Tasmania’s bush birds – a bleak outlook
by Sarah Lloyd
It's hard not to be pessimistic about the state of bush birds in Tasmania. There are undoubtedly numerous factors leading to their decline with different species affected differently depending on their feeding strategies, habitat preferences and lifestyles.
Anyone familiar with the Tasmanian landscape even a decade ago will have noticed significant changes – some of us have been living here nearly all our lives. Forty years ago the drive south from Burnie along the Murchison Highway passed through corridors of Gondwanan rainforest, the largest remaining tract of cool temperate rainforest in Australia. Now it is a patchwork of industrial-scale plantations of pine and eucalypt as far as the eye can see. Increased irrigation and the push to double agricultural production to make Tasmania the 'food bowl of Asia' (are poppies and eucalypts really that tasty?) has changed the rural landscape from one of small and large patches of bush interspersed with paddocks and 'rough pasture' to vast cleared areas that from the air resemble interlocking crop circles where irreplaceable paddock trees have been sacrificed to make way for pivot irrigators. Other areas of native vegetation have been selectively logged (removing centuries-old habitat trees in the process), clearfelled, burned and 'converted' to plantations of shining gum (Eucalyptus nitens), or they have been fragmented, invaded by weeds, grazed or subjected to frequent burning. I believe these changes are affecting many bird species with some extremely worrying trends.
For the past nine years I have been surveying birds at a large property south of Cressy at the base of the Great Western Tiers in Northern Tasmania. I met the landowner at a field day of invited community members to discuss Forest Stewardship Council (FSC) accreditation for logging operations on the southern slopes of the Tiers. I represented Birds Tasmania. The landowner generously allows researchers on his property to study everything from its rich history to the botanical riches that abound in the grassy woodlands. Thus far the birds had not been surveyed but the landowner expressed interest.
Relatively large areas of native vegetation (mostly grassy woodland) remain at the Cressy property of approximately 17,000 hectare (half of this extends up the forested slopes of the Tiers). In 2006 five 2-hectare survey sites in vegetation of varying extent and condition were established on the farmland and four in the forests of the Tiers. They are surveyed using standard methodology i.e. 20 minutes surveys as early in the morning as possible noting all bird species seen or heard.
Surveying the Cressy farm was an exciting project - at least initially. The property encompasses large and small areas of remnant bush; paddocks with old, hollow-bearing trees; permanent waterways and dams of various sizes; plantations of pine and eucalypt; and more recently, crops watered with pivot irrigators. When the surveys began the birdlife was varied with many different species of waterbirds, three species of robin and all four migratory cuckoos that occur in Tasmania. Aerial feeding insectivorous species such as Dusky Woodswallow, Tree Martin and Welcome Swallow were 'in abundance', according to my first report. But nine years on some of these species have declined alarmingly or no longer occur on the property. This is particularly worrying given that Tasmania was in the grip of severe drought when the surveys began and there was an expectation that things would improve not worsen. Of particular concern are the species generally regarded as common especially three medium-sized birds: Grey Shrike-thrush, Golden Whistler and Yellow-throated Honeyeater. Grey shrike-thrush were recorded at two of the five search areas in 2006 and 2007 but have not been recorded since 2008. Golden Whistlers were recorded at two search areas in 2006 and one was recorded near a search area in 2009. During the nine years of surveying there have only been two records of the Yellow-throated Honeyeater near one search area and the 'common' endemic Black-headed Honeyeater, a bird of dry forests and woodlands, has never been recorded on the property during the surveys.
The absence of these birds had me baffled for some time, after all there's plenty of what looks like 'quite nice bush'. A landowner and a bureaucrat with little knowledge of birds suggested that they may never have occurred there; a top government botanist questioned the value of bird surveys because birds 'just fly around'. But anyone who has ever conducted bird surveys knows that bush birds have quite a small home range, especially during the breeding season, and just about every woodland or forest site in Tasmania - even small bush remnants - should support the common and very vocal Grey Shrike-thrush, Yellow-throated Honeyeater, Golden Whistler and Black headed Honeyeater. During my previous farm surveys these species were present at almost every site. (My previous experience includes surveying three farms in the Meander Valley for two years in 2001-2002 for Birds Australia's Birds on Farms project; 15 properties along the northwest coast and 20 on King Island for the 'Biodiversity Indicators for Sustainable Farm Management' project initiated by Richard Donaghey and several sites at Murrayfield, Bruny Island.)
