Tuesday, 18 October 2016

An Arid Year


Experiencing first hand the boom and bust cycles of desert life is one of the most appealing features of conducting research in these amazing ecosystems. While in some years decent rainfall is recorded and wildlife is able to flourish, in others it is quite normal for conditions to be dry for many months at a time. For me, one of the constant thrills of researching eagle ecology is the insight into the environment it provides: eagles are a window into their ecosystem. By examining their nesting efforts in one year, we are virtually able to read the land and determine what local conditions have been like for the previous year.

Having just completed assessing the Matuwa Wallu-wurru / Wedge-tailed Eagle population's breeding activity for 2016, it was evident that the past season had been a dry one indeed. Only three of the 35 breeding pairs (less than 10%) produced chicks, compared to five pairs last year, and five the year before. Such productivity is very low but probably quite normal in the arid zone where these top order predators only thrive in occasional productive years. It is also an indicator that ecosystem productivity was low, because only three territories had enough prey for the resident adults to nest, incubate, hatch and rear chicks. 

A typical Wallu-wurru nest from the 2016 breeding season, being partially lined but with no signs of breeding.
 
The majority of eagle territories contained one nest which had signs of preliminary nesting, being partially or fully lined, but there was no evidence of further breeding activity. Together with the tracking data from our breeding adults, these signs of continued visitation to nests show the long-term attachment to territory that Wedge-tails display, first suggested by CSIRO research in the 1970's. Incidentally we did observe adult pairs perching on their nest, or soaring nearby, and while assessing the 100 or so nests from a helicopter, we were able to get some great views of these magnificent birds in flight.

An adult female Wedge-tailed Eagle banks in front of the chopper. Note the bird's barred primary feathers which suggest she has not quite reached full adult plumage.

Despite most nests being empty, one that we visited did have a large, healthy juvenile aged about 8 weeks. The discovery of this eaglet created an opportunity for what was a definite highlight of this recent trip. Martu Elders (who have kindly continued to endorse this ongoing eagle research on their land) and children from the local Wiluna Remote Community School were on country to take part in educational activities, so a small group visited the nest with us to learn about ringing/banding research.


After hand-catching the eagle on the nest, it was lowered to the floor in a handling bag for processing. I was very fortunate to have Bill Brown, a Wedge-tailed Eagle researcher and experienced raptor handler from Tasmania, volunteering with me to help. His skills in holding the bird and keeping it calm during processing were fantastic and allowed the procedure to go ahead quickly and smoothly. 


The Martu Elders, school teachers and children, and a group of bird-banding researchers led by my friend and colleague Neil Hamilton, all watched on as we explained the process of fitting metal and coloured leg-rings to allow identification of the birds, taking measurements, and the overall implications of this research.

Bill Brown removes the eagle from the handling bag.

Once banding and measuring was complete, the eagle was returned to its nest, where it sat quietly and bobbed down to lay flat on the nest cavity. This behaviour is typical for nestlings that want to remain hidden in low, outback eyries. We then all gathered below the Wallu-wurru nest to take a group photograph, during which time the eagle remained quiet. This gave Rita Cutter (one of the Martu women elders) an idea of a name for the bird: Goonta, which is a Martu word meaning 'shy' or 'quiet'. A perfect fit for this female eagle. 

While walking back to the car, the whole experience began to sink in. It brought tears to my eyes to able to be on country with this land's (and the world's!) oldest indigenous culture, people who have for thousands of years lived in a sustainable relationship with the country out here. What an absolute privilege to have their permission to conduct ongoing work to find out more about these charismatic birds of prey, in what I hope can continue to be a ongoing, collaborate venture to engage with this amazing landscape.


The Kalgoorlie Miner reported a great article on this event, which you can read here. Also, the school children have since created some wonderful videos documenting their experiences while on country. You can view these, as well as a selection of photos, at the school's Facebook page.

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