Friends of Grasslands
supporting native grassy ecosystems
PO Box 440
Macquarie ACT 2614
Development Application 202241244
Construction of a new 132 kV transmission line: Monaro Highway , Hindmarsh Drive & 722 Canberra Ave.
Friends of Grasslands (FOG) is a community group dedicated to the conservation of natural temperate grassy ecosystems in south-eastern Australia. FOG advocates, educates and advises on matters to do with the conservation of native grassy ecosystems, and carries out surveys and other on-ground work. FOG is based in Canberra and its members include professional scientists, landowners, land managers and interested members of the public.
The works are immediately adjacent to one of the nation’s most important remnants of nationally critically endangered grassland, which is known habit of at least six threatened grassland invertebrates and reptiles, including the major habitat of the Canberra Grassland Earless Dragon (CGED). It is also a roosting and important hunting site of the Little Eagle. The proposal could result in three major impacts:
- direct disturbance of habitat and creating conditions for weeds to flourish further in the general area;
- risk of collision of the Little Eagle with power lines; and
- predation of threatened fauna, through kestrels and other birds using the power lines as perches from which to prey on threatened fauna.
The EIS has appropriately considered the impacts of disturbance, weeds and Little Eagle collision. However, the degree and significance of predation likely to result from the proposal are considerably understated. The likely impact warrants consideration of further development options. These include placing the cable underground, particularly adjacent to areas of relatively high CGED density, or placing the wires and poles on the north side or median strip of Canberra Avenue. It is not stated why these options were not addressed in the EIS, but they need serious consideration. While it is good that an existing powerline will be replaced, there is no discussion why this important opportunity to decrease the likely predation of threatened fauna is not being embraced – instead we are getting a replacement of the problem, a problem particularly critical to the CGED where loss of even one individual is significant in relation to its long-term survival.
The Cookanalla grasslands, which the power line would pass on the edge of, are an integral part of one of the largest most diverse natural temperate grasslands remaining in south-eastern Australia. The area below or immediately adjacent to the proposed power line is known habitat of the Canberra Grassland Earless Dragon Tympanocryptis lineata (endangered), Striped Legless Lizard Delma impar (vulnerable), Pink-tailed Worm Lizard Aprasia parapulchella vulnerable), Golden Sun Moth Synemona plana (vulnerable), Perunga Grasshopper Perunga ochracea (vulnerable), Little Eagle Hieraaetus morphnoides (vulnerable) and the highly restricted Canberra Raspy Cricket Cooraboorama canberrae which is the only species in its genus and, although not yet formally recognised as threatened, meets EPBC and ACT listing criteria.
Cookanalla is a major habitat of the CGED, which is only known from Majura and the Jerrabomberra Valleys. The species has one of the smallest known geographic ranges of any Australian reptile. All remaining populations are critical for the species survival. The species has undergone rapid and recent decline, thus increasing the risk of extinction. Total numbers are estimated as being in the low hundreds. Any loss of an individual is of significance.
Predation – why the EIS has understated the impact
P 54 (of ecological assessment appendix N): “The meta-analysis demonstrates that raptor predation on threatened lizards is highly unlikely, given hunting from powerlines does not align with typical raptor hunting behaviour, and within the Canberra region, raptors have not predated on the GED, where reptiles have on average accounted for 2.9% of prey items.”
This statement is not correct. There are examples in the international literature of power lines benefiting raptors by providing enhanced perch sites for hunting (e.g. Shrubb 1982; Olendorff et al. 1981; Stahlecker, D. W. 1978). In fact, it has been demonstrated in some studies that the abundance of raptors increases after power lines are established (Stahlecker 1978). Olendorff et al. (1981) suggested that one reason why power line structures are selected as perch sites for raptors is because the elevated position provides an expansive view of the surrounding terrain. Lammers et al. (2007) note that such increases in raptor populations due to newly established power lines is a cause of concern in certain areas where increased predation threatens other species, including threatened species.
In addition, Nankeen Kestrels are often seen perching and hunting from power lines in the Canberra region. For example see Canberra Nature Map records:
The scope of the Canberra Nature Map images of Kestrel’s perched on power lines highlights the erroneousness of the claims in the EIS.
