Wildfowl Extinctions
© IUCN
This is a guest article, kindly contributed by Dr. Glyn Young, a conservation biologist at the Durrell Wildlife Conservation Trust in Jersey and chair of The IUCN Species Survival Commission Threatened Waterfowl Specialist Group. Dr. Young has long been interested in the world’s wildfowl and has travelled widely in search of them in distant places including Alaska, Argentina, Assam, Galápagos, Iceland, New Zealand, South Africa and especially Madagascar, which he has visited many times since 1989. Dr. Young has attained a master’s degree and PhD with studies on the ecology of Madagascar’s endemic ducks.
Wildfowl (Anatidae: ducks, geese and swans) are one of the most widespread groups of birds on the planet. High levels of dispersal and long-distance migrations have helped them reach almost every corner of the globe and, notably, every oceanic island, however remote. Like some other bird groups, particularly rails and pigeons, adaption to island life, in islands free from terrestrial mammals, has helped numerous very localised, endemic, species evolve. Unsurprisingly too, several species over time became flightless with other selective pressures leading to both gigantism and miniaturisation depending on available resources. Highly localised, small populations of flightless and edible birds. What could possibly go wrong?
As we humans explored the world, the oceans were no barrier to our dispersal too. Wherever we went we found birds to eat, birds that might have almost welcomed us. And if the arriving seafarers didn’t eat them themselves, their accompanying mammal travellers did, be they deliberate passengers like cats, dogs and pigs or uninvited ones like rats and mice. Naive, almost welcoming birds were no match for the colonisers.
Science has disappointingly often documented island wildfowl extinctions only since European explorers ‘discovered’ the world and wrote down and drew the wildlife they found. Of New Zealand’s large wildfowl diversity, only one has become extinct since Europeans arrived in 1642, and none of Hawaii’s once remarkable species have died out since James Cook visited first in 1778. Understanding the years between the first human contact and the first European visitors tells a much starker story.
The exact causes of a species’ extinction, however, can typically only be guessed at. The majority of wildfowl that have disappeared since first human contact were never documented and are only known from sub-fossil remains, often in middens that tell us just that they met the colonisers. That humans were involved in extinction in some way seems obvious but just how may not be clear. Of the most recent extinctions like the Labrador Duck Camptorhynchus labradorius (last bird shot in 1875) and Auckland Island Merganser Mergus australis (last two birds collected for museums in 1902) we may know how the species finally succumbed, but even then we have little idea on how they became so rare and localised in the first place. Was it exploitation like hunting and egg harvesting, widespread habitat modification or the impact of the many alien species that came with or followed the humans and outcompeted with waterfowl, spread disease, killed them or robbed their nests? Most likely it was a combination of some or all of these. It is unlikely that we ever will know exactly what killed off the species below, but that they met the human colonisers tells us a lot.
The Madagascar Pochard Aythya innotata was described as common at Lake Alaotra, Madagascar (until 2006 it’s only documented population) in the 1920s. It has since disappeared from Alaotra but we can still only surmise just why. There has been massive habitat modification and loss of wetlands in Madagascar for centuries but the sudden decline of the pochard follows the arrival of exotic fishes. But, whether the fish outcompeted them, increased turbidity and hindered the ducks from finding food, altered the habitat further or drew in more human pressures is unclear. Or indeed whether it really was the fish! This diving duck was rediscovered in 2006 and is, fortuitously, responding to conservation measures dedicated to its continuing survival.
