Laysan Ducks: Not as Degenerate as People Used to Think

I really like ducks, and my god there’s a lot to say about them. Here, we look at a small Hawaiian duck that once stood on the very precipice of extinction, some sources saying that it was reduced to a single individual at one point. I speak, of course, of the famous Laysan duck Anas laysanensis…

Caption: to date, I’ve seen a single Laysan duck, and here it is. It was on show at WWT London Wetland Centre. The large amount of speckled white on the head and neck is typical of the species today but perhaps was not as prevalent in the past. The wing mirror isn’t obviously green in this individual, so I think this is a female. Image: Darren Naish.

It’s sometimes called the Laysan teal or Laysan mallard, though both names are less popular. When discovered by Europeans, the species was considered endemic to tiny Laysan Island – 3 km long and 1.5 km wide – and to its westerly and even smaller neighbour Lisianski (1.9 km long and 1 km wide), both in the Hawaiian Islands. Here, the species is mostly associated with brackish lagoons, though it does occur on the coasts (albeit not on the sea) and inland as well. As we’ll see, Laysan and Lisianski both served as a stopover for people on occasion but were otherwise uninhabited prior to their exploitation during the early 1900s. It’s surely this that enabled the duck to persist to modern times.

Caption: Laysan duck female and ducklings. Laysan ducklings have an appearance typical of mallards and kin, but their facial striping is less defined and prominent than that of mallards and African ducks (and Meller’s duck!); their body spots are more diffuse than those of mallards and most other related species. Image: Jimmy Breeden, public domain (original here).

Laysan and Lisianski were both (so far as we know) first visited by European in the 1820s, and an 1828 report by C. Isenbeck, the surgeon of the Russian ship Moller, made reference to birds on both islands (Moulton & Weller 1984). In the June of 1891, the islands were visited by Henry Palmer and George Munro on an expedition funded by Walter Rothschild, and this is when the first Laysan ducks (one male and one female at least) were collected, these ultimately being the type specimens named (in a very brief, half-page anatomical description) by Rothschild in the following year (Rothschild 1892). By 1891, the ducks were not findable on Lisianski.

Caption: the entire thing – the whole published work – that constitutes Walter Rothschild’s 1892 description and naming of the Laysan duck, from Bulletin of the British Ornithologists’ Club volume 1.

What Laysan ducks are like. A few things make the Laysan duck distinct. It’s small (35-40 cm long), brownish and heavily mottled, has white patches round its eyes, and orange legs. Given that the world population descends from a tiny relict population (read on for the story there), it’s worth saying that the appearance of the birds today might exhibit less variation than they did in happier times*. The sexes are similar but females are browner and a bit smaller than males. When positioned alongside other members of the mallard group, Laysan ducks are obviously small, and also shorter-legged and shorter-winged, with shorter primaries.

* Alexander Wetmore – observing the birds in 1923 – noted that “traces of albinism” were present in the small number of birds existing at that time. I wonder if the white markings that are now a standard feature of the species were originally rare and have only become fixed due to founder effect.

Caption: plate from Delacour (1956) featuring the Laysan duck (at lower left; male and female) and other members of the mallard clade, art by Peter Scott. A Koloa or Hawaiian duck pair are to the right.

A number of behavioural observations were gathered and summarised by Jean Delacour in his 1956 The Waterfowl of the World. Laysan ducks can fly but prefer not to, and when approached by people they don’t fly far (though read on). In fact, people who’ve described their wild behaviour note how relatively unafraid of humans they are, which is of course typical for island-endemic animals. Palmer described the birds as “exceedingly tame” (Delacour 1956, p. 50). Like all ducks, they’re flightless during the time of wing moult (usually July and August).

Caption: Laysan ducks with brine fly swarms, though not obviously feeding on them. Image: Dr James P. McVey, NOAA Sea Grant Program, public domain (original here).

Laysan ducks are flexible in dietary terms, feeding aquatically on algae, seeds and invertebrates, and foraging on land for the terrestrial equivalents of these things (Moulton & Weller 1984, Reynolds et al. 2006). They’re one of several birds known to run through waterside swarms of brine flies with an open mouth in an effort to grab as many flies as possible. In fact, brine flies appear to be one of the most important of their food items, especially during relatively wet years (Reynolds et al. 2006).

