Montague Island Nature Reserve - Seabird Habitat Restoration Project
The construction of the Montague Island Lightstation complex in the late 1800s severely disturbed the island's sandy soils. Unsuccessful attempts were later made to stabilise the soils around the lightstation by spraying the surrounds with tar.
In the early 1900s, lightkeepers sought an alternative. They introduced kikuyu grass (Pennisetum clandestinum) and many other non-native plants to help stabilise the soils and provide stock feed (for dairy cows and goats), as well as for decorative purposes.
A 'useful' plant species becomes a problem
Today, there are about 20 species of non-native plants (weeds) on Montague Island as a result of early European settlement. However, of all the weeds on Montague, kikuyu has been the most invasive, spreading across nearly 40 per cent of the southern section of the island. On parts of the island's southern section, kikuyu infestation has created a monoculture which has effectively 'choked' out all other native plant species.
So what's the big deal?
Over 30,000 shearwaters, crested terns and little penguins nest and breed on Montague Island, making it one of the most significant seabird areas on the east coast of NSW. Little penguins have been recently studied by Charles Sturt University as part of postgraduate and doctorate research. These studies support the fact that the presence and continued spread of kikuyu represents the single greatest threat to seabirds on Montague Island, for the following reasons:
- The spreading kikuyu is displacing and reducing traditional seabird breeding areas on the island.
- Annually, three per cent of the island's entire penguin population of approximately 6000 pairs are fatally strangled or entrapped in the spreading kikuyu biomass.
- During the summer and dry winter months, the fine kikuyu growth on the island dries out and becomes more flammable. At these times, there's a risk that thousands of seabirds can be decimated if wildfire is started by accidental causes or lightning on the island.
- If the spread of kikuyu is not controlled, there is the potential for the vegetation on the southern end of the island to become a monoculture.
Solutions from science…
Over the past decade, Charles Stuart University researchers have been investigating kikuyu management on Montague Island. The research has included:
- mapping the changes in distribution of kikuyu grass, and investigating subsequent changes in little penguin distribution
- monitoring breeding success of little penguins within various habitats
- monitoring the response of both the vegetation (particularly kikuyu grass) and little penguins to various kikuyu treatment methods being trialed.
The research is being used to assist with kikuyu grass control, and to develop a kikuyu eradication plan, while at the same time improving seabird habitat in infested areas of the island.
And the best solutions are?
Research and management have found that no single method applied on its own would be successful in controlling or eradicating kikuyu to the extent required. Based on the current research, the NPWS proposes to carry out a combination of the following:
1. Herbicide spraying
Kikuyu grass will be sprayed with a very diluted form of Round-up (low aquatic toxicity and low irritant Round-up Biactive) in designated zones across the island over a period of six years.
The herbicide will be used initially to kill the existing growth, which will be allowed to dry out. The remaining dead grass will be burnt to remove the metre-deep mass of grass, and further follow-up applications of herbicide will be applied on the regrowth.
When diluted, this herbicide is very effective on kikuyu and has little or no little impact on native plants. Regular follow-up spraying will be required in all zones until the plantings of native vegetation have grown sufficiently to shade out kikuyu.
2. Application of controlled fire
Research and management has found that the fire is important in reducing kikuyu growth, which in some places is over 1 metre deep. Removal of kikuyu by fire provides:
- ease of movement for seabirds previously restricted by dense kikuyu growth, as well as reduced risk of injury or death from entanglements in the plant's runners
- easier and effective access for initial and follow-up ground spraying
- easier access for planting seedlings
- speedier growth of seedlings
- minimal disturbance for penguins, as research has found that fire did not prevent penguins re-nesting quickly within areas that had been burned.
Fire is the most cost-effective method of removing the dense kikuyu growth on the island.
3. Revegetation of the island with native plant species
Dense revegetation is the medium and long-term key to the success of the project. Once established, native plants will:
- provide a suitable habitat structure for little penguins and other seabirds
- 'shade-out' and reduce the reinfestation of kikuyu and other weeds on the island
- reduce erosion within island's fragile soil structure
- reduce and eventually eliminate the need for follow-up herbicide spraying.
