Tuesday 27 January 2009

Superb Birds

Superb starling
Lamprotornis superbus Rüppell, 1845
Sturnidae; Passeriformes; Aves; Chordata
London Zoo
November 2008

The above photo of a superb starling was taken in the “Birds of Africa” aviary at London Zoo, which contains Abdim’s storks (Ciconia abdimii), hamerkops (Scopus umbretta), Madagascar teals (Anas bernieri) and various turacos (Musophagidae) amongst other birds, in a mesh-covered walk-through area with pool and waterfall. As a result of the lack of bars or fingerprint-smeared glass, and the relative boldness of the aviary’s inhabitants, I was able to get this gorgeous picture of a superb starling, originally from East Africa, whose iridescent blue-green-purple and ginger plumage gave it its name. Incidentally, I always found it laughable that the masculine Latin for “superb” is superbus, which of course sounds like “super bus”.

Superb parrot
Polytelis swainsonii (Desmarest, 1826)
Psittacidae; Psittaciformes; Aves; Chordata
Van Hage Garden Centre
November 2008

Also known as the Barraband parakeet, the superb parrot is endemic to eastern Australia and is considered Vulnerable by the IUCN. It is mostly green, as you can see here, with a long tail, which you can’t.

Superb birds-of-paradise (stuffed)
Lophorina superba (Pennant, 1781)
Paradisaeidae; Passeriformes; Aves; Chordata
Cambridge Zoology Museum
June 2008

It is not easy to see when you look at a male bird-of-paradise that it is just a glorified crow. Females, however, look more corvine than their drag queen-like mates, and sound like ravens too. The superb bird-of-paradise is no more superb looking than any other of its more well known relatives, except for the beautiful iridescent cape that the male can lift under his throat to impress potential mates. It is one of the most widespread and abundant members of the Paradisaeidae, being found throughout most parts of the island of New Guinea, where most other birds-of-paradise are found.

Superb lyrebird (stuffed)
Menura novaehollandiae Latham, 1801
Menuridae; Passeriformes; Aves; Chordata
Natural History Museum, London
February 2008

Made semi-famous for its uncanny ability to mimic all sorts of natural and man-made sounds by its appearance in David Attenborough’s Life of Birds around a decade ago, the superb lyrebird is more well known to those who know it for the male’s beautiful tail, from whence the name comes. The resemblance to a lyre is clear; there are two long and broad feathers on the outside of the tail, and several filamentous plumes in between, like the strings of a lyre. Its ability to mimic other sounds has given its name an unintentional double meaning; should “lyre” be respelled “liar”?

Moving away from living dinosaurs and onto the extinct ones: there is a new palaeo-art themed carnival coming soon!

The theme, as you can see, is Ceratopsians, the horned dinosaurs. Check out the linked ad for more information, and stay tuned for exciting news related to palaeo-art...

I'm working on my entries... now get on with yours!

Wednesday 14 January 2009

Poisonous Pitohuis

This is a first for me; I am blogging about a research paper I have recently read. One of the perks of working in the greatest library in the world, ever, is the freedom to access any book or journal I want or need to. I was browsing the latest Molecular Phylogenetics and Evolution, and the title of this paper leapt out at me: Phylogeny of the avian genus Pitohui and the evolution of toxicity in birds. Toxicity in birds? I had known that the pitohui and some other birds have been known to have poisonous skin, but wanted to know more.

Above illustration by Mo Hassan, January 2009

Top left:
Hooded pitohui
Pitohui dichrous Bonaparte, 1850
Pachycephalidae; Passeriformes; Aves; Chordata

Bottom left:
Variable pitohui
Pitohui kirhocephalus (Lesson & Garnot, 1827)
Pachycephalidae; Passeriformes; Aves; Chordata

Top right:
Crested pitohui
"Pitohui" cristatus (Salvadori, 1875)
Pachycephalidae; Passeriformes; Aves; Chordata

Middle right:
Rusty pitohui
"Pitohui" ferrugineus (Bonaparte, 1850)
Pachycephalidae; Passeriformes; Aves; Chordata

Bottom centre:
Blue-capped ifrita
Ifrita kowaldi (De Vis, 1890)
Pachycephalidae; Passeriformes; Aves; Chordata

Bottom right:
Little shrike-thrush
Colluricincla megarhyncha (Quoy & Gaimard, 1830)
Pachycephalidae; Passeriformes; Aves; Chordata

The paper (Dumbacher et al., 2008) begins by introducing the pitohuis and the family Pachycephalidae, jay-like birds from Indonesia and Australasia. The authors then mentions that the pitohuis were found to be poisonous, secreting batrachotoxins (the same compound that is found in the toxins of poison-dart frogs and the fugu) through their skin. The toxins affect the nervous system by disabling the pathways of nervous signals. The birds have this compound probably to protect them from both predators and external parasites.

