The Madagascar pochard returns
Anyway, so by now the cat is out of the bag, and the news isn’t news anymore anyway: the
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
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
Following the pochard’s decline, thorough searches failed to reveal any trace of its continued presence. However, a publicity campaign amongst villages around
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).
As an extinct species, the
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
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.
[adjacent photo, showing two male Madagascar pochard, by Lily-Arison Rene de Roland]
So, as announced on
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
Mourer-Chauviré, C., Bour, R., Ribes, S. & Moutou, F. 1999. The avifauna of
Young, H. G. & Kear, J. 2006. The rise and fall of wildfowl of the western
- . & Smith, J. G. 1989. The search for the
- ., Tonge, & Hume, J. P. 1996 Review of Holocene wildfowl extinctions. Wildfowl 47, 166-180.