4. Provision of temporary artificial nesting boxes
In order to minimise the impact of fire on penguins within the designated management zones on the island, up to 200 artificial nesting boxes will be placed in each zone immediately after burning. These boxes will only be removed after the native vegetation has re-grown and provides suitable habitat for the birds.
Native plant species to be planted in the designated zones of the Montague Island Seabird Habitat Restoration Project
The following native remnant headland species were selected for revegetation of the six management zones. They will be planted at 50-centimetre centres. These species were selected due to their fast-growing nature and ability to 'shade-out' kikuyu.
|Species||Zone 1||Zone 2||Zone 3||Zone 4||Zone 5||Zone 6|
|Allo casuarina verticillata||200||600||600||200||200||600|
|A total of 123,000 plants||9000||31,000||31,000||10,400||10,400||31,000|
How long will all this take?
The project will take six years to complete, commencing June 2004, with one zone per year being treated. Follow-up kikuyu spraying and further planting will take place during the six years, to ensure the zones remain kikuyu-free.
We anticipate that the methods described may be used beyond the six-year project to control and eradicate kikuyu on other parts of the island, right up to the historic lightstation precinct.
Why all this trouble just to get rid of kikuyu?
As part of the state's peak conservation agency, the NPWS simply cannot adopt a 'do-nothing' approach to the kikuyu problem on Montague. This invasive species now affects 40 per cent of this important island nature reserve. Two of the seabird species (shearwaters and crested terns) on Montague Island appear on two international migratory bird agreements to which Australia is signatory (JAMBA and CAMBA).
Science has now proven that without intervention, the presence and continued spread of kikuyu on Montague Island will have disastrous long-term impacts on the island seabird populations. The challenge for the NPWS is to reverse this trend in a manner that has minimal impact on seabirds and provides a satisfactory long-term solution.
To meet this challenge, the Seabird Habitat Restoration Project has been developed, based on sound scientific research. The measures proposed by the project have been carefully considered in a Review of Environmental Factors and through a peer review process .
Who is taking notes on the project's progress?
For the first three years, the project will be the subject of a PhD study that will monitor the overall effect of spraying, fire, and revegetation on seabirds within the seven zones.
The information gained from the study will be not only be used to refine the methods on Montague Island, but can also be applied to similar weed projects on other offshore seabird islands around the Australian coast.
The NPWS will be seeking further assistance from Charles Stuart University beyond the PhD study to continue monitoring the Seabird Habitat Restoration Project.
Does the Seabird Habitat Restoration Project present a risk to seabirds and the island?
Most wildlife management involves some level of risk, especially when wildlife is physically handled or disturbed.
Using fire in areas known to be inhabited by penguins also involves risk. However, as 95 per cent of the penguin population remains at sea between May and July each year, the risk is reduced by conducting the burning in June.
To further minimise the risks, penguin nesting sites in each zone will be located, marked and monitored months before any burning is conducted.
Immediately before a burn, each zone will be carefully searched. Any penguins found will be held in an enclosure for the duration of the burn (approximately 24 hours) and released only when the burn is declared out.
Each burn will be patrolled by firefighters from the time it begins to the time it is declared out. Any penguin attempting to enter the fire ground between those times will also be held within the enclosure until the fire is declared out.
All activities associated with the Seabird Habitat Restoration Project, including the burning, have been subject to a review of environmental factors. The seabird handling, enclosure and release has been peer reviewed and approved by the Charles Sturt University Animal Ethics Committee. The burn operation planning has also been subjected to internal and external peer review.
All penguin searching, handling, enclosing and replacement will be supervised and monitored by Charles Sturt University, and on-site veterinary officer and a representative from WIRES.
- Montague Island Nature Reserve kikuyu management zone map (PDF - 1.1MB)
- To find out more about the Seabird Habitat Restoration Project, contact Ross Constable.
Page last updated: 13 June 2012