tarsometatarsus and the corresponding bone in the large phorusrhacid Brontornis, making me wonder if anyone had ever compared the two, but this may well be only superficial. Most recent authors have assumed that the Cladornis tarsometatarsus is simply too weird, too unique, for any resolution of its affinities to be reached without first finding more complete remains of the animal.

REFERENCES

Ameghino, F. 1895. Sur les oiseaux fossiles de Patagonie et la aune mammalogique des couches a Pyrotherium. Boletín del Instituto Geográfico Argentino 15 (11–12): 501–602.

Ameghino, F. 1906. Enumeración de los Impennes fósiles de Patagonia y de la Isla Seymour. Anales del Museo Nacional de Buenos Aires, serie 3, 6: 97–167.

Mayr, G. 2009. Paleogene Fossil Birds. Springer.

Simpson, G. G. 1946. Fossil penguins. Bulletin of the American Museum of Natural History 87 (1): 1–99.

Wetmore, A. 1951. A revised classification for the birds of the world. Smithsonian Miscellaneous Collections 117 (4): 1–22.

The Ostrich: From Whence this Derpy Horror?

Male and two female ostriches Struthio camelus, copyright Yathin S. Krishnappa.

Ostriches are widely known for two things: firstly, that they are the largest living bird by a quite respectable margin, and secondly, that they look ridiculous. Seriously, is there anyone out there who can look at the animals in the picture above and not think them ludicrous. Though I am, admittedly, invoking the luxury of distance: my uncle spent a year or two raising ostriches back during the brief boom of ostrich farming in New Zealand in the early 2000s, and I can say from experience that what looks humorous from afar is, close up, intimidating in a way no other animal is. They're just so tall*.

*Not to mention their well-earned reputation for gobbling down any item that attracts their attention. There are numerous stories out there demonstrating that wearing jewellery in an ostrich enclosure is a bad idea.

The modern ostrich is commonly regarded as a single species, Struthio camelus, found in savannah and semi-desert habits around Africa. There are some grounds for recognising the Somali ostrich S. molybdophanes of the Horn of Africa as a separate species—it is both genetically and morphologically divergent from other ostrich populations (for instance, its skin is blue rather than pink or red), and there is a small amount of overlap in range between Somali and typical ostriches—but this question remains open. Other subspecies are the North African ostrich S. c. camelus, the southern ostrich S. c. australis, and the Masai ostrich S. c. massaicus of Tanzania and Kenya. A fifth subspecies, the Arabian ostrich S. c. syriacus, became extinct around 1940, though it is worth noting that mitochondrial DNA extracted from specimens of Arabian ostriches in the British Museum did not separate them from the North African ostrich (Robinson & Matthee 1999). Ostriches can not really be confused with any other modern bird: not only is their remarkable size (matched by the remarkable size of their eggs), but they are the only birds to have reduced the number of toes to just two, with only the third and fourth toes of the standard bird foot remaining. This feature is generally presumed to be related to their cursorial lifestyle.

More evidence that ostriches are just daft. Copyright Georges Olioso.

Ostriches are members of the group of birds known as palaeognaths, that also includes such birds as the emu, kiwis, cassowaries, rheas and tinamous (the flightless members of the palaeognaths are commonly referred to as the ratites, but recent studies have cast doubt on whether flightlessness in the palaeognaths has a single origin). Phylogenetic relationships within the palaeognaths have been shuffled about considerably over the years (and even now are probably not really settled), but it is generally agreed that ostriches probably diverged from their nearest living relatives a long time ago (Burleigh et al. [2015], for instance, place them as the sister taxon to all other palaeognaths). Just how long ago we can't really say, the early fossil record of ostriches (and palaeognaths in general) being pretty dire. The heron-sized middle Eocene Palaeotis weigelti from Germany has been suggested to be a direct relative of ostriches but the evidence for this is equivocable (Mayr 2009). The earliest undoubted ostrich is the early Miocene Struthio coppensi from Namibia, and this is already similar enough to modern ostriches to be placed in the same genus.

Fossil ostriches are known from southeastern Europe to China, and survived across much of Asia until the Pleistocene. Several species have been named, but the usual vagaries of preservation make it debatable how many are distinct. Matters are complicated by several 'species', such as the Ukrainian Struthio chersonensis, that have been named based on fossil eggshells, raising questions as to whether such names can or should be applied to associated body fossils. Also unknown are the phylogenetic relationships between modern and fossil ostriches: whether the Eurasian ostriches represented a single or multiple dispersals out of Africa, or even whether ostriches may have originated in Eurasia*.

*It was suggested at one point that ostriches may have originally come from India, only dispersing to Africa after the subcontinent latched onto the rest of Eurasia. Support for this was based on the phylogenetic hypotheses that ostriches and the South American rheas formed an exclusive clade within the palaeognaths, and that the divergence of the flightless ratites was directly influenced by the division of the Gondwanan supercontinent (a South American-African connection being inconsistent with Africa being the first part of Gondwana to be separated). As support for both these arguments has declined, the need to somehow get ostriches out of Africa has evaporated.

The earliest known ostrich, the aforementioned Struthio coppensi, was a smaller and more slender bird than the modern ostrich, but some fossil species were larger. Perhaps the tallest ostrich species was S. oldowayi of the Tanzanian Pleistocene, which had a femur about a third as long again as the modern species. The femur of the Georgian Plio-Pleistocene S. dmanisiensis was not quite as long as that of S. oldowayi but it was considerably more robust, suggesting a proportionally solidly-built bird (Vekua 2013). Struthio brachydactylus (which sometimes moonlights as S. chersonensis) from the Miocene of Ukraine was also robustly built, albeit probably no taller (if not shorter) than a modern ostrich, but its main distinction lies in it taking the toe reduction seen in other ostriches even further. The fourth toe was reduced, with more weight placed on the third toe, making this species functionally almost single-toed (Boev & Spassov 2009).

REFERENCES

Boev, Z., & N. Spassov. 2009. First record of ostriches (Aves, Struthioniformes, Struthionidae) from the late Miocene of Bulgaria with taxonomic and zoogeographic discussion. Geodiversitas 31 (3): 493–507.

Burleigh, J. G., R. T. Kimball & E. L. Braun. 2015. Building the avian tree of life using a large-scale, sparse supermatrix. Molecular Phylogenetics and Evolution 84: 53–63.

Mayr, G. 2009. Paleogene Fossil Birds. Springer.