To conduct the surveys my partner Ron Nagorcka and I camp for two days at 'Red Hill', one of the five search areas on the farm, and the one that is the richest for birds. (It has no threatened plant species and therefore no formal protection.) It is adjacent to an extensive area of native vegetation and because the aforementioned birds are extremely vocal, especially during spring and early summer, they would certainly be detected if they were in the area. Why where they not there? A visit to another grazing property east of Ross suggests a possible reason for their absence.
In January 2010 I approached the owner of the Ross property after reading a report in the Examiner that described measures to protect large areas of land in the Ross/Campbelltown area (The Examiner December 30 2009). I expressed my concerns that conservation covenants and management regimes focus on botanical values and threatened plants with limited consideration of the rest of the biota. I proposed setting up sites on the property and to undertake regular bird surveys. My suggestions were greeted positively and I have subsequently surveyed the property on three occasions.
In November 2014, a month after surveying birds at Cressy, we set up camp in the Eastern Tiers at a site of relatively open dry grassy woodland adjacent to thicker bush with an impenetrable (at least to us) understorey layer of bracken fern and sagg. And what a relief and joy it was to hear the familiar songs of Grey Shrike-thrush and Yellow-throated Honeyeater not long after we arrived!
The property is different from the Cressy property in several respects. There is a clear delineation between the farmed areas and the conservation areas, and the climate is usually considerably drier. In 2014 the cleared farmland was drought affected, but in stark contrast, the bush in the Eastern Tiers looked remarkably healthy with bird populations of some species flourishing. (For approximately 200 years the Tiers were used as ‘run country’, a practice that has been widely viewed as a relatively benign use of the bush. The sheep were excluded 2007/2008.) In my 2014 report I noted:
the number of birds and species present at the survey sites in 2014 is remarkably similar to those found in November 2011. For instance, Flame Robin and Satin Flycatcher were again recorded at or near Site 3 and a family of Superb Fairy-wren was found at Taylor’s Hill - in almost exactly the same place!
Numbers of some species, most notably Yellow-throated Honeyeater, Striated Pardalote, Grey Shrike-thrush, Yellow Wattlebird, Black-headed Honeyeater and Eastern Spinebill seem to have increased. This can possibly be attributed to the recovery of the vegetation since sheep were excluded in the summer of 2007/08 and the favourable (wetter than usual) conditions of the subsequent four years. It was interesting to observe that the honeyeaters were not foraging on the black peppermint flowers, but were searching for invertebrates on the foliage of the white gums.
After several days of observation in the Eastern Tiers it was not hard to conclude that the absence of some species at the Cressy property could be attributed to the absence of large continuous tracts of suitable dense mid story and understorey vegetation where birds can nest, roost and take refuge from inclement weather and predators. There is certainly not a lack of understorey and midstorey vegetation, but it is sparse and there are few (if any) areas that have not been regularly grazed by cattle, sheep and/or feral deer whose activities continually degrade and fragment the understorey. The fragmentation of bush at a landscape scale is often discussed, but my observations suggest that fragmentation of the understorey on a much smaller scale is also detrimental to certain species.
Discussions with the Cressy landowner indicate that 'light' grazing by cattle or sheep to control the growth of grass usually occurs annually. (We encountered cattle at two survey sites during the 2014 surveys and all areas had evidence of recent grazing.) This may actually favour some threatened plant species as it eliminates grassy competitors. However, it fragments, albeit gradually, the continuous layer of vegetation so essential to the survival of some birds. It makes you wonder about the efficacy and value of conservation covenants – are they there to protect threatened species, particularly plants and vegetation communities, or are they established to maintain and possibly enhance biodiversity? It seems this very much depends on the commitment of the landowners, how much they understand the issues and how they manage their properties as a result. Management for flora without the consideration of effects on fauna will not conserve biodiversity in the long run.