It isn’t just the pitohuis that are toxic; the blue-capped ifrita* was also found to be poisonous, but was considered only distantly related to the pitohuis; both are members of the same group that includes such different-looking birds as crows, drongos and birds-of-paradise, the Corvoidea. The ifrita had already proved difficult to pigeonhole, as various taxonomic studies placed the bird with such disparate families as the babblers, quail-thrushes, logrunners or fairy-wrens. The question was raised whether the ifrita and the pitohuis evolved the ability to secrete batrachotoxins independently, or whether their common ancestor at the base of the Corvoidea had this ability. This hypothesis was tested in this study, as well as the idea that toxicity is coupled with bright coloration.

*See this post from Darren Naish’s Tetrapod Zoology for a bit of background on the ifrita.

The genus Pitohui has been considered monophyletic (of one origin) since at least 1881, and all but one of them have been found to possess the toxins. They were known for being the “leaders” in mixed-species flocks, choosing where to feed, whilst being followed by other birds of different types. The possibility of Batesian or Müllerian mimicry taking place in these flocks is considered; Batesian mimicry is the mimicry of a poisonous species by an innocuous one (as in the monarch and viceroy butterflies); Müllerian mimicry is the co-mimicry of two unrelated poisonous species (like Heliconius butterflies).

The authors mention previous studies on the Pachycephalidae, but they note that none of them have been thorough, sampling few species, and none of the members of monotypic genera (those with only one species), none of which were known to be toxic. The complication is exacerbated further by the fact that other related families, such as the monarch flycatchers, have been difficult to analyse using phylogenetics.

A bird called the greater melampitta (Melampitta gigantea) was also analysed in this study, to find its place in the Passeriformes. Other corvoid species that were analysed include taxa which act as an outgroup, helping the phylogenetic tree to take shape. What the taxa all have in common is that they have all been considered, at one time or another, to belong to the Pachycephalidae, or to be close to it.

The aims of the study are then mentioned: to identify the nature of the toxicity, whether it is basal or derived independently; to evaluate the evolution of bright coloration in link with toxicity; and to verify the monophyly of Pitohui to test for mimicry.

55 specimens from various museums around the world were analysed in this study. The authors used standard procedures used in molecular systematics to gather the DNA from the specimens, then sequence and align the genes. The necessary phylogenetic reconstruction was then carried out using specialised software, including such techniques as Bayesian analysis (a way of modelling the likelihood of the evolution of the genes). A single maximum-likelihood tree was produced as the output, which looks very interesting.

It is evident from this tree that the pitohuis are not monophyletic, but polyphyletic. Pitohui dichrous and P. kirhocephalus form a monophyletic clade, “P.” ferrugineus and “P.” incertus seem to belong with the shrike-thrushes (Colluricincla spp.), “P.” tenebrosus, endemic to the Pacific island of Palau, is nested very neatly within Pachycephalus, the whistlers, with “P.” nigrescens as another member of this group, and “P.” cristatus fits in at the outside of this large group. Other monotypic genera of the Pachycephalidae are outside this group, with only the expected outgroups outside this. The ifrita, by the way, pairs with the greater melampitta, close to the outgroup of the birds-of-paradise.

So, what to make of this? The discussion section of the paper starts by mentioning other generic names given to some of the members of the genus “Pitohui”. The authors then admit to the polyphyly of the genus, and that they will present the results of this elsewhere in the future. I predict that P. dichrous and P. kirhocephalus will stay as they are, but the other species will have to be placed in different genera.

It is no coincidence, then, that the two species of pitohui that do form a true clade are the most vividly coloured, and the most toxic. P. kirhocephalus, the variable pitohui, is so called because of the variety of plumage forms, some brighter than others; the analysis seemed to support the monophyly of the different subspecies of P. kirhocephalus, but the data may not have been strong enough, as some of the specimens were “ancient”.