Robinson, T. J., & C. A. Matthee. 1999. Molecular genetic relationships of the extinct ostrich, Struthio camelus syriacus: consequences for ostrich introductions into Saudi Arabia. Animal Conservation 2: 165–171.

Vekua, A. 2013. Giant ostrich in Dmanisi fauna. Bulletin of the Georgian National Academy of Sciences 7 (2): 143–148.

Coscoroba

So what was the bird in Wednesday's photo? It didn't take long for it to be recognised for what it was, a coscoroba.

The coscoroba Coscoroba coscoroba, photographed by Christopher Valentine at the Jardin des Plantes, Paris. Photographing this animal was not entirely easy: it was in the process of preening, and every time that we tried to get a photo, its head would dive back into its feathers and we'd have yet another photo of a headless coscoroba.

The coscoroba (its name refers to the sound of its call) is a waterbird of coastward parts of southern South America, with its range having extended over the past century as far north as Uruguay (Kear 2005). In general appearance, it resembles a small swan (and is often called the 'coscoroba swan'). The most obvious difference between a swan and a coscoroba is that the latter lacks a bare patch of skin between its eyes and its beak. Coscorobas also have a flatter, more 'duck-like' beak than swans. Another significant difference can be seen in their behaviour: swans and geese are characterised by what is called a 'triumph ceremony', where a male approaches his partner (swans form life-long pair bonds), raising and lowering his head while calling, and is answered by her in kind. This behaviour is particularly common after the male has seen off a potential rival (hence the name), and probably serves to maintain the pair bond. Coscorobas, it seems, are far too refined for such brazen posturing, and limit themselves to a little quiet murmuring of their eponymous call (Johnsgard 1965).

Because of its 'not-quite-swannish' nature, the coscoroba has often been seen as a link between swans and some other group of waterfowl, such as geese or whistling ducks. Molecular studies (e.g. Donne-Goussé et al. 2002) have placed it as sister to the Cape Barren goose Cereopsis novaehollandiae of Australia, with the two together sister to the swans. This does seem a little counter-intuitive, as superficially Cereopsis does not appear very coscoroba-like, but it is relatively well-supported. The purported similarities between the coscoroba and whistling ducks, on the other hand, are quite possibly plesiomorphies retained from the ancestral waterfowl.

The Cape Barren goose Cereopsis novaehollandiae, potential sister to the coscoroba. Photographed by Norm Hanson.

REFERENCES

Donne-Goussé, C., V. Laudet & C. Hänni. 2002. A molecular phylogeny of Anseriformes based on mitochondrial DNA analysis. Molecular Phylogenetics and Evolution 23: 339-356.

Johnsgard, P. 1965. Handbook of Waterfowl Behavior. University of Nebraska: Lincoln.

Kear, J. 2005. Ducks, Geese and Swans. Oxford University Press.

Name the Bug #8: Prosobonia cancellata

Prosobonia cancellata - photo by Ron Hoff.

Prosobonia cancellata, the Tuamotu sandpiper, is a small to medium-sized bird found on a small number of coral atolls in French Polynesia. It is currently endangered with probably about 1200-1300 surviving individuals in 2003, mostly on the two islands of Tenararo and Morane (Pierce & Blanvillain, 2004). Zusi & Jehl (1970) included Prosobonia in the subfamily Tringinae, which also includes the Tringa sandpipers, Numenius (curlews) and Limosa (godwits). Prosobonia differs from these genera in living higher up on the shoreline, including the atoll forest, feeding on small invertebrates gleaned among leaf litter and off trees. They also seem to eat a reasonable amount of plant material such as seeds.

Other Prosobonia species were once found on a number of tropical Polynesian islands, while P. cancellata itself was previously more widespread with a range extending to Kiritimati (Christmas Island) in Kiribati. Some authors have regarded the Tuamotu and Kiritimati populations as separate subspecies or species, but Zusi and Jehl (1970) pointed out that the only known specimen from Kiritimati (unfortunately no longer available) probably lay within the known range of variation for Tuamotu specimens. Prosobonia leucoptera was found on Tahiti and Moorea (again, some authors have regarded the two populations as separate species) while undescribed subfossils have been found on Henderson, Marquesas and Cook Islands. Prosobonia cancellata has also been placed in a separate genus, Aechmorhynchus, from P. leucoptera, but again Zusi & Jehl established that significant differences between the two species were few except for coloration pattern (P. cancellata has barred plumage, while P. leucoptera was plainer) so there can be little doubt of their close relationship relative to other taxa.

REFERENCES

Pierce, R. J., & C. Blanvillain. 2004. Current status of the endangered Tuamotu sandpiper or titi Prosobonia cancellata and recommended actions for its recovery. Wader Study Group Bulletin 105: 93-100.

Zusi, R. L., & J. R. Jehl Jr. 1970. The systematic relationships of Aechmorhynchus, Prosobonia, and Phegornis (Charadriiformes; Charadrii). Auk 87: 760-780.

A Pathetic Plea for Recognition, and a Platypus-billed Duck

The closing date of submissions for this year's OpenLab, an annual collection of the year's best science-blog writting (as judged by the judges), is the 1st of December - a week from today. If there has been anything here at Catalogue of Organisms over the past year (since December the 1st last year), please (please!) submit it for consideration. Please! Go through the archive in the right sidebar, pick out your favourites, and make your contribution towards restoring my fragile sense of self-worth.

Otherwise, your humble host is still fairly knackered after getting back from the field yesterday (two weeks away = nearly three hundred e-mails [mostly spam], 1000+ entries on Google Reader, one pair crossed eyes). So just a brief finishing note:



This is the braincase of Talpanas lippa, a subfossil duck species, about the size of a mallard, described from Kauai by Iwaniuk et al. (2009) in Zootaxa today (and the article is freely available to all comers). As well as the braincase, Talpanas is also represented by pieces of jaw and leg bones and a partial pelvis. The name means "nearly blind mole-duck" - Talpanas would have had small, piggy little eyes, quite unusual in a bird, and would have almost certainly been nocturnal and flightless (flying blind is not usually recommended). Though the complete beak is still unknown, the available jaw pieces indicate that it would have been very broad. The leg bones indicate that Talpanas was a walker rather than a swimmer, so Talpanas was probably a forager for small invertebrates among forest litter; this is the lifestyle currently pursued by the kiwi, another nocturnal bird with relatively small eyes. Iwaniuk et al. suggest that Talpanas also resembled a platypus in using its broad bill to feel for invertebrates amongst the soil. The opening for the trigeminal nerve in the braincase is very large like that of a platypus (it's the opening labelled 'V' on the images above - take a look, it's freaking huge), indicating that Talpanas' bill would have been very sensitive to touch. Unfortunately, the skull of Talpanas is so unusual that its relationships with other anseriforms are obscure.