Caption: additional images of the lone Laysan duck I’ve seen, on show at the WWT London Wetland Centre and photographed in 2014. Images: Darren Naish.

Discovery and evolution. As we’ve seen, the Laysan duck was first scientifically named as a distinct species. It does look ‘distinct enough’ to warrant species-specific status, and this is the view we support today. However, for much of the 20th century it was widely thought that any dabbling duck taxon that looked even vaguely mallard-like – especially those of restricted distributed – was most sensibly regarded as a mallard subspecies, in effect one that had adopted a sedentary lifestyle. One consequence of this is that Laysan duck is entirely absent from some otherwise very comprehensive books on wildfowl… looking at you, Oscar Merne’s 1974 Ducks, Geese and Swans and Eric Soothill and Peter Whitehead’s 1978 Wildfowl of the World.

Caption: the mallard is an extraordinarily successful bird with a massive (albeit almost entirely Northern Hemisphere) distribution that involves tropical Asia, northern Africa, the Neotropics and the Arctic Circle in addition to the temperate places we mostly associate it with. As expected, its phylogenetic structure is complex and it has hybridised with several other dabbling duck species. The birds here were all photographed in England but for the one at lower right, which was in Portugal. Images: Darren Naish.

And another consequence concerns how the bird became ‘framed’. Delacour (1956, p. 49) described the Laysan duck as “undersized, inbred” which shows how there was often the implication that these supposed mallard variants were somehow… degenerate. Such views aren’t just relevant to the way animals are listed in books but also have a real-world effect, since they shape interest (or lack of) among biologists and conservationists, lead to apathy among politicians and popular writers, and ultimately shape conservation strategies (or their absence).

As it turns out, the ‘degenerate hypothesis’ was both undertested and based on unjustified assumptions, and the more we’ve learnt about the ducks in question the more obvious it’s become that they’re not just distinct; they also occupy important positions in phylogeny. Meller’s duck A. melleri, for example, was also long regarded as a ‘degenerate’ mallard variant but has turned out to be a critical early-diverging member of the entire mallard clade (Johnson & Sorenson 1999).

Caption: Meller’s ducks I’ve encountered in captivity, in Bristol Zoo (at left) and the Isle of Wight Zoo. This bird might look superficially like a mallard, but it’s also obviously distinct in plumage and proportions, an observation consistent with molecular data and phylogenetic studies. Meller’s duck was covered at Tetrapod Zoology back in 2009. Images: Darren Naish.

As an aside, there are a number of interesting reasons why the ‘degenerate hypothesis’ (this is my term, by the way, not one in general use) was developed in the first place; we owe much of it to claims made by Konrad Lorenz in the 1940s, and by what Paul Johnsgard said afterwards (Young & Rhymer 1998). It turns out that the underpinning claims and observations they reported on mallard-like ducks were faulty and erroneous (Young & Rhymer 1998). Wildfowl expert Glyn Young gave an excellent talk on this subject at TetZooCon 2018.

Caption: Johnson & Sorenson’s dabbling duck phylogeny of 1999. Laysan ducks (A. laysanensis) are shown here as being part of a polytomy that also includes a Philippine duck + ‘mallard 1’ clade and an American black duck + ‘mallard 2’ clade. This is Johnson & Sorenson’s strict consensus tree; other trees they show have a tidier topology in the mallard clade. Image: Johnson & Sorenson (1999).

DNA tests performed on Laysan ducks in the 1990s finally established that they were not ‘degenerate’ mallards after all, but a distinct lineage that descend from East Asian dabbling ducks that were themselves close to the ancestry of the Pacific black duck A. superciliosa, Philippine duck A. luzonica, and the spot-billed ducks and mallards proper (Cooper et al. 1996, Johnson & Sorenson 1999). This also overturns the suggestion that the Laysan duck might descend from the especially mallard-like Hawaiian duck or Koloa A. wyvilliana…. if anything, things are the other way round, since it now appears that the Koloa originated from Late Pleistocene or Holocene hybridisation between Laysan ducks and mallards (Lavretski et al. 2015).

Caption: Cooper et al.’s 1996 molecular phylogeny, showing grouping of Koloa with mallard, and of fossil (I’m not a fan of the term ‘subfossil’, it’s redundant) ducks of the main islands with living Laysan ducks. Image: Cooper et al. (1996).