It is also relevant that predation by the American Kestrel Falco sparverius contributed to the local extinction of the endangered Fringe-toed Lizard Uma inornata, but only in patches where they could launch hunting sorties from palm trees. The lizard survived in patches that lack hunting perches (Barrows and Allen 2007).
P54: “Generalist passerines display a preference for abundant and easily attained food sources and are unlikely to successfully predate on the threatened lizard species. Although generalist species are attracted to human activity and disturbance, they hunt with strategies not likely to be successful in capturing an elusive and cryptic reptile that spends most of its time underground or that can readily retreat underground. Furthermore, generalist species typically express a cautiousness that would allow ample time for elusive lizards to escape. “
This unsupported statement wrongly implies that generalist passerines would not be attracted to the new power lines and would not successfully prey on small lizards. Magpies, Ravens, Kookaburra’s, Grey Butcherbirds and Pied Currawongs have all regularly been observed perching and hunting from power lines in the Canberra area and within the grasslands of the Jerrabomberra Valley. Friends of Grasslands member Dr Michael Mulvaney recently observed a magpie hunting from the existing power lines at Cookanalla. All these birds include small reptiles in their diet and would also prey on the threatened invertebrates spotted from their perch. Movement is likely to be the key trigger and these species are unlikely to ignore movement by one of the areas threatened reptiles or invertebrates if they were in their line of site. Magpies, Ravens, Kookaburras and Grey Butcherbird were all considered potential predators of the gecko Gehyra versicolour after they attacked plastic models in an experiment that concluded that reptiles on the edge of habitat patches were at particular risk from predation (Hansen et al 2018). Anderson and Burgin (2008) found a similar conclusion re small skink bird predation in woodland on the edge of Sydney. Thus, there is evidence to suggest that the route of the power line may be an area of high bird predation, and that threatened species would be at risk from birds that hunt from powerlines.
The Canberra Grassland Earless Dragon Action Plan includes within the identified threats to the species the creation of artificial perches for birds such as magpies, ravens and raptors (ACT Parks and Conservation Service 2015). The proponent has inadequately explained why their conclusions are at variance with the Plan.
P 54: “This is reflected in diet composition studies of raptors residing in the Canberra region which demonstrate that reptiles contribute a negligible portion to the diet of raptors.”
This statement is not true for all of the ACT raptors. As indicated in Table A.1 (diet composition) in the Environmental Report, reptiles comprised between 0.1% and 87% of the diet of Nankeen Kestrels (in three of the five studies reported at least 10% of the diet consisted of reptiles). This is not surprising and Frith (1976) notes that kestrels often catch small skinks and dragon lizards. In the ACT, there are unpublished records of predation by kestrels on small lizards including legless lizards (W. Osborne personal observation; J. Olsen pers. comm.). In one recent unpublished case, photographs taken of nesting kestrels in the Majura Valley have shown that kestrels regularly feed small reptiles to their young and that some of these prey items are legless lizards (including striped legless lizards) (see Canberra Nature Map Record https://canberra.naturemapr.org/sightings/4403221).
It is therefore highly likely that they would also prey on Grassland Earless Dragons. This possibility should not have been played down in the report and instead should have been given further consideration.
Lizard predation may also vary depending on seasonal changes. In 2020 lizards only accounted for 3.3% of the Little Eagle diet but in 2017 it was at 16.5%. The variance was thought to be because of the relatively high rainfall and vegetation growth: in 2020, eagles could not see or catch lizards concealed by tall ground layer, or perhaps reptiles were less active in cooler rainy conditions (Rae et al 2021). Thus the predation risk faced by threatened lizards will vary from year to year and in certain years can be very high.
P 60. "Populations of GED adjacent to the alignment include very few individuals (Biosis Research 2012)."
This is not true. A high density site for GED occurs on the Cookanalla property within 30 metres of Canberra Avenue. In preparing the Environmental Report further information should have been sought from the ACT Government and this would have confirmed that a critically important key population of grassland earless dragons occurs at this location (in the adjacent Cookanalla property between poles 19 and 20 and near pole 21).
Alternative prey hypothesis - Appendix A
“GEDs are not easy to catch, roughly scaled and bony, and in low abundance.”