The fact remains, however, that the other birds known as pitohuis, not to mention the ifrita, are also toxic; could any other birds in the group also be toxic? Of those birds, only one, the little shrike-thrush, Colluricincla megarhyncha, tested positive, but only slightly, and perhaps the other members of that genus. Natives of New Guinea were surveyed to further test this idea, but no additional toxic birds were identified. The authors then state that, from their studies, it is likely that toxicity evolved multiple times within the Corvoidea, and it is not a basal trait. It is also likely that the pitohuis are not affected by the toxins in their beetle prey; instead, they sequester it and modify it for their own use.

The similarity of P. dichrous and P. kirhocephalus to the monarch butterfly is noted, being an example of aposematic coloration, where colours and patterns serve as a warning to potential predators. This idea was mentioned in their introduction, but they go into some more detail in their discussion. It appears that there is no clear link between coloration and toxicity, as many of the duller birds are toxic, and many of the brightly coloured ones (male birds-of-paradise included) are not. Sexual selection is cited as another possible reason for the coloration, however, this fails for the same reasons as above.

The polyphyletic pitohuis have many common characteristics; firstly, most possess some degree of toxicity while their relatives do not; secondly, they participate in mixed-species flocks and are noisy and gregarious birds, their sister taxa notably being quite contrary in this way; thirdly, they outwardly appear to be morphologically similar, whilst apparently being unrelated. Convergence is apparent in not just toxicity then, but appearance, behaviour and ecology too!

The authors admit the speculations about Batesian or Müllerian mimicry need more testing, but that there is a definite presence of some sort of mimicry, otherwise unknown amongst birds.

They conclude by mentioning the status of the morningbird, “P.” tenebrosa from Palau, putting its remarkable external difference from the Pachycephalus genus it now belongs to down to increased rate of evolution from being on a remote island.

Dumbacher, J. P., K. Deiner, L. Thompson, & R. C. Fleischer (2008). Phylogeny of the avian genus Pitohui and the evolution of toxicity in birds. Molecular Phylogenetics and Evolution 49:774-81.

Saturday 10 January 2009

Photo of the Day #25: White-winged Wood Duck

Keep your entries coming in for Cranial Challenge, please; nobody who has entered has yet got them all right!! I will close the competition at the end of the month, until then, give us your best guess at the 26 vertebrate skulls, or those you know! You don't have to be specific; the full answers will be revealed in due course.

In the mean time, here's a photo of a White-winged Wood Duck I took at the London Wetland Centre on the penultimate day of 2008. It was bloody cold, but was otherwise a pleasant day, with teals and snipe giving me a nice show; overall a ruddy good way to end a year full of birdwatching, reptile-searching and fossil foraging!

White-winged wood duck
Cairina scutulata (Müller, 1842)
Anatidae; Anseriformes; Aves; Chordata
London Wetland Centre
December 2008

The white-winged wood duck is mostly believed to be a close relative of the ubiquitous Muscovy duck (the only commonly domesticated duck species other than the mallard), hence the placement in the genus Cairina, but this may be wrong, as molecular evidence has suggested. It looks like a Muscovy duck, so I'll leave it where it is for the time being; I distrust DNA highly. It's an endangered species from south-east Asia, held in an enclosure known as "Tropical Wetlands" in the London Wetland Centre; the only thing that looks vaguely tropical about that part is a plastic Rafflesia that pigeons seem to like sitting (and crapping) on. There were white-winged wood ducks there when I first started visiting the Centre in 2005, then they vanished, being replaced by Comb ducks Sarkidiornis melanotos (indeed found in tropical Asia, but the Centre holds the South American subspecies, S. m. sylvicola). Last month I found the white-winged wood ducks back, and in greater numbers.

Friday 2 January 2009

Caption Contest winners & Cranial Challenge

Congratulations to Traumador the Tyrannosaur who has won the caption competition from last month, featuring Darren Naish and Dave Martill!

"The itsy bittsy spider crawled up the cliff face, down came a wave and washed the spider out"

Traumador, you have won a personalised A3-sized illustration of the tetrapod or tetrapods of your choice! I would also like to offer the same prize to the stars of the photo.

The next competition has the same prize (it's all I can offer!), but is arguably more difficult. I have named it "Cranial Challenge", as it's all about identifying vertebrate skulls! There are 26 questions in the quiz, in alphabetical order from A to Z. If you think the answer for "A" is an American alligator (it isn't, by the way), then you can either just submit "alligator", or be more specific if you want. Most of the answers are the common name of the animal, but a few are of the scientific name. Send your answers to me by e-mail (see profile for e-mail address).



























Good luck!