This hybrid origin for the Koloa is consistent with the fossil record, since it shows Laysan ducks alone occurring on the Hawaiian Islands in the middle Pleistocene, the existence of forms intermediate between Laysan ducks and Koloa in the Holocene, and the presence of Koloa proper in recent deposits only (Cooper et al. 1996, Lavretski et al. 2015).

Caption: the Hawaiian Islands, with Laysan and Lasianski visible in the ‘middle’ of the northwestern island. Image in the public domain, original here.

Fossils also show that Laysan ducks are only associated with Laysan (and Lisianski) due to regional extinction. Prior to human hunting, they occurred across the Hawaiian Islands. Laysan and Lisianski are over in the west (being among the Northwestern or Leeward Islands), but Holocene Laysan duck fossils are known from most of the big or main islands over in the east (the Southeastern or Windward Islands), namely (from west to east) Kauai, Oahu, Molokai, Maui and Hawaii (Cooper et al. 1996, Burney et al. 2001). Other islands are between Laysan and Kauai, so the ducks presumably occurred on those too.

Caption: captive (probable female) Laysan duck at WWT London Wetland Centre. Image: Darren Naish.

Reduction and near-extinction. As is typical for island-dwelling wildfowl, the Laysan duck has not fared well in interaction with people, as is demonstrated by its modern restriction to Laysan. Laysan was occupied by guano miners during the late 1800s, and their hunting of the duck reduced its numbers substantially, such that less than 100 were findable by the early 1900s. The relict Lisianski population was killed off between the 1820s and 90s.

The guano miners also introduced rabbits to Laysan, not for food but because the former manager of the guano company planned to start a rabbit-meat industry. The rabbits had increased massively in numbers by 1911, their behaviour reducing vegetation and causing inland drifting of sand. Japanese plumage hunters (there to collect albatrosses) arrived on Laysan in 1909 and hunted the ducks for food, and only six birds could be located in 1912 (Delacour 1956). Attempts to eradicate the rabbits had occurred by 1919.

And then along came Alexander Wetmore. Wetmore (1886-1978) was and is a respected and well celebrated American ornithologist, associated with the Smithsonian Institution, who published a good number of influential studies on birds living and extinct. He led field expeditions across the Pacific and contributed to the running and direction of several bodies, including the National Geographic Society and the Society for Science and the Public. In 1923, Wetmore visited Laysan and found 20 surviving ducks. He collected six, some of which “were so lacking in power of flight that they were exhausted after going 125 yards. He easily ran them down and captured some by hand” (Delacour 1956, p. 50). As a trained scientist, I appreciate and understand the value and role of what we call biological collecting (and yes, we’re not pretending that this is anything other than the killing and taking of living things). But killing six of a group of 20… of what is effectively a species clinging to the brink of existence… never sits right with me. You might disagree.

Caption: a consequence of the Laysan’s ducks’ closeness to extinction is that it’s featured in numerous books on endangered and near-extinct animals, in this case the Brooke Bond Picture Cards Wildlife in Danger of 1963, written and illustrated by Peter Scott.

Caption: here’s Peter Scott’s Laysan duck tea card painting in close-up. As a wildfowl expert, aficionado and conservationist and an artist, he painted this species on several occasions during his life. Peter Scott has been written about before at Tetrapod Zoology, most recently because of his involvement in Loch Ness Monster research and popularisation.

Conservation and a sort of recovery. What happened next? A few sources state that the species was reduced to but a single wild individual by 1930, a pregnant female who (obviously) laid a fertile clutch (Halliday 1978). Whether that’s true or not, the ducks did increase in numbers after this, such that 33 were found in 1950, nine of which were captured and taken to Honolulu Zoo in Oahu for a captive breeding programme in 1957.

Another 36 ducks were captured and transported in 1958. Birds from this captive stock were then transported to facilities around the world, including San Diego Zoo and Slimbridge in the UK (Reynolds & Kozar 2000), and about 500 were in existence in 1987. At the time of a 2000 review, 32 facilities around the world housed Laysan ducks and they’d proved easy to breed in captivity, though inbreeding depression remained a concern (Reynolds & Kozar 2000).