Cranes Off the Rails (Taxon of the Week: Grues)

The 'Messel rail' Messelornis cristata - a specimen with preserved plumage. Photo from here.

Despite its presentation in years of fieldguides and other popular books, the bird order 'Gruiformes' has in recent times been scattered to the four winds, with analyses both morphological and molecular proclaiming its polyphyly. Nevertheless, molecular analyses such as Hackett et al. (2008) continue to support a clade roughly corresponding to the suborder Grues as recognised by Cracraft (1973)* containing the cranes and the rails. The morphological analysis of Livezey & Zusi (2007) on the other hand, does not support this clade, but it does support monophyly for each of the two primary divisions within Grues, the ralloid and gruoid lineages.

*Just to confuse matters, the name "Grues" has been used by different authors for clades of differing inclusivity. Mayr (2009), for instance, uses "Grues" for the Aramus + Gruidae clade, and refers to the larger clade as "core Gruiformes".

The ralloid line contains the living families Rallidae*, the rails, and Heliornithidae, the finfoots (or should that be finfeet?) Cracraft (1973) regarded the Cretaceous Laornis edvardsianus as a stem ralloid, but no-one else seems to have taken him up on this suggestion. More reliably on the ralloid stem are the Palaeocene to Oligocene Messelornithidae (Mayr, 2009). Messelornithids were medium-sized birds (about the size of a small chicken) best known from Messelornis cristata for which over 500 specimens are available, some even with preserved feathering. Messelornis was highly terrestrialised with limited flight capabilities and almost ludicrously long legs (loss or reduction of flight has been a common occurrence among the Grues). Its beak was relatively short and the overall appearance of Messelornis would probably have not been dissimilar to the modern cariamas.

*Hackett et al. (2008) resolved the Rallidae as paraphyletic to Heliornithidae, with Sarothrura (the flufftails) closer to Heliornis than to the other two included rails Himantornis and Rallus. A few places, at least online, have suggested recognising Sarothrura as a separate family from the Rallidae as a result, but I'd recommend waiting for a more detailed analysis with greater coverage of the Rallidae. Increased taxonomic coverage may return the flufftails to the other Rallidae, or it may make it more appropriate to treat the finfoots as derived rallids.


The sungrebe Heliornis fulica of tropical South America (I tried to find a picture of one carrying chicks, but no luck). Photo by Jerry Oldenettel.

The finfoots of the Heliornithidae are three species (one in Asia, one in Africa, one in South America) of tropical grebe-like birds, renowned for their reclusiveness. The South American sungrebe Heliornis fulica is the most distinctive in appearance of the three species (though mitochondrial analysis indicates that it and the Asian Heliopais personata form a clade to the exclusion of the African Podica senegalensis - Fain et al., 2007) and is also very distinct in its nesting behaviour. Heliopais and Podica, like most aquatic birds, have chicks that hatch out reasonably well-developed and immediately able to swim after their parents. Heliornis, in contrast, has altricial chicks that hatch out after only ten to eleven days of incubation. The really amazing bit, though, is what happens after the chicks hatch. The male sungrebe has a shallow pouch under each wing and he is able to transport the chicks inside this pouch, even flying with them. Whether the chicks remain in the pouches permanently or whether they are only placed in them while the male is travelling remains unknown. Funnily enough, while this chick-carrying behaviour was described by Alvarez del Toro in 1971, it had originally been recorded almost 140 years earlier by Prince Maximilian of Wied. It seems that everyone else had assumed the prince was smoking something.


Grey-winged trumpeters, Psophia crepitans. Photo by A. Vinot.

The gruoid lineage includes Psophia, the trumpeters, Aramus guarauna, the limpkin, and Gruidae, the cranes, as well as the fossil taxa Parvigrus pohli, Geranoididae and Eogruidae. Most recent authors agree that Aramus and Gruidae form a clade to the exclusion of Psophia. The chicken-sized Oligocene Parvigrus was originally described by Mayr (2005) as sister to Aramus + Gruidae, but he later (Mayr, 2009) revised its position to stem gruoid. Parvigrus lacked the long beak of limpkins and cranes, as do the Recent trumpeters, three species of similarly chicken-sized birds found in northern South America.

Whether Geranoididae and Eogruidae possessed crane-like long beaks is an unknown factor as skull material for both has not been found. Cracraft (1973) placed both outside the crown gruoids, but Clarke et al. (2005) placed Eogruidae inside the gruoid crown as sister to Aramus + Gruidae. The Eocene Geranoididae have been described only from leg bones (Wetmore, 1933, assigned some wing bones to Geranoides jepseni in his original description of this species but did not describe them) so little can be said about them except that they were large and long-legged. Wetmore (1933) commented on the unusually wide spacing of the trochleae (the 'knuckles') at the end of the tarsometatarsus suggesting that Geranoides had very widely splayed toes, but Cracraft (1969) later attributed to wide spacing to post-mortem distortion. Cracraft (1969, 1973) included a number of Eocene birds in the Geranoididae but admitted a lack of derived characters uniting them; Geranoididae may represent a paraphyletic assemblage of basal gruoids.


Distal ends of tarsometatarsi of the eogruids Proergilornis and Ergilornis, showing reduction of the inner trochlea in Proergilornis and its loss in Ergilornis. Figure from Cracraft (1973).

The Eocene to Pliocene Eogruidae were also decent-sized long-legged birds from central Asia and (in later times) Europe. Earlier authors recognised two families, Eogruidae and Ergilornithidae, but 'ergilornithids' are now recognised as derived eogruids. Eogruids were highly cursorial birds and a humerus attributed to Ergilornis suggests that it was flightless, though the earlier Eogrus aeola shows no sign of being so (Clarke et al., 2005). Originally three-toed, eogruids showed a reduction in the size of the inner toe, and Ergilornis and Amphipelargus (the latest of the eogruids) lost it entirely (it is easy to present a progression from flying and three-toed to flightless and two-toed, but be warned that three-toed species survived into the Miocene, well after the appearance of the two-toed forms). The only other birds to reduce the number of toes to two are the ostriches, and a relationship between ostriches and eogruids has been suggested in the past (generally in association with the idea that the ratites do not form a monophyletic group). However, Cracraft (1973) confirmed that eogruids were more similar in their fine morphology to gruoids than ostriches, and modern phylogenetic analyses do not support a close relationship of ostriches and gruoids.