The lack of extensive areas of understorey vegetation may explain the absence of Yellow-throated Honeyeater, which nests in the understorey, but the absence of Golden Whistler which has not been recorded on the farm since 2009, nor in the recovering production forest on the slopes of the Great Western Tiers OR at the Eastern Tiers in 2014 where it was recorded at two survey sites in 2011 - may point to more sinister causes.
The Golden Whistler is a very vocal species but the birds themselves are rarely seen because male birds usually forage for invertebrates high in the canopy foliage of eucalypt, and the females usually forage lower in the canopy or in the midstorey vegetation.
As mentioned above, there are few remaining large tracts of untouched native vegetation outside National Parks in Tasmania. The Eastern Tiers, Great Western Tiers, Birralee and Frankford, Weegena, Mathinna, Fingal and north Scottsdale—to name but a few—are now a mosaic of native vegetation interspersed with plantations at various stages of maturity of mostly shining gum. At some stage in their cycle these trees are sprayed to 'protect ... from severe defoliation by native insect pests' including eucalyptus leaf beetles Paropsisterna spp., Eucalypt weevil Gonipterus scutellatus, autumn gum moth Mnesampela privata and gum leaf skeletoniser Uraba lugens. The chemical most often used is Alpha-cypermethrin, listed by the FSC as a 'highly hazardous’ pesticide'. In fact it is so hazardous that there is a 14 day exclusion period prohibiting entry by forestry workers to plantations that have been sprayed.
Alpha-cypermethrin is an indiscriminate chemical that also kills beneficial invertebrates such as the zig-zag ladybird Cleobora mellyi, plague soldier beetle Chauliognathus lugubris and no doubt numerous others. Not only does it drastically reduce insect numbers forcing birds to forage over a greater area to fill all their dietary requirements, but it is likely that birds that glean insects from the foliage of eucalypts in the plantations and/or in adjacent bush will be adversely affected when they ingest insects that have been sprayed.
Crops such as tomatoes, lettuce, cereals, corn, soybean, rice, beans, sunflower, canola, lucerne, pasture, field peas and lupins are also sprayed with Alpha-cypermethrin. The chemical is 'dangerous to bees' and should not be spray when there are plants in flower where bees are foraging. It is also 'dangerous to fish' and should not contaminate any waterways or water bodies. This chemical, and no doubt numerous others, is likely to affect adversely affect all insectivorous bush birds including Welcome Swallows and Tree Martins, foliage gleaners such as Golden Whistler and ground foraging birds such as robins.
Understorey vegetation: gorse and small birds
When the surveys in 2006 began Ron and I camped at 'The Pond', another of the survey sites on the Cressy property. The Pond is a large dam that over the years has had an entertaining variety of waterfowl, and a deafening chorus of frogs. It had scattered live and dead eucalypts, small copses of regenerating silver wattle with patches of gorse forming a dense but patchy understorey. The ground layer vegetation had a mix of native and introduced grasses, small herbaceous plants and numerous orchids. Eight bird species were recorded on the site in 2006; by 2014 only four species were recorded.
In 2006 Superb Fairy-wren, Yellow-rumped Thornbill and Brown Thornbill were using the gorse for nesting, sheltering and foraging and numerous skinks were basking in the sun close to the plants only to retreat to the prickly shelter whenever I approached. By 2000 the gorse had been sprayed and left in situ but by the following year all dead plants had been removed. This not only eliminated habitat for the birds it probably also (albeit indirectly) lead to the deteriorating health of the surrounding bush. By 2014 the copses of wattle had been completely defoliated by insects, a situation probably exacerbated by the absence of the small birds, especially Brown Thornbill that particularly favour foraging on the feathery foliage of bipinnate wattles.
