Friday, 16 December 2016
I write this with mixed feelings - still thrilled with the addition of a second sat-tagged eagle to the eagle tracking project, but saddened by the bad news that was confirmed today. Bruce and Kaye Withnell, the caretakers at Matuwa, rang me to confirm that Goonta was recovered dead, found lying on her side in an open patch of spinifex shrubland, not far from her natal nest. This juvenile wedge-tail fledged only a month ago and had started to make longer movements away from her nest, as anticipated. At this stage we have no idea what the cause of death was, but fortunately there was no evidence Goonta's PTT had interfered with normal movement, or that the harness had caught on any vegetation. You can see in the above photo her feet are spread open and wings drooped, suggesting she died perched on the ground, probably in a very hot position. Being still dependent on her parents for food, Goonta's death may be an indicator of their capacity to provide prey, or suggest there was a sudden shortage of prey nearby, although the latter reason seems unlikely given this territory overlaps with the fenced enclosure containing a high density of boodies and bandicoots. Whatever the cause of death, the trend of low productivity and high mortality in an arid-zone population, as previous research has shown, seems to be continuing.
*POST SCRIPT. A postmortem carried out by Murdoch University in January 2017 found no conclusive evidence of a cause of death.
Wednesday, 14 December 2016
So far the Wedge-tailed Eagle tracking project has been set entirely on Martu Country, and we have made some wonderful discoveries about the ecology of arid-zone eagles residing in this vast landscape. But my dream to satellite-track Wedge-tails actually began a long time ago and a long way south, on Noongar Country, so since starting research here in the desert, I've been working towards adding a south-west WA site to the project. Commencing a PhD project through Murdoch University in July this year created the opportunity to do just that, and part of my research proposal is to compare the juvenile dispersal behaviour of eagles born at Matuwa with those raised in my homeland, the Perth Hills. Today I'm pleased to announce the Perth region is now officially on the wedgie-tracking map, with the fifth and final (for 2016!) Perth Hills eagle being satellite-tagged. This bird was named 'Walyunga' after the very special National Park in which it was born, an important cultural area for ancient Noongar people on whose land I am privileged to be able to live and work.
|Stuart Broadley holds the eagle while its PTT is attached.|
|Walyunga on his eyrie after satellite-tagging. The PTT aerial is visible protruding from his back.|
I am especially grateful to the volunteers who accompanied me to assist with today's satellite-tagging fieldwork, especially Andrea Williams from the Goldfields Environmental Management Group (GEMG), who currently sponsor field operations for the Matuwa eagle research, and Paul Udinga, the senior Walyunga National Park ranger, who has assisted with monitoring of and access to this nest. Thanks also to Heidi Dougherty from the Shire of Mundaring, Parks and Wildlife volunteer Ken Suckling, and my friend and fellow eagle enthusiast Stuart Broadley from the Philippine Eagle Foundation, for helping make this thrilling afternoon a great success! It was a wonderful day to be out bush!
Walyunga (a male) joins Wailitj (female), Yirrabiddi (female - pictured at the top of this post), Kala (male) and Korung (female), all of whom were tagged as juveniles in October and November this year. You can read more about the individual tagging events pertaining to each bird on my personal iNSiGHT News blog. The below map shows the locations of each of these birds' natal territories, shown from north to south in the order the birds are listed above. We anticipate these juvenile eagles will remain 'at home' for the next 3-4 months, then begin dispersing... somewhere! This will be the first time Wedge-tails from a Mediterranean climate have been tracked during this early phase of their life. Where will these wedgies dare? Keep watching to find out!
Monday, 12 December 2016
After a long drive out from Perth to Matuwa yesterday and a few hours sleep, it was exciting to wake up before sunrise and head out to a Walluwurru / Wedge-tailed Eagle nest that caretaker Bruce Withnell had kindly been keeping an eye on for me. I last visited it during the research trip in October with Martu women and volunteers to band a month-old nestling, pictured above, who had been well fed on a recently caught Paarnka / Yellow-spotted Monitor (Varanus panoptes).
Bruce and I, along with my friend David Ryder who generously provided a vehicle for the trip, and fellow ornithologists Tegan Douglas and Neil Hamilton, got to the nest just as the clouds were turning gold in the morning rays, and we were thrilled to see a large eaglet perched on a branch just above the nest. As I scaled the tree to capture the juvenile eagle, which, as Bruce had reported over the past few weeks, was now fully feathered and close to fledging, it launched and sailed on a short glide to the ground. Neil managed to secure it quickly, and carefully holding the talons, calmly carried it back to below the nest, where we had our get set up.
With Neil holding the bird, I set about attaching a satellite-transmitter to it's back. It is always wonderful seeing juvenile eagles up close, an experience that allows one to observe the detail on their beautiful faces. As with many of the Matuwa-born eagles I've observed in the past 5 years, this one had quite reddish plumage. Some eaglets I've seen in the Perth Hills are similar in colour, while others have quite blonde feathers, particularly on the nape. Such variation is yet another fascinating and intriguing feature of these magnificent birds.
|With PTT sitting perfectly between the shoulder blades, the eagle is ready to be returned to his nest.|
When close to fledging at approximately 80 days of age, it is normally very easy to tell the sex of eagle nestlings, with females being noticeably larger, having a broad footspan and being longer in the skull. However, this bird had a complex combination - it's footspan was tiny and very 'male-sized', but the head appeared to be extremely elongated, like a female. Taking the weight and overall appearance into consideration, my feeling is that this bird is a male, but we will be able to confirm the sex using DNA from the feather sample taken. While this research is primarily focused on movement ecology, we are recording morphometrics of all birds handled, which will also broaden current knowledge of the size variation in eagle nestlings of each sex (most previous research on wedge-tails has focused on full-grown immature or adult birds).
With harness attached, it was time to put the eagle back.
To ensure he did not become unnecessarily spooked by my presence, I descended the tree straight after placing the young eagle gently back on the eyrie, and it was wonderful to watch him confidently hop back up and onto the limb on which he was perching when we arrived.
The next morning, David and I revisited the nest site to check on the newest member of the eagle-tracking family, and found the eyrie was empty. He had fledged! It felt very exciting to know we had tagged this eagle just in time to accompany him on the start of a remarkable journey!
On the way back to Perth, we called in to Wiluna Remote Community School where I was excited to catch up with teacher Debbie and many of the children who came to Matuwa during our research trip back in October. I was keen to give them all an update on the recent tagging adventure, and ask the children if they would like to name the eagle we'd just sat-tagged. After a short talk I left an image of the bird on the screen, and one of the girls instantly said the world 'Malya', which she told me means 'cool' or 'awesome' in Martu. Debbie and the class had a quick chat amongst themselves and with Rita Cutter, a Martu elder, and all agreed this was the perfect name. So, welcome Malya! We are excited to be flying with you, high above Martu Country.
|Celebrating the naming of Malya with Rita Cutter (centre) and children from the Wiluna School.|