Mystery birds of the Falkland Islands

In a previous post I discussed the little-known case of the Odedi, a cryptic passerine from Bougainville Island in the SW Pacific: it had been heard many times before a specimen was finally procured and the species was officially recognised. If that sort of thing interests you, you might then be pleased to learn that there are actually quite a few little crypto-birds of this sort, mostly unknown to all but specialists.

Unidentified owls on the Mascarenes, the Andaman and Nicobar islands; a black, long-tailed passerine, notable for its startling rattle-like call, from Goodenough Island in the D’Entrecastaeux Archipelago; mystery African gallinules and touracos; a Kenyan long-tailed passerine with reddish undertail-coverts; an all-black Kenyan swift (Ali & Ripley 1969, Williams & Arlott 1980, Beehler 1991, Shuker 1998). There are others that are even less well reported: a brown, thrush-sized duck from St. Paul Island in the Indian Ocean (described by John Barrow in 1793); an unverified serin from Ethiopia, referred to in passing by Clement et al. (1993, p. 17); and… the mystery birds of the Falkland Islands.

The Falkland Islands and their native fauna

Recently I’ve been reading Robin W. Wood’s Guide to Birds of the Falkland Islands. It’s not just a field guide: Wood (an outstanding field ornithologist and collector of data*) included stacks of information on Falkland ecology, topography, and ornithological history. Consisting of 780 islands (only two of which – East Falkland and West Falkland – can be considered large), the Falklands are located about 500 km northeast of continental South America. There are some really strange landscape features: the stone-runs for example, which are accumulations of large, angular boulders arranged on the sides of hills and valleys, and there are no native trees (though many trees have of course been planted by human colonists).

* And also a psychologist, metereologist and ecologist by the way.

Mostly the islands are covered by what’s known as oceanic heath: an association of rushes, sedges and mosses that grows on peat layers up to 13 m thick. Tussac grass (or tussock grass, depending on your preference), up to 3.5 m tall, forms dense stands in coastal areas and acts as an important nesting place for petrels, shearwaters, penguins and others. Tussuc is highly sensitive to grazing by large herbivores (introduced cattle all but eradicated it on the larger islands) and, worldwide, tussac species only occur where native herbivorous mammals are rare or absent. Whether the islands were glaciated or not during the Pleistocene remains controversial (McDowall 2005).

As you might expect, there are no lissamphibians or non-avian reptiles native to the islands. There was a native land mammal: the Warrah or Antarctic wolf Dusicyon australis, sadly hunted to extinction by 1876. Darwin, who encountered these canids in 1833, famously described how tame and trusting they were. A single bat – a vagrant from Patagonia - has been recorded, and there is also an unverified mention of a small mouse (Day 1981). The avifauna of the islands is pretty good though, with about 36 resident species and 18 additional species recorded as vagrants. The residents are mostly birds of moorland, freshwater environments and shores.

Avian extinctions on the Falklands

It is widely stated in the literature that King penguins Aptenodytes patagonicus were made extinct on the Falklands some time around 1870 by the destruction of the last rookery by a shepherd. Apparently he boiled down the birds to use their oil to waterproof a roof, though some authors have doubted the veracity of this story (Simpson 1976). King penguins were thereafter absent from the islands for a while, but by the 1940s they were breeding there and today there are several large colonies.

Less well known is that several birds reported to be present on the islands during the 19th century are no longer there, and hence are assumed to have become locally extinct. Darwin reported or collected Cinereous harriers Circus cinereus, Andean tapaculos Scytalopus magellanicus, Austral canasteros Thripophaga anthoides and Yellow-bridled finches Melanodera xanthrogramma, all apparently breeding residents. While the harriers were reported by Darwin to be tame residents, by the 1920s they were rare enough to become classified as accidental visitors, and only a handful of sightings have been recorded since the 1960s. The tapaculos haven’t been reported since the 1830s and Yellow-bridled finches haven’t been reported with confidence from the islands since 1916. The record of the canastero is problematical as Darwin never mentioned this species in Voyage of the Beagle, published in 1841, and later authors regarded Darwins’s ‘Falkland’ canasteros as having come from Chile. Maybe he mis-labelled the relevant specimens.

A Speckled crake, perhaps

Moving now to the birds for which specimens weren’t retained, Woods (1988) discussed the 1921 capture of a small rail on the bank of a stream near Stanley (the capital, on East Falkland), as reported by Bennett (1926). Was it a Speckled crake Coturnicops notata (sometimes called Darwin’s rail), as thought by Bennett? If so that’s pretty important because the Speckled crake is extremely rare and poorly known, with less than 20 specimens in museum collections. Bennett’s bird died but its skin wasn’t kept, and hence its identification was never verified. There don’t seem to be any other Speckled crake records from the Falklands, nor records of any other, similar rail.

The ‘mystery wrens’

There’s more. The Falklands also have a mystery wren, or at least a wren-like passerine. Reported several times since 1910, Wace (1921) listed records from Carcass and West Point Islands as well as other places. Woods (1988) discussed the descriptions of these birds that had been passed to him by K. Bertrand. A light eye-ring and russet plumage were mentioned, and while, overall, the birds seemed similar to juvenile House wrens Troglodytes aedon or Grass wrens Cistothorus platensis, Woods mentioned photographs taken in 1975 that seemed to show a longer tail than that present in House wrens. Further descriptions were provided by A. Douse following ‘mystery wren’ observations made in April 1987 at Pebble Island and Port Stephen, and Woods ended his discussion of these unidentified passerines by stating ‘Further careful observations are needed to identify these birds’ (1988, p. 225). Obviously, the most recent source I’ve consulted on this matter is Woods’ volume, and I’ve been unable to determine whether these birds have been identified since Woods published this book. Does anybody know?

