Keeping the common birds common

by Sarah Lloyd

Swift Parrot
Swift Parrot

‘The feathered tribes of Van Diemen’s Land are numerous ... The land birds, generally speaking … are all of them curious and beautiful. The number of the various kinds of parrots and paroquets [sic], clothed in the most beautiful plumage, are almost beyond description …The pigeons are by far the most beautiful birds on the island …The birds that may be called game are very numerous, with the exception of the emu …The quail of which there are three kinds are far more numerous in many parts of the island than the partridge in England …Snipes are found in great abundance from September to March in the lakes and wet valleys.’ (J. Bischoff 1832)

The above quote, written by naturalist James Bischoff in 1832, gives an inkling of the abundance of birds in Tasmania not long after the British arrived. More recent writings by ornithologists Michael Sharland and Bob Green also suggest abundance. In 1958 Sharland described Swift Parrots as ‘very common’. It was not known at the time whether they bred around Hobart, or even if they migrated. Now we know that Hobart and other areas in the southeast are breeding hotspots for this bird, and that they do indeed leave Tasmania for the Australian mainland, undertaking the longest migratory flight of any parrot species in the world. Tragically, we now know that they are among the rarest birds in the country.

In 1995 Bob Green described Flame Robins as ‘the most widespread robin in Tasmania’. Five years later they were included in The Action Plan for Australian Birds 2000 (Garnett & Crowley 2000) because the frequency of observations declined substantially at the edges of their non breeding range; the reporting rate for Flame Robins more than halved in the twenty years between the first Atlas project run by Birds Australia in 1977-81 and the second, on-going, Atlas.

forty-spotted Pardalote
Forty-spotted Pardalote

In 1986-87 extensive surveys of the endemic Forty-spotted Pardalote found that the population was approximately 3,520 birds. In 1993-97 Sally Bryant, when reassessing the colonies, concluded that they were secure, indeed flourishing, in certain areas such as Maria, Bruny and Flinders Islands. By 2009-2010 during another assessment, the colonies had crashed. With so much attention focussed on the other species in the growing list of threatened plants and animals in Tasmania 'Nobody seemed to notice that the Forty-spotted Pardalote had started to slip away.' (Bryant & Tzaros) But they had. Ecologist Matt Webb detected significant declines during his studies in 2005-2007.

My experience of ‘Forty-spots’ was virtually non existent until I started surveying birds at Murrayfield on Bruny Island in December 2008. I was keen to check the several colonies known to occur on this large property. At McCrackens Gully, where a thriving population had been observed during previous surveys, I detected only one bird.

As is usually the case, the decline of a species can usually be attributed to more than one factor. The Forty-spotted Pardalote may be one of the first species in Tasmania to succumb to the changing climate. Southern Tasmania seemed to suffer more than other regions during the recent drought; many of the scattered white gums, with which the forty-spots have a very close association, were either dead or dying.

For five years I have been conducting bird surveys at a large farming property at Cressy in the northern midlands and more recently I started surveying birds at a property near Ross. One of the questions I am frequently asked after doing a survey is ‘did you find anything rare?’ Finding rare and threatened species may be the emphasis of a botanical survey, but when doing a bird survey my main objective is to find all the bird species that should be there.

For any given area in just about any eucalypt forest in Australia there is a range of bird species - a bird assemblage - that should be present. For example, there will be at least one species of fairy-wren (the Superb Fairy-wren in Tasmania). Other birds that you would expect to see include ground foraging species such as scrubwrens and robins; mid storey birds such as thornbills and whistlers, and canopy feeders such as pardalotes and honeyeaters. All these birds have important ecological roles. To paraphrase Nick Mooney who spoke eloquently at the recent Bruny Island Bird festival, it is the common birds that drive the system. They are the ones that consume copious quantities of insects, they are the ones that pollinate the plants and they are the ones that disperse the seeds. (Of course many other species: bats, insects, spiders etc are also involved in these tasks.)

One of my major concerns is that the conservation emphasis on the reservation of vegetation communities (particularly the presence of certain eucalypt species or rare and threatened plants) rather than looking at the whole biota may be having an adverse impact on the bird species hitherto regarded as common.

This conservation emphasis probably dates back to the introduction of wood chipping in Tasmania and was further exacerbated during the Regional Forest Agreement.

In the early 1970s reserves were based on scenic rather than scientific values. After the publication of Conservation of Major plant communities in Australia and Papua New Guinea by Specht et. al. in 1974 there was an attempt to reserve representative vegetation communities at different altitudes and on different geological substrates. This came about because of the signing of a Memorandum of Understanding between the State and Commonwealth governments which was a condition of Tasmania being granted continuing woodchip licences (Jones et. al. 1999). The Regional Forest Agreement further attempted to protect under-reserved vegetation communities in a Comprehensive, Adequate and Representative (CAR) reserve system.