Caption: more Laysan duck appearances in books on endangered wildlife. The image at left (illustration by Darryl Wheye) is from Paul Ehrlich et al.’s 1992 Birds in Jeopardy: the Imperiled and Extinct Birds of the United States and Canada, Including Hawaii and Puerto Rico; that at right is from Halliday’s 1978 Vanished Birds (all illustrations in the book are by Halliday himself).

The Laysan duck is currently a CITES Appendix I species and numerous efforts have been made to restore and renovate its habitat on Laysan. These have been sufficiently successful that Laysan was considered close to carrying capacity (or maximum duckage, to use the technical term*) by the early 2000s, and groups were then translocated to Midway Atoll in 2004-2005 and the Kure or Lisianki Islands in 2014.

* Not actually a technical term.

This is a great conservation success story, but never forget that it’s due to a lot of work, both administrative and practical. And things aren’t entirely in the clear since a die-off due to drought in 1993, outbreaks of avian botulism in 2008 (and since) and damage caused by storms and a tsunami in 2011 continue to cause issues for the birds. A very detailed, comprehensive review of the Laysan duck’s conservation status and history can be found here at BirdLife International.

Caption: a Laysan duck group photographed in the wild on Laysan. Despite statements that Laysan ducks don’t enter the sea, this image seems to show the birds in coastal waters… though it could be a lagoon or lake. Image: Forest and Kim Starr, CC BY 3.0, original here.

Boring ducks aren’t so boring. The story of this small, obscure, seemingly boring little brown duck proves – I think – to be quite interesting. Fossils and molecular data have painted a picture of the duck’s history and distribution quite different from what was originally thought to be true; the species fits into a larger debate on mallard-like ducks and how they should be interpreted; and – finally – the Laysan duck really has to be considered quite the posterchild when it comes to management, captive breeding and escaping the edge of extinction.

Don’t worry; more ducks soon…

For previous Tetrapod Zoology articles on duck and other wildfowl/waterfowl, see…

Tetrapod Zoology is an independent blog. I can devote more time to it and produce more content the more support I receive. Support me at patreon and you also get to see the more than 550 in-prep illustrations being produced for my various projects.

Refs - -

Burney, D. A., James, H. F., Burney, L. P., Olson, S. L., Kikuchi, W., Wagner, W. L., Burney, M., McCloskey, D., Kikuchi, D., Grady, F. V., Gage, R. & Nishek, R. 2001. Fossil evidence for a diverse biota from Kaua'I and its transformation since human arrival. Ecological Monographs 71, 615-641.

Cooper, A., Rhymer, J., James, H. F., Olson, S. L., McIntosh, C. E., Sorenson, M. D. & Fleischer, R. C. 1996. Ancient DNA and island endemics. Nature 381, 484.

Delacour, J. 1956. The Waterfowl of the World, Volume 2: The Dabbling Ducks. Country Life Ltd, London.

Halliday, T. 1978. Vanishing Birds: Their Natural History and Conservation. Holt, Rineheart and Winston, New York.

Johnson, K. P. & Sorenson, M. D. 1999. Phylogeny and biogeography of dabbling ducks (genus: Anas): a comparison of molecular and morphological evidence. The Auk 116, 792-805.

Lavretsky, P., Engilis, A., Eadie, J. M. & Peters, J. L. 2015. Genetic admixture supports an ancient hybrid origin of the endangered Hawaiian duck. Journal of Evolutionary Biology 28, 1005-1015.

Moulton, D. W. & Weller, M. W. 1984. Biology and conservation of the Laysan duck (Anas laysanensis). The Condor 86, 105-117.

Reynolds, M. H. & Kozar, K. 2000. History and current status of the Laysan duck (Anas laysanensis) in captivity. ‘Elepaio 60 (4), 59-65.

Reynolds, M. H., Slotterback, J. W. & Walters, J. R. 2006. Diet composition and terrestrial prey selection of the Laysan Teal on Laysan Island. Atoll Research Bulletin 543, 181-199.

Rothschild, W. 1892. Anas laysanensis. Bulletin of the British Ornithologists’ Club 1, 17.

Young, H. G. & Rhymer, J. M. 1998. Meller’s duck: a threatened species receives recognition at last. Biodiversity and Conservation 7, 1313-1323.