The Madagascar pochard returns

This post would have been up a long time ago if I hadn’t had to spent the last week grubbing around for money, and on that subject… the more observant among you might have noticed a paypal donate button just beneath my biography. It never occurred to me that if I ask for money I might get it, but thanks to a very generous blog reader I have learnt that there are, to my astonishment, people prepared to do just this. So if you have spare money kicking around and feel like making my life easier…

Anyway, so by now the cat is out of the bag, and the news isn’t news anymore anyway: the Madagascar pochard Aythya innotata, supposed extinct since 1992 (when the ‘last’ specimen died in captivity), has been rediscovered. Ducks are another of those tetrapod groups that we take for granted and regard as mundane, yet they’re actually a-maz-ing. Before getting into pochards into any detail, let’s remind ourselves how amazing ducks are.

Ducks are amazing

At least some ducks have particularly interesting sex lives, involving over-sized sex organs, gang rape and occasional necrophilia. Some species are bizarrely aggressive*, regularly attacking and beating other waterbirds to death. Some ducks can carry their eggs and/or their juveniles in flight, and some species practise nest parasitism. Herbivory, filter-feeding, carrion-feeding and flightlessness have all been evolved by ducks. Many duck species are amazingly mobile, and consequently have enormous global ranges (an issue which is particularly significant with regard to mallards Anas platyrhynchos and their close relatives and derivatives: a subject I aim to cover at another time). Their mobility is particularly interesting for two reasons. Firstly, it means that they are particularly good at colonising remote islands, and because populations have repeatedly become sedentary after having made a colonisation, ducks have also been good at evolving island endemics. Secondly, it means that ducks excel in transporting things, such as sediment particles and small or microscopic organisms.

* Notably steamer ducks: go here for more.

Ducks – particularly herbivorous species such as pochards – have proven to be highly important transporters of aquatic plants, both as seeds stuck to their feathers or feet (a form of transport known as epizoochory), and as propagules carried in the bird’s gut (a form of transport known as endozoochory). Ostracods and small snails also get transported by ducks, in cases for distances of 30 km or so. The mobility of ducks (and other wildfowl) also has implications for the spread of viruses: recent work indicates that naturally migrating wildfowl were responsible for spreading the HPAI H5N1 virus from Russia and Kazakhstan to eastern Europe (Gilbert et al. 2006).

Anyway, back to pochards. Sometimes called bay ducks, pochards – the tribe Aythyini – are one of four clades that together make up Anatinae, the true duck group (the other anatine clades are Malacorhynchini [pink-eared ducks], Anatini [surface-feeding ducks] and Mergini [seaducks]). Found virtually worldwide, the 17 pochard species are diving ducks with high wing loadings and several specialisations for subaqueous locomotion. Some species do a distinctive leap before diving, and some have to run across the water surface before taking off (others are more typical in being able to leap directly from the water’s surface). Pochards are mostly migratory, breed near permanent bodies of freshwater, and, except three of the scaups, all are predominantly herbivorous.

The sad ‘loss’ of the Madagascar pochard

So back to the latest news from the world of pochards: the amazing rediscovery of the Madagascar pochard, also known as the Madagascar white-eye. First described from Lake Alaotra in central-eastern Madagascar in 1894, it was apparently still common during the 1930s and is even said to have been still common in Soothill & Whitehead’s 1978 Wildfowl of the World. This was incorrect however, as in fact the species hadn’t been found at the lake since 1971 (Young & Kear 2006), and the last published sighting comes from 1970. Furthermore, the 1970 sighting is controversial: it described an observation of the pochard at Lake Ambohibao (near Antananarivo), and as such is (so far as I can tell from the literature) the only sighting made away from Lake Alaotra. Incidentally, pochard bones from Reunion may or may not be anything to do with the Madagascar pochard (Mourer-Chauviré et al. 1999): if the Reunion bones are referable to this species, then it had a far wider range in the recent past than it did in the 19^th and 20^th centuries.

