Australia has a diverse array of parrot species. Between them they span the entire continent, from the wet tropics to the arid interior, and everything in between. Most are unique to Australia, and they provide some of the most distinctive sights and sounds of this country.
The extravagantly-hued Rainbow Lorikeet was declared to be Australia’s most common bird after last year’s Backyard Bird Count. At the other extreme of the conservation balance-sheet, the Orange-bellied Parrot, which migrates across the ocean between Tasmania and the mainland, is in a desperate situation with fewer than 50 left in the wild.
Where I live south of Adelaide, I can easily see several species of parrot before breakfast. Galahs, Rainbow Lorikeets, Crimson Rosellas, Yellow-tailed Black Cockatoos and Red Rumps are the ones I see most regularly.
Although these are everyday species, I have never got over the novelty of having parrots as common garden birds. By the time I moved to Australia at the age of 10, I was already thoroughly bird-struck, and it was like arriving in paradise. It still is.
There are many species of parrot that I have yet to see, but there is one unusual group of species floating at the top my bucket list: the Ground Parrots and Night Parrots.
Life down low
Many species of parrot feed on the ground, but there are only a handful of species in the world that live out their entire lives – eating, resting and nesting – at ground-level. Night Parrots and Ground Parrots are the only Australian parrots to have adopted this uncommon and specialised lifestyle.
They are famously cryptic and hard to detect. They are well-camouflaged, rarely fly, and their preferred survival strategy is to hide or run away from potential predators – including us.
Night Parrots are so good at this that they evaded detection in Australia’s vast arid zone for several decades, during which time they were feared to be extinct. It took ecologist John Young 15 years of diligent effort to re-discover a living population – and to capture the first ever photograph and video footage of a living Night Parrot – in 2013. The species, previously a near-myth, was instantly catapulted to rockstar status – but it still doesn’t sign many autographs.
Ground Parrots are slightly less elusive, but are still rare to spot. If they are located at all in their swamp and heathland habitats around the continental margins, it is usually by their call.
More diverse than we thought
Scientists are still unraveling the ecology of these species, especially the Night Parrot, whose habits have only been documented in earnest over the last five years. The evolutionary history of this group of birds is also not very well understood.
Until a few years ago, only one species of Ground Parrot was known to exist, but a genetic study published in 2010 split the species into two, implying that a more interesting evolutionary story has unfolded for these birds over the last couple of million years.
The tiny, isolated population in south-west Western Australia was found to be a species in its own right. This is now known as the Western Ground Parrot, Pezoporus flaviventris. The population clings on to survival in heathland habitat near Esperance.
The Ground Parrot populations in Queensland, New South Wales, Victoria and Tasmania are now known as the Eastern Ground Parrot, and retain the previous scientific name of the species, Pezoporus wallicus. This species lives in swamps and heathland habitats on the mainland, and in button-grass moorlands in Tasmania.
The Eastern Ground Parrot is much more secure than its western counterpart, but it is extinct in South Australia, thanks mainly to the draining of its former swampy habitats. This stands as a warning of what could happen if we fail to protect the remaining Ground Parrot populations from threatening processes.
Palaeontology is just slow ecology
In case I never get to see any of these unusual birds in the wild, I’m prepared to settle for studying their skeletons to try and find out more about their evolutionary history. (Bones are famous for their inability to run away.)
In my palaeontology work I have spent many hours looking at parrot bones down a microscope. As with all bones, they have evolutionary stories to tell if you study them closely.
For example, all parrots share the same general structure of the lower leg bone (the tarsometatarsus). It is relatively short, and at the bottom are the trochleae, where the toe bones attach. Parrots have four toes, two pointing forward and two pointing backwards. Unlike most other birds, in parrots the fourth trochlea is bent around to the back of the tarsometatarsus, which makes the fourth toe face the rear.
This foot arrangement works well as a grasping tool – as anyone who has watched a parrot deftly bringing its food up to its beak will know.
The bones of Pezoporus
The same basic tarsometatarsus structure is common to all parrots, but the anatomical detail differs between species, which allows us to tell their bones apart. All members of a species share unique inherited features of the skeleton, which reflect both their ancestry and their lifestyle.
So, what is the tarsometatarsus like in Ground Parrots and Night Parrots? Some of that we can answer, and some of that we can’t as yet.
The Eastern Ground Parrot has an exceptionally elongate tarsometatarsus. Compared to other parrots, it looks like this bone has been grasped at both ends and stretched.
The stretch-limo legs of the Eastern Ground Parrot relate to its terrestrial lifestyle and gait: unlike other parrots, which have short, stubby legs and can’t walk without rolling heavily from side to side, they are said to move briskly without the characteristic parrot waddle.
Do the Western Ground Parrot and Night Parrot have a tarsometatarsus with the same stilt-like proportions? We might assume so, based on a shared ground-dwelling lifestyle, but without skeletons to examine that’s just guess-work at the moment.
In this video of a Western Ground Parrot, it certainly seems to move briskly without waddling, so it might well have an elongate leg similar to its Eastern cousin. But observations of the Night Parrot since its rediscovery indicate that it sometimes moves by hopping like a kangaroo, and this video footage seems to show it scurrying in a rodent-like fashion along the ground. Does it need stilts to move like that? Maybe not.
There are several different types of tarsometatarsus that I have seen in fossil collections from various parts of Australia that are similar enough to know that they are Pezoporus, but different enough to see that they don’t belong to the same species.
To work out which species these bones belong to, which will tell us about the past geographical distributions of these birds, it will be necessary to compare the fossil leg bones with modern skeletons of all three living species of Pezoporus.
This is easier said than done, as remains of the Western Ground Parrot and the Night Parrot are as scarce as you would expect, and skeletons are non-existent. It will involve CT scanning preserved museum skins to study the bones inside.
Only then will it be possible to tell whether the fossil bones belong to the three living Pezoporus species, or if any of them belong to extinct relatives that we don’t yet know of. It’ll be a labour of love, but considering it took more than a decade of walking through spinifex to find a living population of Night Parrots, I think that’s a pretty good deal.