Many people carry the impression that flightlessness in birds is associated with lack of predators. However, eogruids evolved flightlessness in an environment in which predators were no rarity (amongst others, they shared their world with such horrors as hyaenodonts and entelodonts*). Similarly, while the exact circumstances in which they became flightless is unknown, modern ostriches (Africa), emus (Australia) and rheas (South America) all live alongside significant predators or at least did so until recently. Obviously, something other than lack of predators is at play here.

*I always imagine Roald Dahl's hornswogglers to be something like an entelodont.

REFERENCES

Clarke, J. A., M. Norell & D. Dashzeveg. 2005. New avian remains from the Eocene of Mongolia and the phylogenetic position of the Eogruidae (Aves, Gruoidea). American Museum Novitates 3494: 1-17.

Cracraft, J. 1969. Systematics and evolution of the Gruiformes (class, Aves). 1, The Eocene family Geranoididae and the early history of the Gruiformes. American Museum Novitates 2388: 1-41.

Cracraft, J. 1973. Systematics and evolution of the Gruiformes (class Aves). 3, Phylogeny of the suborder Grues. Bulletin of the American Museum of Natural History 151: 1-127.

Fain, M. G., C. Krajewski & P. Houde. 2007. Phylogeny of "core Gruiformes" (Aves: Grues) and resolution of the limpkin–sungrebe problem. Molecular Phylogenetics and Evolution 43: 515-529.

Hackett, S. J., R. T. Kimball, S. Reddy, R. C. K. Bowie, E. L. Braun, M. J. Braun, J. L. Chojnowski, W. A. Cox, K.-L. Han, J. Harshman, C. J. Huddleston, B. D. Marks, K. J. Miglia, W. S. Moore, F. H. Sheldon, D. W. Steadman, C. C. Witt & T. Yuri. 2008. A phylogenomic study of birds reveals their evolutionary history. Science 320: 1763-1768.

Livezey, B. C., & R. L. Zusi. 2007. Higher-order phylogeny of modern birds (Theropoda, Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion. Zoological Journal of the Linnean Society 149 (1): 1-95.

Mayr, G. 2005. A chicken-sized crane precursor from the early Oligocene of France. Naturwissenschaften 92: 389-393.

Mayr, G. 2009. Palaeogene Fossil Birds. Springer.

Wetmore, A. 1933. Fossil bird remains from the Eocene of Wyoming. Condor 35: 115-118.

The Voice of the Turtle (Taxon of the Week: Streptopelia)

Eurasian collared dove Streptopelia decaocto, the most widespread Streptopelia species in Europe. Photo by Rovdyr.

The bird genus Streptopelia comprises the turtledoves or collared doves - thirteen to seventeen species (depending on preferred generic boundaries) of medium-sized, generally pinkish birds that have long garnered human admiration due to their attractive appearance and cooing vocalisations. The name "turtledove" is derived from the Latin turtur, which is itself an imitation of the sound made by the doves. The calls of different species of turtledoves are distinct, and often play a significant part in their identification (Slabbekoorn et al., 1999). Streptopelia doves are native to Africa and the warmer parts of Asia and Europe, but a number of species have been introduced to other parts of the world. Here in Perth, for instance, the laughing dove S. senegalensis and the spotted dove S. chinensis are both abundant (the former particularly so), while S. chinensis is also a successful exotic in Auckland back in New Zealand. Also widely introduced is the African collared dove or Barbary dove Streptopelia risoria*.

*The Barbary dove ("S. risoria") is the domesticated form of the African collared dove ("S. roseogrisea"), and most modern authors no longer regard the two as specifically distinct. S. risoria Linnaeus, 1758 has priority over S. roseogrisea Sundevall, 1857. However, it has become common practice for the name based on a "wild" taxon to be given preference over one based on a domestic taxon because of the often complicated nature of taxonomic concepts in relation to domesticated animals (Gentry et al., 2004), and so many authors have preferred to use S. roseogrisea for the combined taxon. A recent proposal to formalise this situation was turned down by the ICZN (ICZN, 2008), leaving S. risoria as the valid name for this species.


The Madagascar turtle dove Streptopelia picturata (aka Nesoenas picturata). Phylogenetic analysis indicates that this species is closely related to the pink pigeon Nesoenas mayeri (=Streptopelia mayeri) of Mauritius. Though distinct morphologically, the two species have very similar vocalisations. Photo from here.

In the past, Columbidae (pigeons and doves) have mostly been divided between two subfamilies, the Columbinae (standard columbids) and Treroninae (fruit-pigeons and fruit-doves), with separate monogeneric subfamilies for the morphologically distinctive genera Goura and Didunculus (and sometimes Otidiphaps) and a separate family Raphidae for the extinct dodo Raphus cucullatus and solitaire Pezophaps solitaria. This arrangement, never particularly sturdy at the best of times, has been blown out of the water by recent analyses (Pereira et al., 2007), which render the traditional Columbinae paraphyletic to the other subfamilies and Raphidae while the Treroninae becomes polyphyletic. To date, no-one has formally proposed a revised subfamilial classification of Columbidae, though Pereira et al. (2007) did recognise three well-supported clades in the family which they called simply A, B and C*.

*Because I have the comfort of knowing that no-one is going to take any notice of me in this matter, I can reveal that if we were to recognise these three clades as a subfamily each, they would become respectively Columbinae, Claravinae and Raphinae (going by the dates reported in Bock, 1994), and I find a certain pleasant irony in the idea that Raphinae would be the largest of the three.


The collared dove Streptopelia chinensis (=Stigmatopelia chinensis). Originally native to eastern Asia, the collared dove has been widely introduced elsewhere in the world. Photo by Charles Lam.

