This week at Macquarie Island: 24 February 2017
Time to check on our cape petrel chicks and the Macquarie cushion is getting some attention this season, as well as science interpreted by a carpenter!
Cape petrel nest checks
Cape petrels – or cape pigeon, pintato petrel, cape fulmar – are a common seabird in the southern ocean. They typically breed in colonies on the Antarctic continent, sub–Antarctic and sub–temperate islands.
Their nests are made from small pebbles and are typically located under overhanging rocks, plants or in a crevice. One egg is laid between November and early December. Incubation lasts for about 45 days and then one parent broods the chick for about 10 days until the chick can thermoregulate, at which time both parents can focus on feeding the chick.
This month the ranger and field biology team visited the cape petrel breeding area on North Head to see how their small colony was going. Nests were first located in December, just after they had laid their eggs, and then these nests were revisited this month to see which parents had successfully raised a chick.
On the day of the latest visit the sun was shining and the winds were low: you could say it was almost balmy! The cape petrels have a very specky view from their nests, most of which have morning sun, afternoon shade and 180 degree ocean views! The chicks are getting quite big and some are close to fledging (when they head out to sea to fend for themselves).
The data that has been collected will contribute to the long–term monitoring program run by Tasmanian Parks and Wildlife Service. The results from this year will be incorporated into the database and analysed later this month to assess the population’s status and trends. This information will help inform the management of the cape petrel’s breeding area so that we can ensure the health of the cape petrel population on Macquarie Island into the future.
Searching for refuges – Macquarie cushion
Over the past two and a half months 'Team Azorella' have been climbing peaks, crossing valleys and skirting escarpments on their mission to better understand the patterns of dieback in the Macquarie cushion (Azorella macquariensis).
The Macquarie cushion is the dominant plant across more than half of Macquarie Island, occurring in its highest densities on the exposed plateau. Found nowhere else in the world, the Macquarie cushion is an important part of our ecosystem, creating habitat for other plants and animals and forming a significant part of the iconic terraces that Macquarie Island is famous for.
In 2008/2009 an island wide dieback event was first recorded in the Macquarie cushion, which resulted in the species being listed as critically endangered. Research suggests that the dieback event was primarily driven by stress from a reduction in available water (caused by more variable weather patterns), which has allowed a secondary pathogen event to take hold across the island. This implied that there may be some less exposed areas on the island with lower rates of dieback. Under an Australian Antarctic Science Project (#4312) led by Monash University, the team is on the hunt to identify areas of refuge from dieback across the landscape.
In December 2016 project team members Dr Dana Bergstrom (AAD), Dr Jennie Whinam (UTas) and Cath Dickson (PhD student, Monash) began field work to establish data–loggers (temp. and humidity) across the island. However December was a record weather month, resulting in some very soggy and windy Macca fieldwork days. Fortunately the New Year brought a change in the weather allowing Cath and John Burgess to establish the remaining microclimate data-loggers, take leaf samples and complete plant condition and microtopography assessments at all 62 sites.
The sampling took the team to simply amazing landscapes, whether they were very steep highly exposed slopes, fellfield peaks or gentler grass/moss turf hillsides. The team have enjoyed the challenge of sampling on slopes greater than 45°! Highlights included the rarely visited Azorella special management areas in the south of the island, which contain some of the healthiest Macquarie cushion carpets and terraces.
Dieback was recorded across the island, however, the severity and levels of recovery varied between sites. Cath is looking forward to spending time in the lab with samples and analysing the resultant data in the year ahead. A huge thank you to the whole Macca team who have supported the project either through field work, carrying gear, sourcing or modifying equipment or providing invaluable local advice!
Dissection of a science lesson (or a carpenter’s interpretation)
Occasionally during our time at Macca some folk give a presentation of the work they are doing here, which usually consists of a talk and some photos or a power point presentation. Our latest show was from Prof Murray, who is at Macca conducting atmospheric observations. His talk was about water and ice in the atmosphere and what conditions can create ice build–up on aeroplanes. This sounds like pretty useful information to me.
An instrument Murray installed on Macca is a Polarsonde, which takes readings from clouds and the data is passed on to weather and aviation people. One interesting aspect of the presentation for me was the graph from 1930, which was not only accurate but still referred to today. Quite incredible when you consider that electricity was only commonly used a couple of decades prior. There was a lot more to Murrays presentation than my brief interpretation and he may feel “a right of reply” may be in order for the next issue. Just remember next time you put your sunnies on and see a pattern on your windscreen you are participating in science!
Following the eradication of wekas and feral cats, rabbits and rodents were enjoying the island flora and fauna and living the good life. Rabbits consumed the large, leafy megaherbs and grasses, which lacked the ability to adapt to grazing. Extensive damage was occurring to the tall tussock grassland, resulting in a loss of breeding habitat for nesting seabirds and the destabilisation of slopes. Rats preyed on seabird chicks and eggs, and were a threat to a least nine burrowing seabird species breeding on Macquarie Island.
The presence of rats and mice was also inhibiting plant regeneration. Vegetation communities are a critical part of the Macquarie Island ecosystem as they protect soil and rocks from weathering, stabilise steep slopes and provide habitat for invertebrates and nesting sea-birds.
In 2007, the Australian and Tasmanian Governments jointly funded the Macquarie Island Pest Eradication Project (MIPEP) to the tune of $24.6 million, to implement the plan to eradicate rabbits, rats and mice from the island. This was a massive task and would take years to plan and undertake and needed to be 100% successful.
The first stage of the project was aerial baiting: helicopters were used with bait buckets slung underneath as this was the best method to spread bait evenly over the whole island. Winter was chosen as the preferred time for baiting as this is when most of the wildlife is absent from the island and pest populations are at the lowest point in their annual cycle. Any activity on the island is always subject to the vagaries of the weather: the project started in the winter of 2010 but had to be postponed due to weather until 2011, when they had a successful season and baiting of the whole island was completed by July of that year.
Once baiting was over, the hunters and dog handlers arrived in late July for the next phase of the plan: they had to cover every inch of the island in their search for remaining rabbits, and this had to be done by foot.
Additional field huts were inserted on the island to provide accommodation and these teams spent four weeks rotating through huts and search zones on the island before coming into station for one week for some R&R. There were 13 dogs for this part of the operation and all had been specially trained not to disturb native animals – they undertook a two-stage assessment and certification process to ensure they were fit for the job. Only 13 rabbits were located during 2011, an indication of how successful the baiting had been.
Hunting continued throughout 2012 and in 2013 rodent detection dogs were deployed to the island for 12 months as well, to determine the presence of rats and mice. An estimated 92,000 kilometres was covered by these teams in their thorough crisscrossing of the island.
MIPEP was declared a success in April 2014: not a single live rabbit had been spotted since December 2011, and no sign of mouse or rat since July 2011: total eradication had been achieved.
In order for no new pests to be introduced, strict biosecurity procedures are in place for any people, ships or cargo coming to and from the island, including a full bait line across the isthmus over summer when station traffic increases. Vigilance is required to ensure that the island can return to its indigenous ecosystem, and there are various science projects on the island this summer who are endeavouring to find out what that is, since the pests pre-date accurate scientific records for the island.
The following publications used as sources: “Eradication of Cats (Felis Catus) from subantarctic Macquarie Island” by Susan A. Robinson and Geoffrey R. Copson; “Macquarie Island: from rabbits and rodents to recovery & renewal” Australian Govt – Department of the Environment; “Macquarie Island Pest Eradication Project” Tasmanian Parks & Wildlife Service.