This is a poorly informed suggestion. It is not supported in the report by reference to suitable evidence. Grassland Earless Dragons are in fact comparatively slow-moving and cannot rapidly move through grass tussocks like legless lizards and other more stream-lined species. The point about being roughly-scaled and bony is an ignorant statement – GED in fact are softer-bodied and more delicate than many of the species of reptiles taken by raptors.
Further consideration of alternatives is warranted
Given that the power line will be a hunting perch of various bird species known to consume reptiles and invertebrates, significant impact on the CGED is probable and significant impact on most of the other threatened reptiles and invertebrates remains likely. The proposal should not be approved in its current form. Alternative such as burying the power line, burying part of the power line where it abuts CGED habitat or placing the poles on the north side of Canberra Avenue or northern part of the median strip should be investigated.
Conditions proposed in the application to minimise impacts should be applied to a revised route. The following measures are particularly important.
P61: “Key to avoidance of potential impact during construction, would be undertaking works when the species are not active. Measures to be implemented include: –Construction of poles along Canberra Avenue will be programmed to occur between April and October, when the species is less active….”
P61: “In addition, in order to modify perching behaviour of predatory bird species, perch guards are to be installed on the poles so that avifauna are unable to perch on the top of them and potentially predate on threatened species from them.”
Little Eagle considerations
The proposed deflectors and spacing between lines probably means that the risk of Little Eagle collisions has been appropriately minimised. It is important that the Little Eagle Research Group be in agreement with any final designs and that they be consulted re investigation of alternative pole routes.
Direct disturbance and weed control
Disturbance associated with the works will increase presence of weeds, particularly African Lovegrass, which could lead to increased invasion pressure onto neighbouring grassland. It is important that the Weed Management Plan includes (a) minimisation of disturbance during works (e.g. avoiding work in wet conditions and maintaining vehicle hygiene) and (b) long term commitment to returning disturbed areas to a ground cover dominated by perennial native grass species.
As described in the report each pole will require access to the work area by bore lifter machines, concrete trucks, pumps, excavators and cranes. Such work and vehicle movements should not impinge beyond existing road easements.
Professor Jamie Pittock
21 March 2023
ACT Parks and Conservation Service (2015) Grassland Earless Dragon (Tympanocryptis pinguicolla) Action Plan. (Note recent genetic work saw the ACT populations of this species becoming a species in their own right (T. lineata), but the Action Plan was directed towards only the ACT populations).
Anderson, L., Burgin, S. Patterns of bird predation on reptiles in small woodland remnant edges in peri-urban north-western Sydney, Australia. Landscape Ecology 23, 1039–1047 (2008).
Barrows, C. W., & Allen, M. F. (2007). Persistence and local extinctions of endangered lizard Uma inornata on isolated habitat patches. Endangered Species Research, 3(1), 61– 68.
Cunningham, S. J., Madden, C. F., Barnard, P., & Amar, A. (2016). Electric crows: powerlines, climate change and the emergence of a native invader. Diversity and Distributions, 22(1), 17-29.
Frith, H.J. (1976). Birds in the Australian High Country. Second edition. Reed, Sydney
Hansen N. A., Sato C. F., Michael D. R., Lindenmayer D.B. and Driscoll D.A. (2018) Predation risk for reptiles is highest at remnant edges in agricultural landscapes. Journal of Applied Ecology 56:1.
Lammers, W. M., & Collopy, M. W. (2007). Effectiveness of avian predator perch deterrents on electric transmission lines. Journal of Wildlife Management, 71(8), 2752-2758.
Olendorf, R.R., Miller, A.D. and Lehman, R.N/ 1981. Suggested practices for raptor protection on power- lines--the state-of-the-art in 1981. Raptor Res. Rep. No. 4, Washington, DC U.S.A)
Rae, S., Mulvaney, M., Wimpenny, C., Brawata R., Stohl. J., Davies, M., Roberts, D. & Olsen, P. (2021) Breeding Success and diet of Little Eagles in the Act and Nearby NSW in 2020. Canberra Bird Notes 46(1): 57-63.
Shrubb, M. (1982) The hunting behaviour of some farmland Kestrels, BirdStudy, 29:2, 121-128, DOI: 10.1080/00063658209476746
Stahlecker, D. W. 1978. Effect of a new transmission line on wintering prairie raptors. Condor 80:444-446.