Whatever the eventual division of the family, Streptopelia will almost certainly remain a part of Columbinae, as it is the most closely related genus to Columba. Molecular analysis of fourteen of the sixteen species generally included in Streptopelia by Johnson et al. (2001) identified three main clades in the genus - a large clade containing the majority of species, a clade uniting S. chinensis and S. senegalensis, and a clade containing the Madagascan S. picturata and the pink dove Nesoenas mayeri of Mauritius. This three-part division is also reasonably consistent with morphological and vocal distinctions within the genus. The two smaller clades were in turn sister to each other, but the monophyly of Streptopelia as a whole was not proven; depending on the chosen method of analysis, either Streptopelia was monophyletic (the maximum likelihood results) or the main Streptopelia clade was sister to a clade containing Old World Columba and the two smaller clades (the maximum parsimony results). New World 'Columba' species were the sister clade to Streptopelia plus Old World Columba whatever the method; their recognition as a separate genus Patagioenas was proposed. Johnson et al. (2001) chose to retain Streptopelia in its previous circumscription, but with 'Nesoenas' mayeri also included. In contrast, Cheke (2005) suggested restricting Streptopelia to the main clade and recognising the smaller clades as separate genera Nesoenas (for mayeri and picturata) and Stigmatopelia (for chinensis and senegalensis). Johnson et al.'s (2001) system has the advantage of minimising the number of name changes involved; Cheke's (2005) system is potentially more robust to the uncertain monophyly of the broader Streptopelia; only time will tell which gains the greater popularity.

REFERENCES

Bock, W. J. 1994. History and nomenclature of avian family-group names. Bulletin of the American Museum of Natural History 222: 1-281.

Cheke, A. S. 2005. Naming segregates from the Columba–Streptopelia pigeons following DNA studies on phylogeny. Bulletin of the British Ornithologists' Club 125 (4): 293-295.

Gentry, A., J. Clutton-Brock & C. P. Groves. 2004. The naming of wild animal species and their domestic derivatives. Journal of Archaeological Science 31: 645-651.

ICZN. 2008. Opinion 2215: Streptopelia risoria (Linnaeus, 1758) (Aves, Columbidae): priority maintained. Bulletin of Zoological Nomenclature 65 (4).

Johnson, K. P., S. de Kort, K. Dinwoodey, A. C. Mateman, C. ten Cate, C. M. Lessells & D. H. Clayton. 2001. A molecular phylogeny of the dove genera Streptopelia and Columba. Auk 118 (4): 874-887.

Pereira, S. L., K. P. Johnson, D. H. Clayton & A. J. Baker. 2007. Mitochondrial and nuclear DNA sequences support a Cretaceous origin of Columbiformes and a dispersal-driven radiation in the Paleogene. Systematic Biology 56 (4): 656-672.

Slabbekoorn, H., S. de Kort & C. ten Cate. 1999. Comparative analysis of perch-coo vocalizations in Streptopelia doves. Auk 116 (3): 737-748.

Oh Crake (Taxon of the Week: Amaurornis)

The white-breasted waterhen, Amaurornis phoenicurus, one of the more widespread and distinctive Amaurornis species. Phot from here.

The Rallidae are undeniably a very successful group of birds. Rallids have spread to almost every corner of the globe, including a few island corners that were never reached by other terrestrial birds. The subject of today's post is one of the widespread genera of rallids - but it's one of the trickier ones.

Stable classification of rallids has eluded ornithologists for years, for two main reasons. One is that rallids are a prime example of what may be called the smudge effect - clearly distinct subgroups, but without clear boundaries. Take a rail and a moorhen, and the differences are easy to spot. But then someone comes along with a third species, that looks a bit like a rail and a bit like a moorhen, and it's back to the bench for the frustrated ornithologist. The other is the unusual nature of rallid evolution and dispersal. Rallids are, normally, surprisingly good fliers - that's why they are able to reach so many remote islands. On the other hand, they tend to be very reluctant fliers, only invoking those flying abilities if they absolutely have to. As a result, rallids have tended to disperse to remote localities, and then promptly lost the flying abilities that got them there at the first available opportunity. With those losses of flying ability come other related changes - larger body size and such - resulting in the flightless rails looking not very much like their flying descendants, and an awful lot like unrelated flightless species from completely different islands.


The plain bush-hen of the Philippines, Amaurornis olivacea, type species and fairly typical of the brown species of the genus. Photo taken from here - and while you're at it, click through and take a look at the photo of the peacock-pheasant. Seriously, some birds are so incredible they just beggar belief.

The genus Amaurornis belongs to the subgroup of rallids known as the crakes. Crakes are quite generalised rallids, distinguished from the other major generalised rallid group, the rails, by their shorter beaks. Most crakes are notoriously shy and retiring birds - as an example of their reserve, one crake species, Amaurornis magnirostris of the Talaud Islands in Indonesia, was only described in 1998 (Lambert, 1998). The crake species assigned to Amaurornis, also known as bush hens or water hens, tend to be larger than other crake species in the genus Porzana and its satellite genera. Other than this, however, there seems to have been little or no definition on what actually distinguishes one genus from the other, and species have been shuttled back and forth between the two for years.

Indeed, Olson (1973) regarded Amaurornis as the generalised ancestral group for a number of other rallid genera, including Porzana, Porphyrio (swamphens), Gallinula (moorhens) and Fulica (coots) - effectively paraphyletic, except that he didn't suggest any specific relationships between descendant genera and particular species within Amaurornis. As well as the Asian and Australasian species previously included in the genus, Olson (1973) also assigned three African species previously regarded as the genus Limnocorax to Amaurornis.


The brown crake, Limnocorax akool - long included in Amaurornis, but, it seems, not belonging there after all. Photo by Nikhil Devasar.

The first explicitly phylogenetic analysis of the Rallidae (and still the only morphological analysis of the group) was the gigantic production of Livezey (1998). Livezey confirmed Olsen's suggestion of a close relationship between Amaurornis, Porzana, Gallinula and Fulica (but not Porphyrio), but Porzana was massively paraphyletic, with the other three genera belonging to a clade that was nested within Porzana - specifically within the subgenus Limnocorax (which Livezey had removed from Amaurornis and returned to Porzana so that at least one of the genera could be monophyletic). Livezey refrained from carving up Porzana into bite-sized monophyletic chunks because support for the recovered relationships within the genus was negligible, and while he did support monophyly for the core group of Amaurornis, it apparently didn't take much fiddling with the analysis to make the whole thing topple over like a badly-cooked soufflé (certainly, Livezey's taxonomic separation of Amaurornis from the other crakes as a separate subtribe Amaurornithina fits right into the "tits on a bull" category). There are also hints that convergence may have befuddled a number of results of the Livezey analysis - elsewhere in the tree, for instance, was a highly suspect clustering of flightless taxa from New Zealand and Mauritius.