Ten Yellow-rumped Thornbill were recorded at the site in 2006, two in 2007 and 2008, one in 2009, 2010, 2011 and 2012 but none have been seen there since.
It is admirable that landowners are vigilant about the elimination of weeds on their properties. However, in the absence of suitable native vegetation this sometimes provides important habitat for small birds, invertebrates and reptiles. My observations at The Pond well illustrates, albeit at a very small scale, that if you eliminate habitat the birds (and other fauna) are unable to persist. Most birds are not fussy about whether the vegetation is native or weedy – they just need it to be present.
Understorey and Feral Deer
One of the surveys sites on the Cressy property is a fenced area with a conservation covenant. In 2006 when my surveys began Noisy Miner dominated the site and there were few other birds around. This native honeyeater favours areas with no or little understorey and aggressively chases most other birds from its territory. Because the area had been fenced to exclude stock grazing not long before my study began I anticipated that the understorey of orchids and herbaceous and woody plants would recover and the site would no longer be favoured by Noisy Miner. In my first report I recommended (unrealistically given the cost involved) that the bush at the base of nearby foothills be linked to the fragments of native vegetation on the property via natural gullies by fencing off to encourage natural regeneration.
By the second year of the surveys this had effectively happened although not quite as I had envisaged. Rather than a mixture of local provenance trees and shrubs, extensive plantations of shining gum surrounded the search area. This resulted in slightly fewer bird species near the search area the following year because several large old hollow-bearing eucalypts were sacrificed to make way for the plantations thus eliminating nesting sites for Striated Pardalote, Welcome Swallow and Tree Martin. Nevertheless the plantations had the desired effect of overcoming the isolation of this patch of native vegetation. And the fencing also had the desired effect because it allowed the understorey to recover.
In 2012 Yellow Wattlebird, Brown Thornbill, Spotted Pardalote, Grey Fantail and Shining Bronze-cuckoo were recorded in the plantation adjacent to the native bush. But they were not entering the survey site which was still dominated by Noisy Miner. The understorey had not continued to recover as predicted but had deteriorated considerably with all the wattle and eucalypt seedlings and woody shrubs that were flourishing in the early days of the surveys damaged or destroyed by feral deer.
Fallow deer have increased in recent decades and now number approximately 30,000 animals. They were first introduced in 1836 to provide a resource for hunters and were subsequently introduced on a number of occasions in the districts around Interlaken, Ross/Campbelltown and Deddington/Blessington, with satellite populations becoming established throughout the northeast mainly as a result of either escapes or animals being released from unviable deer farms. Culling is limited and there is a strict bag limit with the aim of keeping the resource genetically viable and of good quality for trophy hunters. In 'A Statement of Current Management Practices for Tasmanian Wild Fallow Deer' (Feb 2011) it is stated that 'Landowners can apply to the department for crop protection permits outside the recreational season for deer that are causing damage to crops or pastures'. There is no mention about the widely reported damage to native vegetation on conservation properties where landowners have invested time and money to protect of flora and fauna on their land.
Irrigation, paddock trees & farming practices
As noted above, in 2006 aerially feeding birds were 'in abundance' - as were numerous centuries-old hollow-bearing paddock trees. These trees, essentially irreplaceable in our lifetime, are important for many species because they provide stepping stones in the landscape and numerous nest sites and foraging opportunities on their foliage, trunks and branches. Sadly, many of these trees were felled to make way for the plantation and two enormous dams. These practices are occurring across the rural landscape.
The migratory Dusky Woodswallow, Tree Martin and Satin Flycatcher have also declined or completely disappeared from some sites at the Cressy property and are in very low numbers near Ross. Migratory species that breed in Tasmania are likely to be particularly vulnerable because they are dependent on two completely different habitats, one where they breed and one where they spend the winter.
The White-throated Needletail is a trans-equatorial migrant. It faces habitat alteration in two hemispheres and well illustrates the issues facing all migratory birds.
