Kangaroo Grass

The paradox of the Paradise Parrot

'The most fatal change of all for the grass-seed-eating Paradise Parrot was that the more nutritious of the native cereals, like the Oat or Kangaroo grasses, were dying out under overstocking by sheep and cattle. What still remained were not allowed to produce their seed. Droughts accentuated their food scarcity to the point of starvation and in particular, it has been definitely recorded that the 1902 drought absolutely wiped the 'ground parrot' out in some districts............When all the above factors are taken into account, it must be admitted that the extermination of Psephotus pulcherrimus does not provide a very difficult problem.' Cyril Henry Harvey Jerrard, 1924

I thought it fitting that the subject of the first article I prepare should be the species after which my ecological consulting business is named. I provide an overview of my own ideas on the subject of the extinction of this species. I cannot claim to have elucidated a satisfactory, detailed explanation for the passing of the Paradise Parrot but I hope the thesis posited does justice to the species that so inspired those lucky enough to have observed it.

What do we know about the demise of the Paradise Parrot? To be sure, Queensland's reputation for destroying natural capital with gay abandon is well earned, having sustained some of the highest rates of native vegetation clearing in the country, and, at times, the world, at various times in the second half of the 20th century. Cynics might be tempted to suggest that we need look no further than this dubious record to find our answer. However, the Paradise Parrot's decline swiftly followed European settlement, suggesting catastrophic changes to the species' habitat, at least a century before the state-sanctioned destruction of native vegetation proceeded apace.

The parrot

The Paradise Parrot was a medium-sized parrot (about 30 centimetres long). The male was brightly coloured with a black cap, turquoise-green chest and underparts, brown back and bright red on the lower abdomen and shoulders. The female was less colourful, being predominantly pale brown suffused with light blues on the throat and underparts and with a smaller red shoulder patch. The species occurred mainly in inland areas of the south-eastern portion of Queensland in grassy open woodlands and open forests, although there are also records of the species having been observed in what are now the inner suburbs of Brisbane. Penny Olsen's book, Glimpses of Paradise, provides a comprehensive background on the history of the species since European settlement.

Ground-foraging granivorous birds throughout Australia have been affected by land use practices since European settlement. However, the assemblage in the southern half of Queensland and northernmost parts of NSW has arguably experienced the greatest upheaval of any in the last 200 years. In this region, one species has almost certainly become extinct (Paradise Parrot) and the ranges of at least five others have experienced major contractions either northwards (Squatter Pigeon, Black-throated Finch and Star Finch) or southwards (Turquoise Parrot and Diamond Firetail). Accompanying the loss of these species has been the expansion in range into this region of a suite of granivorous species that were previously uncommon or only occasional visitors. Foremost amongst these are the Galah and Crested Pigeon. Others include the Cockatiel and Double-barred Finch. A handful of species, including the Peaceful Dove, Red-browed Finch, Plum-headed Finch and Chestnut-breasted Mannikin survived the turmoil, although there is evidence that the latter two species may have experienced declines.

In effect, identifying the causes of the extinction of the Paradise Parrot is as much about explaining the causes of this upheaval and why other regions in Australia that have experienced greater and more widespread environmental degradation have managed to retain (albeit by the skin of their teeth in some cases) most elements of the granivorous bird assemblage present at the time of European settlement (that is, as far as we are aware). It is tempting to attribute the decline of the assemblage solely to catastrophic modification of habitat that accompanied pastoral expansion in the region. But differences in the timing of declines of the species in the assemblage suggests that the story is not so simple. For example The Black-throated Finch and Diamond Firetail were still relatively numerous in many parts of the region until the 1970's.

The paradox

CHH Jerrard was a grazier in the Burnett region of southern Queensland. He was possibly the last person to have seen a living Paradise Parrot. His quote at the beginning of this article clearly suggests he believed the disappearance of the species was anything but paradoxical. The reason I use the term is that I believe there is a useful comparison to be made between the fate of the Paradise Parrot and alarming declines in populations of many vertebrate fauna species found in the tropical savannas of Australia documented in the last 10 to 20 years. These declines have been described by some observers as paradoxical in that, on the face of it, the savanna ecosystems in the northernmost third of the Australian continent appear to have been far less disturbed than 'similar' ecosystems in the south, particularly the temperate grassy woodlands. Whereas more than 90% of the latter, which once covered millions of hectares across the southern half of the continent, have been completely destroyed and the structure and species composition of the majority of remnants highly modified, only a very small proportion of the tropical savanna ecosystems have been cleared.

