Tracking the regent honeyeater in southeast Australia
April 2015 saw the 4th, and largest release of captive bred Regent Honeyeaters (Anthochaera Phrygia) into Chiltern Mt-Pilot National Park, VIC, Australia, and the start of the first field season of my PhD. The captive breeding and release of these birds is a huge collaborative project between BirdLife Australia, Taronga Zoo and The Victorian Government Department of Land, Water and Planning (DELWP).
Regent Honeyeaters are similar in size to a blackbird, and have beautiful distinctive gold and black plumage. They feed on nectar, and depend heavily on the flowering eucalyptus trees, which used to dominate southeastern Australia. However, gold mining and agriculture have seen the loss of 85% of this habitat since the 1850’s1, and numbers of Regent Honeyeaters have declined dramatically.
As a result, the Regent Honeyeater is listed as critically endangered, and has been the focus of a captive breeding and release program at Taronga zoo in Sydney, for over 20 Years. Last year, 77 captive-bred individuals were driven to Box-Ironbark forest on the border of Victoria and New South Wales, where they were kept in holding tents for a few days to acclimatise before being released into the wild.
The day of the release attracted spectators from all over to see this ‘jewel of the forest’ be released. Local news stations and radio channels were present, as well as local residents of Chiltern and surrounds, university students, and the teams from Taronga Zoo, DELWP and Birdlife Australia.
All of the birds had colour-coded bands on each leg, enabling us to identify them individually, and half of the birds were fitted with small radio transmitters to help us track their survival and movements over the following months.
One component of my PhD is to evaluate the efficacy of the captive breeding and release program, and for the first 3 months my daily routine, seven days a week, was as follows: arrange all the equipment (radio receivers/gps/walkie talkies, recording equipment) needed for a day of monitoring and meeting the volunteers at the release site at 08:30.
We would split up into teams of at least two and aim to locate each bird, starting with those wearing transmitters. These birds would inevitably lead us to the other birds, not wearing radio transmitters, which were identified by their coloured bands. In the first few weeks, we were still finding up to 66 birds a day, and all of the birds during the course of the week. Once an individual bird was located, we recorded a GPS location and made detailed notes on their feeding behaviour and ecology.
Occasionally we would lose signal for a particular transmitter, which meant driving to all the high points in the area to scan a wider range in the hope of picking up the bird’s transmitter again.
Unfortunately, on a few occasions we found a transmitter on the ground in a pile of feathers and it was evident that the bird had been predated, most probably by a bird of prey. However, not all lost transmitters signalled disaster; the transmitters are fitted with a backpack style harness, which has a cotton weak point sewn in so that any resistance will cause the harness to break and drop off, and will eventually wear away on its own. We found a few transmitters on the ground, and then later found the bird still alive and well in the canopy, probably relieved to be free of his backpack!
The breeding season
As the Australian winter started to give way to spring, the released birds began thinking about breeding for the first time in the wild. The next stage of my research was to find out what was going on during this critical period. This had never been monitored before for captive bred Regent Honeyeaters, but there was a belief among the recovery team and volunteers that previously released birds hadn’t been very successful in fledging young.
The first thing I needed to do was learn how to climb trees, as Regent Honeyeaters, apparently, like to nest in the tallest trees available, on the outer limbs of the canopy! With the help of Grant Harris, a very experienced arborist, I learnt how to assess the health and integrity of the trees in the forest, and to rig them up safely for me to climb.
We decided to modify security surveillance cameras to capture 24hr footage of the nesting pairs. This meant that I only had to climb each tree once, as all the recording equipment and batteries were kept in a pelican case at the base of the tree, minimising the disturbance to the breeding pair
Where possible, we would climb a tree adjacent to the nesting tree, with the camera attached to a long pole, which was then ratcheted to a branch about 3 meters from the nest. The footage was good enough quality to be able to see the female incubating her eggs, and all the other activity that went on!
The first predation event caught on camera was from a sugar glider (Petaurus breviceps), which landed on the branch where a female Regent honeyeater was incubating a single egg that she had laid just that afternoon.
The second predation event I filmed was very similar, and although this female had been able to fend off a sugar glider the night before, tonight she was attacked by a squirrel glider (Petaurus norfolcensis), a larger relative of the sugar glider. The behaviour was very similar, he chased the female off the nest, then came back to eat the eggs. Unfortunately, these two eggs were due to hatch the next day, so he got a good dinner that night!
Although this footage wasn’t news in terms of glider behaviour; it is well know that these marsupials feed on birds eggs – it did provide valuable new information about the threats to the breeding success of captive bred and released Regent Honeyeaters.
A lucky escape
One pair of birds, after losing their first egg to an unknown predator before we set our camera up, decided on a bold new nesting strategy. Instead of building their nest high up in the canopy, this pair decided a one-meter-high dead tree stump would be a safer place! We named this nest ‘Stumpy’ and no one had any faith in its success as it was vulnerable to every predator, from foxes and cats to marsupials such as antechinus (Antechinus flavipes), and the tuan (Phascogale tapoatafa). However, soon two eggs were laid and successfully incubated for 14 days and finally two chicks hatched!
On the morning they were due to fledge, a regular volunteer and I went to check on them and found an empty nest. We assumed they had fledged already, but the parents were still taking food to the nest, which immediately rang alarm bells. We checked the footage and just 5 minutes before we arrived, the chicks were still in the nest.
Two Magpies had attacked the chicks on their very last day as nestlings.
Then the male of the pair made a call we didn’t recognise, and we realised he had found one of his chicks hiding at the bottom of a tree! Named ‘Lucky’, he was the first known wild chick born to captive released birds, and he stayed with his parents well into the summer.
My first field season, which was only initially meant to be three months, ended in the Australian summer after nine months of post-release monitoring.
Reintroductions are becoming an increasingly popular tool for threatened species management as well as broader scale restoration projects. To be successful, these programmes require a series of important decisions to be made, from planning and implementation, through post-release establishment and persistence of populations.
Throughout my PhD I will use decision aid tools, such as Structured Decision Making, to evaluate and inform the discipline of reintroduction biology using the Regent Honeyeater as a case study. I aim to analyse the short-term survival of the released Regent Honeyeaters, using data from the past four releases to investigate whether post-release survival is influenced by the age or sex distribution of released individuals.
Overall, my PhD intends to promote the application of formal decision tools to threatened species management, and showcase how this can reduce uncertainty and support decision-making for reintroduction biology.
1. Mac Nally, R., Soderquist, T.R. & Tzaros, C., 2000. The conservation value of mesic gullies in dry forest landscapes: Avian assemblages in the box-ironbark ecosystem of southern Australia. Biological Conservation, 93, pp.293–302.