Subsequent molecular analyses have tackled sections of the Rallidae, but unfortunately none have had the coverage of the Livezey (1998) analysis. The most significant for the crakes has been that of Slikas et al. (2002), which answered the hanging question of "is Porzana or Amaurornis the polyphyletic genus?" with "As it happens, they both are". Their analysis divided Porzana and Amaurornis between three clades - one containing species of the former, one containing species of the latter, and one containing species of both. Christidis & Boles (2008) proposed that the names Porzana and Amaurornis be each restricted to the appropriate one of the first two clades, with the third clade recognised as a third genus. Oh, and the correct name for that third genus just happens to be Limnocorax. That's right - after years of being the subject of a game of taxonomic kickball, Limnocorax breaks free to become its own genus - and one considerably larger than either of the other two. Unfortunately, Slikas et al. didn't include any representatives of Gallinula or Fulica to test where they sat relative to the three clades.


John Gould's painting of Megacrex inepta - this flightless New Guinea bird may be an Amaurornis, or it may be something else entirely. Image from here - I don't normally link to sites selling stuff, but I suspect this one doesn't count as I doubt many of my readers have a spare $875 lying around to spend on a picture of a bird anyway.

If we accept the results of Slikas et al. (2002), Amaurornis includes five species from southern and south-east Asia and northern Australasia - A. olivacea, A. isabellina, A. phoenicurus, A. moluccana and A. magnirostris*. Most of these are some variation on chestnut-brown, but the striking white-breasted A. phoenicurus is a notable exception. An unfortunate omission from Slikas et al.'s (2002) analysis was the large New Guinean flightless rail Megacrex inepta, which was placed in Amaurornis by Livezey (1998). A molecular analysis by Trewick (1997) that included Megacrex placed it in association with Rallus and its relatives (the rails), and far away from Porzana, but (a) none of the other "Amaurornis" species were included in this analysis, and (b) it was a neighbour-joining analysis. Yuck.

*Brief taxonomic note - Amaurornis is one of those genera that has been subject to argument about whether it is masculine or feminine. It's feminine, so the species names have to be formed accordingly (phoenicurus retains the masculine ending because it's a noun, not an adjective).

REFERENCES

Christidis, L., & W. Boles. 2008. Systematics and Taxonomy of Australian Birds. CSIRO Publishing.

Lambert, F. R. 1998. A new species of Amaurornis from the Talaud Islands,
Indonesia, and a review of taxonomy of bush hens occurring from the
Philippines to Australasia. Bulletin of the British Ornithologist’s Club 118 (2): 67 – 82.

Livezey, B. C. 1998. A phylogenetic analysis of the Gruiformes (Aves) based on morphological characters, with an emphasis on the rails (Rallidae). Philosophical Transactions of the Royal Society of London Series B – Biological Sciences 353: 2077-2151.

Olson, S. L. 1973. A classification of the Rallidae. Wilson Bulletin 85 (4): 381-416.

Slikas, B., S. L. Olson & R. C. Fleischer. 2002. Rapid, independent evolution of flightlessness in four species of Pacific Island rails (Rallidae): an analysis based on mitochondrial sequence data. Journal of Avian Biology 33: 5-14.

Trewick, S. A. 1997. Flightlessness and phylogeny amongst endemic rails (Aves: Rallidae) of the New Zealand region. Philosophical Transactions of the Royal Society of London Series B – Biological Sciences 352: 429-446.

Jonathon Livingstone's Cousin (Taxon of the Week: Sterna)

The Arctic tern, Sterna paradisaea. This is the species famed for making the longest annual migration of any bird, all the way from the Arctic to the Antarctic. Photo by Roberto Lerco.

The terns are the gulls' more refined relations. They have become superb aerialists, spending most of their lives on the wing, feeding on fish delicately plucked from the water's surface as they fly above. Depending on where you look, the clade that the terns comprise may be dubbed the Sternini, Sterninae or Sternidae, but this is purely a quibble over ranking - there seems to be no disagreement about what is, or isn't, a tern.

At the lower level (naturally), a little more disagreement ensues. There is a clear distinction between the mostly smaller, tree-nesting tropical noddy terns of the genera Anous, Gygis and Procelsterna (sometimes all combined in Anous) and the larger, ground-nesting true terns of Sterna and related genera. The spectacular cave-nesting Inca tern, Larosterna inca, also seems to be universally placed in its own genus. However, authorities differ on whether they would prefer to include all the ground-nesting terns in a single genus Sterna, or whether they would prefer to peel off some of the more distinctive taxa into what might be called Sterna's satellite genera, such as Hydroprogne caspia* (the Caspian tern), Chlidonias (the marsh terns) or Gelochelidon nilotica** (the gull-billed tern).

*Hydroprogne, as it happens, translates into English as "water swallow", which seems a rather apropos description for any tern..

**As well as being morphologically distinct, Chlidonias and Gelochelidon (the "laughing swallow") both differ from most other terns in being much more likely to be found inland. Here in Australia, Gelochelidon nilotica can travel almost to the centre of the continent, visiting temporary salt lakes when they are filled by the rains. There is something very surreal about being in the centre of the desert, hundreds of kilometres from the coast, and looking up to see terns passing overhead.


The New Zealand fairy tern, Sternula nereis davisae. With a surviving population of only about thirty-five individuals, this is one of the world's rarest terns, and indeed one of the rarest of all birds. Photo by John Kendrick.

The only proper phylogenetic study that appears to have been published recently on terns was a mitochondrial DNA analysis by Bridge et al. (2005). Sternini were also included in the supertree analysis of Charadriiformes by Thomas et al. (2004), but a look through their source trees suggests that their data for Sternini were almost entirely derived from a 1984 PhD thesis. Bridge et al. (2005) found that Larosterna inca was nested well within Sterna sensu lato, and suggested the recognition of nine genera within this clade (including Larosterna) - as well as those already mentioned, these were Onychoprion for the brown-winged terns, Sternula for the little terns, Phaetusa simplex (the large-billed tern) and Thalasseus for the crested terns, with Sterna restricted to a group labelled the "typical black-capped terns". Most of the genera recognised by Bridge et al. (2005) correspond to groups recognised previously on morphological grounds. The one arguable exception is, ironically enough, their Sterna sensu stricto, which also remained poorly supported in Bridge et al.'s analysis, though a smaller core of species within Sterna was well-supported.