When we first arrived at Black Sugarloaf in December 1988 I vividly remember my ten year old son excitedly pointing to the hundreds of 'swifts' circling high above our property, occasionally swooping low between the trees with an audible whoosh of their wings. In early 2014 we witnessed another flock behaving in a similar manner, but this time there were only about 30 or 40 birds.
White-throated Needletail (previously known as Spine-tailed Swift) have declined in Australia by approximately 50% since the 1950s. This has partly been attributed to the clearing and/or modification by changed fire and grazing regimes of forests and woodlands in eastern Australia over the past 60 years that cause a reduction in the abundance of invertebrate food and loss of roosting habitat.
The use of insecticides has also decreased the abundance of invertebrates leading to birds foraging over a wider area to fulfill their dietary requirements. Furthermore, the birds may be affected by secondary poisoning by insecticides that accumulate in sub-lethal doses in their prey.
Alteration to their breeding ground, the vast Boreal forests of Siberia, is the main cause of their decline. The clear felling of these Tiaga forests has increased alarmingly with 50% being logged illegally since the break up of the USSR. Over 2,000,000 m³ of timber a year has been taken from the forests with some estimating that the forests will be destroyed in the next 20-30 years. White-throated Needletail nest in solitary hollows in large deciduous or coniferous trees usually at the edge of clearings. The breeding season is brief and the birds must get enough sustenance not only for themselves but also to sustain the rapid growth of their two to seven young.
Fire and urban development
In 2008 'A sound Idea', a project to monitor acoustically Tasmania's bush and forest birds was initiated. More than 90 people made recordings at over 160 locations across Tasmania between and including Tasman Island and King Island, with many participants making seasonal recordings at particular sites. Consequently, we have some idea of the species that are able to persist in areas that have thus far not been surveyed for birds.
The project involved volunteers recording for twenty minutes in their backyard or local bush using a small digital sound recorder. Volunteers needed no bird identification skills but simply the ability to follow instructions and an interest in assisting in a project they felt was worthwhile. The recordings were listened to, a large database of records was amassed and participants received a list of the birds they recorded.
Monitoring projects that rely on volunteers inevitably result in more surveys being conducted in well-populated rather than remote areas. This is one project that has benefitted from such a bias. The recordings indicate that areas close to human habitation, especially bush on the edges or within the boundaries of towns and cities, support many of the native species (Grey Shrike-thrush, Golden Whistler and endemic honeyeaters) that are no longer persisting in some areas of the rural landscape.
Unfortunately for the birds, these areas of bush are likely to be cleared for industrial or residential development and/or subjected to frequent fuel reduction burns. These activities will be at the expense of native wildlife.
Feral cats and European Wasps
The impact of feral cats is difficult to gauge but anecdotal evidence suggests that cat numbers are increasing. A dead Australasian Bittern was found in a garden near St Helens and the evidence indicates that it was carried into the garden when dead and ripped apart. In the same garden, 2 small passerine species were also found dead within a 2 week period after 2 kittens were observed with an adult feral cat. It is speculated that cats could or did kill these birds (Liz Znidersic personal communication).
The article about European Wasps by Sue Gebicki describes the activities of these aggressive insects whose voracious appetite for native invertebrates is likely to be affecting the food supply of many birds.
- Forestry Tasmania Major Eucalypt pests and beneficial insect, version 3, October 2013.
- 4 Farmers Pty Ltd., Alpha-cypermethrin 100 EC, Insecticide safety directions.
- The Examiner, December 30 2009.
- Lindenmayer, D. & Burgman M. (2005) Practical Conservation biology. CSIRO Publishing.
- Stott, C.M. Submission in relation to Forestry Tasmania’s Alpha-cypermethrin derogation application to FSC, Oct 2014.
- Tarburton, MK (2014) 'Status of the White-throated Needletail Hirundapus caudcutus in Australia: evidence for a marked decline'. Australian Field Ornithology Vol 31, 3 September 2014
- The Mercury 23 March 2015