If you’re wondering, the ‘mystery wrens’ are not the same thing as Cobb’s wren Troglodytes cobbi, a Falkland Island bird that’s only recently become recognised as a distinct species in its own right. Named in 1909, it was regarded as a subspecies of the House wren until Woods (1993) argued that it should warrant specific status, a decision since supported by others. As such it’s one of only two bird species endemic to the Falklands – the other is the Falkland steamer duck Tachyeres brachypterus (take note McDowall (2005), who listed Tachyeres brachypterus as the only endemic Falkland Island bird species). Ah yes, steamer ducks. Must blog about them one day.

Given their strong similarity to definite wrens, it’s almost certain that ‘mystery wrens’ really are wrens: that is, members of Troglodytidae. By the way (this is directed at European readers who are less likely to be aware of this than Americans) – troglodytids are essentially an entirely American group, and a mostly South American one at that given that there are only nine species in North America compared to nearly 70 in South America (and it’s actually Central America that is the center of their diversity). Only one species has colonized Eurasia, Troglodytes troglodytes (we just call it the Wren of course, but if you’re American it’s the Winter wren). As elucidated by molecular data, its biogeographical history is actually bizarrely complicated (Drovetski et al. 2004).

Finally… a possible rayadito

Anyway, to get back to the Falklands birds, some of the other wren-like birds reported from the islands were almost certainly not troglodytids. Take the small passerines observed during the 1930s by C. Bertrand on East Sea Lion Island. They were smaller than wrens, ‘frail’ in appearance, possessed an obvious yellow eye-stripe, and moved rapidly up and down tussac stems. None of the verified Falkland passerines look like this, so Woods (1988) suggested that they might have been Thorn-tailed rayaditos Aphrastura spinicauda. Thorn-tailed rayaditos are quite common in temperate southern South America, and they more or less match Bertrand’s description. Perhaps they were vagrants to the Falklands, or (as with the Andean tapaculo and others discussed above) maybe they were natives that have since become extinct. Though it’s a woodland bird, it will apparently make do in areas where there is shrubby vegetation, so it’s certainly possible that they would be ok on the Falklands.

What are rayaditos? They’re furnariids (ovenbirds), but furnariids that have evolved to live in temperate woodland. Given the really cool work on furnariid ecomorphological diversity, adaptational shifts, phylogeny and nest diversity that’s recently been published (see Fjeldså et al. 2005 and Irestedt et al. 2006), I’d like to say a lot more about them, but that will have to wait, and I have to end this here.

Coming next… in quest of anguids. And for those of you who come here for the pterodactyls and dinosaurs, I’ll be posting soon on pterodactyls and dinosaurs.

The image above is a Thorn-tailed rayadito photographed in Tierra del Fuego, and not on the Falklands. It’s from here.

For the latest news on Tetrapod Zoology, do go here.

Refs - -

Ali, S. & Ripley, S. D. 1969. Handbook of the Birds of India and Pakistan, Together With Those of Nepal, Sikkim, Bhutan and Ceylon, Vol. 3. Oxford University Press (Oxford and Bombay).

Beehler, B. M. 1991. A Naturalist in New Guinea. Texas University Press (Austin, Texas).

Bennett, A. G. 1926. A list of the birds of the Falkland Islands and dependencies. Ibis 2, 306-333.

Clement, P., Harris, A. & Davis, J. 1999. Finches & Sparrows. Christopher Helm (London).

Day, D. 1989. The Encyclopedia of Vanished Species. Universal Books (London).

Drovetski, S. V., Zink, R. M., Rohwer, S., Fadeev, I. V., Nesterov, E. V., Karagodin, I., Koblik, E. A. & Red’kin, Y. A. 2004. Complex biogeographic history of a Holarctic passerine. Proceedings of the Royal Society of London B 271, 545-551.

Fjeldså, J., Irestedt, M. & Ericson, P. G. P. 2005. Molecular data reveal some major adaptational shifts in the early evolution of the most diverse avian family, the Furnariidae. Journal of Ornithology 146, 1-13.

Irestedt, M., Fjeldså, J. & Ericson, P. G. P. 2006. Evolution of the ovenbird-woodcreeper assemblage (Aves: Furnariidae) – major shifts in nest architecture and adaptive radiation. Journal of Avian Biology 37, 260-272.

McDowall, R. M. 2005. Falkland Island biogeography: converging trajectories in the South Atlantic Ocean. Journal of Biogeography 32, 49-62.

Shuker, K. P. N. 1998. A supplement to Dr Bernard Heuvelmans’ checklist of cryptozoological animals. Fortean Studies 5, 208-229.

Simpson, G. G. 1976. Penguins: Past and Present, Here and There. Yale University Press (New Haven and London).

Wace, R. H. 1921. Lista de aves de las isles Falkland. El Hornero 2, 194-204.

Williams, J. G. & Arlott, N. 1980. A Field Guide to the Birds of East Africa. Collins (London).

Woods, R. W. 1988. Guide to Birds of the Falkland Islands. Anthony Nelson (Oswestry).

- . 1993. Cobb's Wren Troglodytes (aedon) cobbi of the Falkland Islands. Bulletin of the British Ornithologists’ Club 113, 195-207.