Following the pochard’s decline, thorough searches failed to reveal any trace of its continued presence. However, a publicity campaign amongst villages around Lake Alaotra in 1989 then led to the 1991 capture of a single male. He was kept in captivity, but died in 1992, and little about the biology and behaviour of the species was learnt from the individual. This is unfortunate as the Madagascar pochard is particularly poorly known, though given that its specific name means ‘unremarkable’, you might think that there isn’t much to know about it. We do know that, like other pochards, it feeds by diving, probably for the seeds of water-lilies and other plants and invertebrates.

The Madagascar pochard’s decline and apparent extinction seems predominantly to have resulted from extreme habitat degradation and the introduction of both herbivorous and carnivorous fish (including tilapia and large-mouth bass). Severe deforestation of the local hills has resulted in silting-up of the lake, the consequence of which has been the spread of papyrus marsh, the consequence of which has been the setting alight of the marshes to stop them spreading, the consequence of which has been the inadvertent killing of nesting birds. Carp (introduced in 1926), tilapia (introduced in 1955) and black bass (introduced in 1961) are among several alien fish that now live in Lake Alaotra. These fish appear to compete with native waterbirds by eating the same plants and invertebrates, and the larger, carnivorous fish species may predate upon pochard ducklings. Nylon monofilament gill-nets, hidden by local fishermen in open water or at the bases of aquatic plants, are thought to have seriously affected diving birds, including the pochard as well as grebes (Young & Smith 1989).

Given all these problems, it is not surprising that the pochard declined to apparent extinction. The Alaotra or Delacour’s grebe Tachybaptus rufolavatus [image above, at left], discovered in 1929 and described in 1932, is unique to the lake and also appears to have become extinct (partly due to hybridisation with the African little grebe T. ruficollis capensis). Lake Alaotra is also home to the Alaotra lemur Hapalemur griseus alaotrensis [image at left]: the only primate that spends most of its life in marshland. Confirming the presence or absence of any of these animals, particularly the pochard, is difficult however as ‘the marsh is so extensive and difficult to travel in that the duck could easily go undetected inside it’ (Young & Smith 1989, p. 23).

As an extinct species, the Madagascar pochard would join a long and sorry list of recently extinct wildfowl, many of which were endemic to small islands. Young et al. (1996) listed an amazing 54 wildfowl that have become extinct within the last 10,000 years. Most of these birds are obscure and familiar only to specialists, but a handful have been widely featured in the literature and are relatively familiar. Among the latter is the Pink-headed duck Rhodonessa caryophyllacea [image at left], a highly distinctive pochard of India and Bangladesh, named in 1790 and widely regarded as having gone extinct in the 1930s or 1940s. Given that the Pink-headed duck is – like the Madagascar pochard – a pochard, it bears discussing where it fits within this duck group. Luckily both morphological and molecular analyses have been published on this very issue.

Is Rhodonessa a Netta, or is Netta a Rhodonessa?

In a phylogenetic analysis of skeletal, integumentary and soft-tissue characters, Livezey (1996) concluded that the members of Aythyini fell into four major groups, which in branching order are: the stem or narrow-billed pochards, the redheads, the white-eyes, and the scaup. The Marbled duck Marmaronetta angustirostris was the most basal member of the clade, and also the smallest (at less than 500 g). Basal members of the clade are Palearctic in distribution, and it seems that a number of independent invasions of South America, Africa, Madagascar and Australasia occurred during the group’s history. The grouping of the Pink-headed duck as the sister-taxon of the Red-crested pochard Netta rufina (both species down at the base of Aythyini within the stem pochard clade) led Livezey to argue that the two should be regarded as congeneric. With Rhodonessa coined by Reichenbach in 1853 and Netta by Kaup in 1859, the former supposedly had priority, so the Red-crested pochard – a familiar species to anyone that knows ducks – became renamed Rhodonessa rufina (Livezey 1996) [adjacent image shows male Red-crested pochard].