However, what is becoming increasingly apparent is that anthropogenic disturbances to these ecosystems (including those caused by 'ecological proxies' of Homo sapiens, such as beef cattle), while appearing to be quite subtle may be just as profound as the vegetation clearing undertaken on a massive scale in the woodland ecosystems in southern Australia.

The theory

The composition of pastures in Australia

Changes in the composition and structure of the grassy ground layer in previously ungrazed (except by native grazing species like kangaroos and wombats) woodlands and open forests in Australia that follow the introduction of grazing livestock have been noted since the time of the earliest European pastoralists in southern Australia. The structure and composition of the grassy ground layer of woodlands and open forests into which the early graziers introduced their flocks would have varied in space and time, influenced primarily by fires ignited by lightning and Aboriginal people as well as climatic conditions.

The transformation of the grassy ground layer across large swathes of central-southern Queensland was probably fairly rapid. As a consequence, there is limited evidence of the composition of grassy communities prior to the advent of pastoralism, although there seems to be general acceptance that, except on some areas of soils derived from basalt and some alluvial deposits, Kangaroo Grass was frequently the dominant species. Early settlers in the Burnett region, the location of the last known population of the Paradise Parrot, commented on the change from Kangaroo Grass-dominance to Black Spear Grass-dominance in the understorey throughout extensive areas of grassy woodlands in the thirty five years following the introduction of livestock.

The diet of the Paradise Parrot

The lack of basic information on the biology of the Paradise Parrot makes it very difficult to identify the main dietary items of the species. We can look to the diets of its closely related congeners, the Hooded and Golden-shouldered Parrots, to provide some clues. The small amount of research conducted seems to suggest some degree of dietary specialisation in these species. However, this assertion cannot be made with complete confidence as the studies conducted to date, while providing very good data on the plant species utilised by the two parrot species, do not provide information on those species consumed compared to the full range of species available.

A major feature of granivory in the tropical savannas is the strong component of seeds from annual grass species in the diets of most species. Although subtropical and temperate grassy ecosystems have been extensively destroyed and modified, sufficient remnants remain to suggest that annual grass species have only ever formed a minor component of these ecosystems, at least in very recent geological time scales. The distinction between annual and perennial species may in fact be of relatively minor relevance. The more pertinent feature of the diet of many tropical granivores may be the reliance on a fairly small number of species that are both relatively common in the habitat occupied by granivores and produce very large amounts of seed. Both the Hooded Parrot and Golden-shouldered Parrot display this characteristic, although because of the geographical separation in their ranges the plant species utilised by both species differs.

So, is it possible that the transition from Kangaroo Grass to Black Speargrass dominance in the native pastures of southern Queensland marked a transition from a state containing reliably available seed-sources for the Paradise Parrot to one with much reduced availability of preferred species? It is quite possible that the shift in dominant species per se was not the major cause of the decline because evidence from studies indicates that neither species is especially important in the diets of granivorous birds in Australia (although it bears noting that there have been few comprehensive studies into the diet of granivorous birds in Australia). Both these species have relatively large seeds with long awns which may make them more difficult to process by seed-eating birds, although several Sarga species (native sorghum) favoured by threatened granivores like the Gouldian Finch (Erythrura gouldii) also have long awns (long, bristle-like appendages, such as can be seen on unprocessed wheat seeds). Perhaps more importantly, when still retained on the plant, their seeds may be relatively more difficult to access. Kangaroo Grass inflorescences have a fairly complex structure in which seeds are surrounded by several leaf-like bracts and the long awns of Black Speargrass twist and intertwine to form a dense, bristly clump of seeds, potentially making their extraction energetically more costly.

By contrast, there is reasonably strong evidence that several of the dominant grass species that persist after the transition from Kangaroo Grass-dominance in temperate native pasture following the introduction of livestock, particularly Wallaby Grasses and Redleg Grass, form an important part of the diet of many granivorous birds in southern Australia. In fact, the current distribution of the Turquoise Parrot and Diamond Firetail fairly closely matches the main distribution of Wallaby Grasses and Redleg Grass, although this may be reflective of other underlying processes.

Conclusions

CHH Jerrard felt that there was little mystery about the demise of the Paradise Parrot. The use of the word 'paradox' is perhaps a little dramatic but it serves to draw attention to the fact that what happened to the Paradise Parrot in little more than half a century may just be taking a little longer for a whole host of other vertebrate species in Australia. Identifying the processes underlying the paradox is critical, especially with the looming spectre of climate change and grand designs for the expansion of agriculture across northern Australia being discussed more and more at the highest political levels. In CHH Jerrard's time, the study of ecology was in its infancy and the conservation of biology promulgated by a tiny minority. Modern Australia has no such excuses.


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