Phylogeny of terns from Bridge et al. (2005). Note that, with only two exceptions, the colour pattern of the head corresponds closely with the phylogeny, though beak coloration appears to be more labile.

One interesting detail of Bridge et al.'s results is how closely the proposed phylogeny correlates with patterns of breeding plumage coloration on the head (it is worth noting that the two exceptions, Sterna sumatrana and S. trudeaui, have breeding plumages similar to the non-breeding plumages of related species). On the other hand, the correlation drops significantly when one considers overall coloration. This is most obvious in the genus Chlidonias - the great similarity in the head views of Chlidonias species in the figure above disguises the fact that these four species vary from almost entirely black (Chlidonias niger) to mostly white with only the cap of the head black (Chlidonias hybrida)*. The main point is that while there is a common assumption that colour patterns are a priori of little use as characters for phylogenetic analysis because they are supposedly too evolutionarily labile, this is not necessarily the case. Some details of colour pattern may indeed be very variable and prone to homoplasy, others may prove to be evolutionarily very conservative (and what is labile in one clade might be conservative in another) - much as one might find in just about any other possible character complex.

*As an aside, a comparison of different sources suggests that there has been confusion over whether the genus Chlidonias is masculine or feminine (and hence what is the appropriate spelling for the species in this genus). According to David & Gosselin (2002), Chlidonias is masculine - hence C. niger, C. leucopterus and C. albostriatus, but C. hybrida, because in this case "hybrida" is a noun in apposition, not an adjective. Thanks are due to Alan Peterson's Zoonomen page for clearing this up.

REFERENCES

Bridge, E. S., A. W. Jones & A. J. Baker. 2005. A phylogenetic framework for the terns (Sternini) inferred from mtDNA sequences: implications for taxonomy and plumage evolution. Molecular Phylogenetics and Evolution 35: 459-469.

David, N., & M. Gosselin. 2002. Gender agreement of avian species names. Bulletin of the British Ornithologists' Club 122 (1): 14-49.

Thomas, G. H., M. A. Wills & T. Székely. 2004. A supertree approach to shorebird phylogeny. BMC Evolutionary Biology 4: 28.

More From the "They Don't Write Papers Like They Used To" Files

But before that, a couple of other things:

Recent Carnivals - Berry Go Round is here, Circus of the Spineless is here.

Also recently, the Open Laboratory 2008 collection of some of the year's best online science writing is now available. In the interests of disclosing all interests (naturally), yours truly has a piece featured in this publication - on citrus fruit. Anybody who has heard me commenting on my poor knowledge and outright terror of botany will know that this is a Very Funny Thing.

On to the main point of the post, which will not be anything I'm writing at all...

Recently, I was reading a paper from 1866 by a Dr H. Dohrn with the unprepossessing title of "Synopsis of the birds of Ilha do Principe, with some remarks on their habits and descriptions of new species" (Proceedings of the Zoological Society of London 1866: 324-332). Principe, for those who don't know it, is a part of the country of Sao Thomé and Principe in west-central Africa. This is the second paragraph of that publiction:

It seems to me that the most remarkable feature in the fauna of Ilha do Principe is that not a single bird of prey exists on the island, whilst they are abundant on the two other islands and on the nearest part of the continent. I saw hundreds of Milvus parasitus in San Thomé; Gypohierax angolensis and some other species are not uncommon in Fernando Po; but the whole tribe avoids Principe. The inhabitants of the latter place and of San Thomé assert that there is a deadly hatred between the Grey Parrots (Psittacus erythacus) of Principe and the Kites of San Thomé, and that, if ever a Milvus visits the neighbouring island, hundreds of Parrots fall upon him and kill him, and that the Kites take revenge if perchance a Parrot should venture a trip to their kingdom. There must be some family reason for this strange degree of enmity, for they seem to live in tolerable peace together on the coast.

You will probably not be surprised to hear that I was somewhat taken aback by this - even allowing for the different time period, it seemed a rather credulous account. But as I read further, I realised that Dohrn was employing something that is a little alien to modern academic writing: irony.

To demonstrate my point, here are my other favourite passages from Dohrn:

On a species of drongo:

The native name is "Maria Palu, feiticeira" (translated, Maria Palu, the sorceress). The bird is black, with red eyes; seems very indolent in daytime, and shows a great ability in the imitation of some other birds' voices. Of course there must be some "feiticeira" to it: therefore, sitting on the roof of a house and singing in its melancholy manner, it prophecies the death of one of the inhabitants; and this, of course, takes place, but often a long time after this prophecy.

On the bald ibis:

Soon after my arrival on the island I was informed by some natives that there was a very remarkable bird in the island called "Corvão." One told me that it was a kind of raven with splendid metallic wings; another described the bird "with the head of an owl and the feet of a duck, climbing up and down trees;" and others gave me other extravagant descriptions of it; but all of them agreed that the bird lived in almost inaccessible rocky and wooded localities of the southern district, and that if ever a specimen passed over the town it was a bad omen for the white inhabitants, who in such case were exposed to heavy disease or death. Of course I was very curious to see this species, and settled for a fortnight in a negro's hut in those desert parts of the island*. Whoever has visited those large tropical forests knows the difficulty of proceeding there. I enjoyed the special favour of heaven in arriving there when the rains set in a month before they usually do, and it was very hard work to run after these birds. I saw them daily at great distances, and heard them crowing like a Raven; but as soon as I entered the forests the monkeys made so much noise, barking and howling, as to alarm all the animals in the neighbourhood. Thus I was finally very glad when one of my native hunters appeared with a female specimen of the Corvão, which turned out to be Geronticus olivaceus.

*I think in this case "desert" means "deserted", not "arid".

Boobies

The northern gannet (Morus bassanus). Photo by Alan Wilson.

The Taxon of the Week post is a day late this week because, of course, yesterday was a public holiday here in Australia (as far as I can make it out, it seems a bunch of poms were so glad to see land after six months in a leaky boat [trying hard to keep afloat] that they've been celebrating ever since - the people already here may have had a different view of matters, but nobody ever asked them). Not only is it late, but it'll be short, too, because the Taxon of the Week is the Sulidae, which has been covered only recently by Darren Naish (here and here) with all the innuendo that is unavoidable when dealing with a group of birds going by the common name of "boobies" (though he did omit mentioning the close connection between boobies and shags).