Figure 1. The Madagascar Pochard (aythya innotata)
Terms of use: This image is licensed under a Creative Commons Attribution 2.0 Generic. It is attributed to Frank Vassen. The image is unedited and the original can be found here
Hawaii
Wildfowl evolution seems to have gone a bit crazy in Hawaii with some of the biggest species known. And some pretty weird ones. Hawaii was first colonised by humans around 1700 years ago. Of 10 known species, seven have gone extinct:
Giant Hawaiian Goose - Branta rhuax
Greater Hawaiian Goose (Nene-nui) - Branta hylobadistes
Kaua’I Turtle-jawed Moa-nalo - Chelychelynechen quassus
Stumbling (Short-billed) Moa-nalo - Ptaiochen pau
Maui Nui (Large-billed) Moa-nalo - Thambetochen chauliodus
O’ahu Moa-nalo - Thambetochen xanion
Kaua’I Mole Duck - Talpanas lippa
New Zealand
In New Zealand, the first human settlers arrived around 800 years ago, finding a large bird fauna that included flightless parrots, rails, songbirds and ducks, geese and swans as well as many species of moas and kiwis. These islands have lost 11 of around 18 endemic wildfowl species with the most recent, the world’s most southerly merganser Mergus australis, dying out by 1910:
North Island Goose - Cnemiornis gracilis
South Island Goose - Cnemiornis calcitrans
New Zealand Swan - Cygnus sumnerensis
Scarlett’s Duck - Malacorhynchus scarletti
Finch’s Duck - Chenonetta finschi
Chatham Island Duck - Anas (Pachyanas) chathamica
Auckland Islands Merganser - Mergus australis
Chatham Islands Merganser - Mergus milleneri
New Zealand Blue-billed Duck - Oxyura vantetsi
New Zealand Musk Duck - Biziura delautouri
Chatham Island Teal - Anas chlorotis ssp. Nov
Figure 2. An artists interpretation of the Kaua’I Turtle-jawed Moa-nalo (Chelychelynechen quassus)
Terms of use: This image is licensed under a Creative Commons Attribution 3.0 Unported. It is attributed to Stanton F. Fink. The image is unedited and the original can be found here
Indian Ocean
Madagascar and the Mascarene Islands in the western Indian Ocean have also not gone unscathed. Madagascar, an island continent with a guild of mammal predators, colonised by humans from possibly 2,000 years ago has lost two sheldgeese although it’s unclear why, while extinction of endemic wildfowl in the Mascarenes, colonised from the 16th century and home of the Dodo Raphus cucullatus and the solitaire Pezophaps solitaria, shouldn’t be too much of a surprise:
Lesser Madagascar - Sheldgoose Alopochen sirabensis - Madagascar
Mauritian Shelduck - Alopochen mauritiana - Mascarene Islands
Réunion Shelduck - Alopochen kervazoi - Mascarene Islands
Madagascar Sheldgoose - Centrornis majori - Madagascar
Mauritian Duck - Anas theodori - Mascarene Islands
Elsewhere in the Indian Ocean, the island of Amsterdam had lost an endemic, flightless dabbling duck, a species that succumbed to visiting sealers. A population on neighbouring St Paul May have been a further distinct species:
Amsterdam Island Duck - Anas marecula - Indian Ocean
Pacific
Populations have been lost from the Pacific islands too:
Coue's Gadwall - Mareca strepera couesi
Mariana Mallard - Anas platyrhynchos oustaleti
Rennell Island Grey Teal - Anas gracilis remissa
Continents
Continental areas have fared much better overall as wildfowl had other mammals to contend with before we came along, but extinctions have still been recorded. Extinctions of two flightless seaducks Chendytes on the North American west coast are not fully explained but it seems likely than humans spreading through the continent had some involvement. People were definitely involved in the more recent extinction of the Labrador Duck and, in Asia, two species, Pink-headed Duck Rhodonessa caryophyllacea and Crested Shelduck Tadorna cristata, have not been seen for many years but we never give up hope (the Madagascar Pochard was rediscovered in 2006):
Chendytes lawi - North America
Chendytes milleri - North America
Labrador Duck - Camptorhynchus labradorius - North America
Crested Shelduck - Tadorna cristata - Russia, Japan and South Korea. Last acceptable record 1964
Pink-headed Duck - Rhodonessa caryophyllacea - India, Bangladesh and Myanmar. Last acceptable record 1949.
I’d like to think that we’ve seen the last of wildfowl extinctions but sadly too many species are threatened with joining the others including some of the few remaining island species like New Zealand’s brown teals, two are flightless, Laysan’s diminutive mallard, Kerguelen, Crozet and South Georgia’s pintails and the Andaman and Sunda teals. The IUCN Threatened Waterfowl Specialist Group is committed to working to ensure that the world’s threatened and extinct wildfowl are better understood.
Figure 3. Preserved specimen of the Pink-Headed Duck (Rhodonessa caryophyllacea) from the Naturalis Biodiversity Center in Leiden.
Terms of use: This image is licensed under a Creative Commons Attribution-Share Alike 3.0 Unported. It is attributed to Huub Veldhuijzen van Zanten/Naturalis Biodiversity Center. The image is unedited.
Sources and Further Reading
New Zealand birds extinct since human contact
Hume, J. 2017. Extinct Birds. 2nd Edition. Bloomsbury Natural History
Walther, M. & Hume, J.P. 2016. The extinct birds of Hawaii. Mutual Publishing
Young, H.G., Razafindrajao, F. & Lewis, R.E. 2013. Madagascar’s wildfowl (Anatidae) in the new millennium. Wildfowl 63: 5–23. Link
Young, H.G., Tonge, S.J. & Hume J.P. 1997. Review of Holocene wildfowl extinctions. Wildfowl 47: 167-180. Link
Young, H.G. & Kear, J. 2006. The rise and fall of wildfowl of the western Indian Ocean and Australasia. Bulletin British Ornithologists’ Club 126A: 25-39. Link