However, Livezey had made a mistake, as Kaup named Netta in 1829, not 1859, so in later publications he switched things round, now sinking the Pink-headed duck into Netta, and hence renaming it Netta caryophyllacea (Livezey 1997). This hasn’t been widely accepted however. The Pink-headed duck and Red-crested pochard are hypothesised to be sister-taxa, and hence any decision about their generic status is down to opinion about how different, or similar, they are. Are they really similar enough to be lumped together in the same genus? No: they look markedly different, and hence most ornithologists have argued that there’s nothing wrong with retaining separate generic status for both of them.

It’s fairly well known that the Pink-headed duck was really strange. Really, really strange: go here for a higher-res version of the adjacent image. Chocolate brown except for a pink speculum, head and neck, it sported a remarkably strange and unique, long-necked, stiff-necked posture. A short, rounded occipital crest sat at the back of the head; its syringeal bulla was flattened, rather than rounded as in other pochards. Its white, spherical eggs lacked the ‘soapy’ texture characteristic of duck eggs, and its feet resembled those of dabbling ducks more than those of other pochards. Far less appreciated is that the Red-crested pochard is also odd, however, with more recognised autapomorphies than the Pink-headed duck. Features of its syringeal bulla are unique, it has that rounded, bushy head crest, and various details of the plumage on its flanks, wings and neck are unique. In view of all these profound differences it seems most appropriate to keep Rhodonessa and Netta as separate, even if they are more closely related to each other than to other pochards.

The Madagascar pochard returns

[adjacent photo, showing two male Madagascar pochard, by Lily-Arison Rene de Roland]

So, as announced on November 20^th 2006 by The Peregrine Fund – an international conservation group that focuses on raptor-based conservation efforts – the Madagascar pochard has now been officially rediscovered. It really was hiding out, and not extinct. National Director for The Peregrine Fund’s Madagascar Project, Lily-Arison Rene de Roland, and field biologist Thé Seing Sam, observed 13 Madagascar pochards in total, four of which were juveniles (for their photos, please go here). This is great news, as if the right conservation efforts are put in place the bird might be pulled back from the brink of extinction. It also provides hope for species that are possibly extinct, but are both highly cryptic and inhabit remote and difficult areas. Err, like the Pink-headed duck? Hmm, more on that another time.

For the latest news on Tetrapod Zoology do go here.

Refs - -

Gilbert, M, Xiao, X., Domenech, J. Lubroth, J., Martin, V. & Slingenbergh, J. 2006. Anatidae migration in the Western Palearctic and spread of highly pathogenic avian influenza H5N1 virus. Emerging Infectious Diseases 12, 1650-1656.

Livezey, B. C. 1996. A phylogenetic analysis of modern pochards (Anatidae: Aythyini). The Auk 113, 74-93.

- . 1997. A phylogenetic classification of waterfowl (Aves: Anseriformes), including selected fossil species. Annals of Carnegie Museum 66, 457-496.

Mourer-Chauviré, C., Bour, R., Ribes, S. & Moutou, F. 1999. The avifauna of Reunion Island (Mascarene Islands) at the time of the arrival of the first Europeans. Smithsonian Contributions to Paleobiology 89, 1-38.

Young, H. G. & Kear, J. 2006. The rise and fall of wildfowl of the western Indian Ocean and Australasia. Bulletin of the British Ornithologists’ Club 126, 25-39.

- . & Smith, J. G. 1989. The search for the Madagascar pochard Aythya innotata: survey of Lac Alaotra, Madagascar October-November, 1989. Dodo, Jersey Wildlife Preservation Trust 26, 17-34.

- ., Tonge, & Hume, J. P. 1996 Review of Holocene wildfowl extinctions. Wildfowl 47, 166-180.