The Sulidae are the boobies and gannets, a small but fairly cosmopolitan assortment of seabirds. Among the living sulids, the gannets form the genus Morus, and most boobies belong to the genus Sula. The exception is Abbott's booby (Papasula abbotti) which was originally included in Sula, and is still commonly referred to as such (at least in popular sources), but sits on the gannet rather than the booby side of the divergence between the two main genera (Friesen & Anderson, 1997). The distinctions between the three genera are not huge, and some authors in the past have referred to all living sulids as Sula. In the recent fauna there is a clear geographical division between gannets and boobies - Morus is found in the northern and southern temperate zones while Sula and Papasula are tropical or subtropical - but this does not appear to have always been so in the past. The Pliocene Pisco Formation of Peru has provided species assigned to both Sula and Morus (Stucchi & Urbina, 2004).


A sulid on the Galapagos Islands. This photo comes from here, where it is identified as a masked booby (Sula dactylatra). I don't think it is - the orange beak identifies it as a Nazca booby (Sula granti), a species that was only distinguished from S. dactylatra in 1998 (Pitman & Jehl, 1998). Don Roberson's site has a photo by Bob Pitman of the two species standing side by side to show the difference.

Eight fossil genera have been assigned to Sulidae (as well as fossil species of Sula and Morus*) - the Eocene Masillastega and Eostega, the Oligocene Empheresula, the Miocene Microsula (now a synonym of Morus), Miosula, Enkurosula and Sarmatosula, and the Pliocene Palaeosula and Ramphastosula. The Cretaceous Elopteryx did a stint as a close relative of the sulids, but is now regarded as a dinosaur of the Troodontidae and not even a bird (for most definitions of the word "bird"). Eostega lebedinskyi is known from a single mandible that was recently redescribed by Mlíkovský (2007), who reasserted its sulid nature (past authors have disagreed). Masillastega rectirostris is known from a skull from the famed Messel formation, and differs from living sulids in having a comparatively long beak (Mayr, 2002). It is also distinct in having seemingly inhabited a freshwater environment, while all modern species are exclusively marine. Mayr (2002) only tentatively regarded Masillastega as a sulid, and it may be a stem-member of the family (Mayr, 2005). Mlíkovský (2007) synonymised the two Eocene genera on the basis of a lack of significant differences between them.

*Apart from a single taxon described as a subspecies of the modern species (Papasula abbotti costelloi [ha ha]), there don't appear to be any fossil species assigned to Papasula. Considering the only recent distinction of Papasula from Sula, one wonders whether any fossils of the former are masquerading as the latter.

Empheresula arvernensis is represented by a pelvis from France (the original material also included a sternum, but Lambrecht later indicated that the sternum was not even sulid - Mlíkovský, 2002). The French Oligocene also provided Sula ronzoni, which, if correctly assigned (which seems to be debatable*), would suggest that the living sulid lineages had diverged by that point (Friesen & Anderson, 1997, used a molecular clock to estimate a divergence time for Sula vs. Morus/Papasula of 23 million years ago, which is also consistent with this, but the age calculation methods used by Friesen & Anderson can only be described as [ahem] dated). The European Miocene genera Enkurosula and Sarmatosula are both known from isolated humeri, and are both doubtfully distinct from Morus (Nelson, 2006; Olson, 1984, suggests that Microsula (=Enkurosula) pygmaea may be conspecific with the contemporaneous Microsula avita of Maryland in the United States, which has itself been since reassigned to Morus), as are the Californian genera Miosula and Palaeosula.

*I'm rather confused here. Nelson (2006) notes that Sula ronzoni has four notches on the sternum, and indicates that this would place it on the sulid stem. However, Mlíkovský (2002, 2007) states that the type material of S. ronzoni is an incomplete pelvis, so what is Nelson talking about?



The wierdest of all sulids, though, is the Pliocene Peruvian Pisco Formation's Ramphastosula ramirezi. The genus name means "toucan-booby" and is undeniably appropriate as Ramphastosula, instead of having a dagger-like straight beak like all other sulids, had a deep beak with a distinct arch as shown in the reconstruction above from Stucchi & Urbina (2004). The skull of Ramphastosula is also more robust than in other sulids, seemingly to support the enlarged beak. Ramphastosula was obviously pursuing a different lifestyle to other sulids, as it looks as if it would be ill-suited to catching fish by plunge-diving. Stucchi & Urbina (2004) suggest that its robust skull indicates greater diving ability than other sulids, so perhaps Ramphastosula was more inclined to pursue its prey underwater than its modern relatives. Unfortunately, no post-cranial material is known as yet for this species.

REFERENCES

Friesen, V. L., & D. J. Anderson. 1997. Phylogeny and evolution of the Sulidae (Aves: Pelecaniformes): a test of alternative modes of speciation. Molecular Phylogenetics and Evolution 7 (2): 252-260.

Mayr, G. 2002. A skull of a new pelecaniform bird from the Middle Eocene of Messel, Germany. Acta Palaeontologica Polonica 47 (3): 507-512.

Mayr, G. 2005. The Paleogene fossil record of birds in Europe. Biological Reviews 80: 515-542.

Mlíkovský, J. 2002. Cenozoic Birds of the World. Part 1: Europe. Ninox Press: Praha.

Mlíkovský, J. 2007. Taxonomic identity of Eostega lebedinskyi Lambrecht, 1929 (Aves) from the middle Eocene of Romania. Annalen des Naturhistorischen Museums in Wien 109A: 19-27.

Nelson, J. B. 2006. Pelicans, Cormorants, and Their Relatives: The Pelecaniformes. Oxford University Press.

Olson, S. L. 1984. A brief synopsis of the fossil birds from the Pamunkey River and other Tertiary marine deposits in Virginia. In Stratigraphy and Paleontology of the Outcropping Tertiary Beds in the Pamunkey River Region, Central Virginia Coastal Plain: Guidebook for the Atlantic Coastal Plain Geological Association 1984 field trip (L. W. Ward & K. Krafft, eds.) pp. 217-223. Atlantic Coast Plain Geological Association.

Pitman, R. L., & J. R. Jehl, Jr. 1998. Geographic variation and reassessment of species limits in the "masked" boobies of the eastern Pacific Ocean. Wilson Bulletin 110: 155-170.

Stucchi, M., & M. Urbina. 2004. Ramphastosula (Aves, Sulidae): a new genus from the early Pliocene of the Pisco. Journal of Vertebrate Paleontology 24 (4): 974–978.