Scarlet Robin
Scarlet Robin

But are these reserves adequate for the maintenance of bird diversity? I have been surveying bird south of Cressy since 2006. One area, which is classified as ‘grassy woodland’ has a wonderful array of rare and threatened plants, including rare orchids. When I began the surveys it had a reasonably good bird fauna including all four cuckoo species that occur in Tasmania, three species of robin (Flame, Scarlet and Dusky); numerous aerial feeding insectivorous birds such as Tree Martins and Dusky Woodswallows. But honeyeaters, particularly the common and widespread Yellow-throated Honeyeater and the dry forest inhabiting Black-headed Honeyeater were conspicuous by their absence. Last spring (2010) there were no woodswallows and no robins at this survey site. The area is heavily grazed by introduced and native herbivores (sheep, deer and wallaby) and the vegetation lacks structural diversity - i.e. layers; there is very little dense understorey. In fact, the most valuable dense understorey that provides safe nesting sites for fairy-wrens and thornbills is gorse. The landowner, to his credit, is conscientious about the eradication of this invasive plant and between the first and second surveys large patches were eliminated. But this left no habitat for the fairy-wrens.

Another survey site on the property has a conservation covenant because black peppermint (Eucalyptus amygdalina) on sandstone is under-reserved. But the area has very little mid storey and understorey vegetation, the eucalypts are dying and the area is dominated by Noisy Miners, a large aggressive native honeyeater. Consequently it has none of the smaller birds that should occur in such a habitat. My prediction is that this area will continue to deteriorate because of the absence of these species.

In stark contrast, the healthiest site on the property has no formal protection. It supports a rich bird fauna because it has structurally complex vegetation with many layers present. These layers of vegetation provide birds with places to forage, shelter from inclement weather and predators and safe nesting sites. Birds are not concerned whether plants are rare or threatened, they simply need them to be present!

Not only is there an emphasis on reserving plant communities but also on particular plant species. I came across the following in a paper written in 2003:

‘The occurrence of endangered plant species has been shown to be unrelated to general remnant condition (Kirkpatrick & Gilfedder, 1995) and these species may require special management that must take precedence over any efforts to improve habitat for non-threatened birds’. (Macdonald & Kirkpatrick 2003).

Who is deciding what species are 'non-threatened'. As far as I am aware, apart from about twelve people who contribute regularly to Birds Australia’s ongoing Atlas project, there is very little on-going monitoring of terrestrial species in Tasmania apart from the Sound Idea project and my farm surveys mentioned above. Based on my observations made in the field and by listening to recordings, I would be very reluctant to classify any bird as non-threatened, especially given the rapidly changing agricultural landscape, driven by the unrealistic desire for Tasmania to be the ‘food bowl of the nation’ and the continuing forestry operations which seem to accelerate whenever there is mention of stopping logging in old growth or high conservation forests.

The history of white settlement in Tasmania is one of exploitation of our natural resources. It is no coincidence that the areas richest in birds and other biodiversity were those areas that were cleared and farmed. By 1830 there were one million hard hoofed animals (mostly sheep) grazing on land mostly in the midlands.

Towns and cities are usually situated near waterways and productive land, so they too coincided with areas of greatest bird diversity. Information gathered during the Sound Idea acoustic bird monitoring project demonstrates that some of the settled areas retain a rich bird fauna. In fact semi-urban areas within the St Helens Township for example now support more native bird species than semi-cleared farmland in the northern midlands.

A recent survey I conducted in the Eastern Tiers near Ross gave me cause for cautious optimism. Sheep, long used as a ‘conservation tool’ for the preservation of threatened plant species in the midlands, no longer have access to the bush. The eucalypt regeneration after just four years of their exclusion is remarkable; the bird fauna is encouraging.

But I will keep in mind the sentence:

‘Nobody seemed to notice that the Forty-spotted Pardalote had started to slip away.’

References:
- Bischoff, J. (1932) Sketch of the history of Van Diemen’s Land and an account of the VDL Company. John Richardson, Royal Exchange, London
- Bryant, S. & Tzaros, C. (2010) 'A Forty-spot of Trouble'. Wingspan. Winter Vol.20 No.2
- Green, B. (1995) The fauna of Tasmania: birds. Potoroo Publishing, Launceston
- Garnett, S.T., & Crowley, G.M. (2000) The Action Plan for Australian Birds. Environment Australia
- Garnett, S. (2001) Winners and Losers. Wingspan Vol. 11 No 4 December 2001
- Jones, D., Wapstra, H., Tonelli, P., & Harris, S., (1999) The Orchids of Tasmania. Melbourne University Press, Melbourne
- MacDonald, M.A. & Kirkpatrick, J.B. (2003) 'Explaining bird species composition and richness in eucalypt-dominated remnants in subhumid Tasmania'. Journal of Biogeography, 30, 1415-1426. Blackwell Publishing Ltd.
- Sharland, M. (1958) Tasmanian Birds. Angus & Robertson. Sydney.

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