Thursday, 19 October 2017

Theme Thirteen: Lucky for Some


I've just returned from Matuwa Indigenous Protected Area in central Western Australia, where a fantastic team of volunteers assisted with my ongoing Goldfields Environmental Management Group-funded research on a breeding 'population' of Walluwurru / Wedge-tailed Eagles. This harsh environment normally has insufficient prey for most of the ~40 pairs of eagles to breed successfully each year, but good rainfall earlier in 2017 resulted in the most productive breeding season recorded since research began in 2012, with an amazing THIRTEEN eaglets hatched! As part of my PhD research, I fitted GPS/Satellite-transmitters to four of these birds, devices that will allow us to track the eagles' first movements away from their outback nests and beyond. I was lucky enough to actually watch the first flight of one of the tagged eagles 'Kapiburor' (a Martu word for 'stormy/rainy day', pictured above), as he launched from his eyrie on his brand new but powerful set of wings...

Kapiburor launches on his maiden flight.

Kapiburor was a lucky find and we managed to fit him with a satellite-transmitter on Friday 13th October, just days before he fledged, before heavy thunderstorm activity set in for the evening. He wasn't the first eagle to be tagged though - five days prior, we were very excited to have located a brood of 'twins' in the neighbouring breeding home range, offspring of our well-known adult male Wedge-tail 'Wallu', who (together with his mate Wurru) was recorded as rearing two chicks successfully for the second time in three years!

This brood of 'twins' Djootabay (left) and her brother Karlbartu was a highlight of the field trip.


Above the fenced enclosure was another nest with a single large eaglet, aged about 9 weeks and almost ready to fly. It was wonderful to spend time on country and visit this site with Martu elders and teenage students from the Wiluna Remote Community School, who chose a very appropriate name for the juvenile. 'Yapu', which means 'rock' in Martu Wangka, was named after a fairly large piece of ironstone which I found on the edge of his eyrie, possibly brought in by the adult eagles after being stuck to a large prey item (such as a young kangaroo or Australian Bustard) which could have had sticky, exposed flesh after being left on the ground for several days after being predated. We have recorded rocks in eagle eyries on a few occasions in the past few years, but these have normally been located on failed nests where eggs have been deserted by hungry females and subsequently predated by other birds such as Black-breasted Buzzards (known to use rocks as egg-breaking tools), and possibly crows.


Yapu was fitted with a satellite-transmitter and returned to his eyrie soon afterwards, and we are anticipating his departing flight with great excitement! It will be amazing to follow his progress from the high nest ridge, down to the plain country where his parents hunt, and far beyond when his juvenile dispersal phase begins.

Yapu, a gorgeous eaglet aged ~9 weeks, was named after a large rock found on his eyrie.


On the final day of fieldwork I went in to check on Djootabay and Karlbartu and was very pleased to find them both with bulging crops, full of freshly killed rabbit and goanna observed on their eyrie.

Female eaglets like Karlbartu (left) are much bigger than males.

This gave me a good opportunity to take photographs of the eagles in the wonderful setting sunlight. Each bird's sex was apparent from its relative head length, with Karlbartu (a female, below left) have a much more elongated cere and exposed bill than Djootabay (a male):


After giving these absolutely stunning birds a 'goodbye and good luck' blessing, I returned to the Matuwa camp to pack up. This was by far the most memorable trip to Martu Country I have been privileged to undertake, being one of high productivity, both for the eagles, my research, and the fabulous friendships forged with more members of the Martu community. As a parting gift for my research and engagement with the locals, I was given a beautiful 'Wantu' - a mat/blanket made by teacher Debbie and teenage girls from Marlu (Red Kangaroo) skin. This fabulous gift brought tears to my eyes and I feel so lucky to be able to work on country with these beautiful people.

The next generation of Walluwurru researchers!

It is always wonderful to spend time with Martu women elders at Matuwa.

Huge thanks to Dani, Ben, Renae and Kristal ('Team Eagle'!) for dedicating so much time and energy to helping with my research, to the Department of Biodiversity, Conservation and Attractions for their ongoing logistical support, and of course, to the traditional Martu elders for endorsing this work to be carried out on their ancient land.

Tuesday, 19 September 2017

Eaglets Growing Fast


It's now the season of Djilba and the beautiful wildlife in the forests surrounding my home in the Perth Hills, including our magnificent Wailitj / Wedge-tailed Eagles, are busy rearing their offspring. This means I'm out and about a lot lately, checking eagle nests and aging eaglets in preparation for the satellite-tagging season, which is almost upon us! Here is a beautiful brood of 'twin' eagles which I photographed earlier this week. Keep your eyes on the sky folks - these birds will be in the air really soon!

Tuesday, 13 June 2017

Long Distance Flyers


We know from research conducted by CSIRO in the in 1960's and 1970's that Wedge-tailed Eagles are capable of making long-distance movements of several hundred kilometres, but this important work was carried out during a time when banding/ringing was the only method available. The recovery rate of banded birds is usually very low (perhaps less than 10 percent), and the path flown between banding and recovery sites is not able to be determined. The satellite-tracking methods used in modern research, however, gives much more detail on eagle movement, and it’s been extremely exciting to follow the journeys of juvenile eagles satellite-tagged last year. The above map shows the movement paths of 4 birds from the Perth Hills: Walyunga (who made it all the way to the Pilbara) in pale red, Kala in yellow, Korung in orange, and Yirrabiddi (who only left her natal territory last week) in deeper red. It also shows in blue the northward journey of Malya, who moved 750 km north of Matuwa during dispersal

 The fifth bird, shown in green, is Kuyurnpa, the first juvenile eagle to be tracked using a GPS/Satellite transmitter, being fitted with this device in 2013. She is now nearly 4 years old, and has continued to move very long distances like those we detected in her early dispersal phase several years ago, frequently travelling the ~400 km between the Fortescue Marsh area and the expansive salt lake system of Lake Carnegie. It is clear from these maps that wedgies can certainly fly!, and Also of interest is the apparent pattern that birds seem to prefer going north - possibly due to cyclonic rainfall activity leading to ample food supply, conditions that may well attract young eagles. More insights about their habitat use at the landscape scale will be revealed as our tracking continues!

Thursday, 25 May 2017

Death by Drone?


Walyunga's PTT showed a cessation in movement last week which saw me drop everything and fly north to Onslow to investigate. After a 200 km drive and a 2 km walk I was sad to find the bird's carcass next to a large bend in the Ashburton River, about 1000 km north of his natal home range. Initial examination showed the PTT to be still securely attached to his back, with no visible signs of injury. Curiously, a recently broken dead branch lay on the ground just in front of Walyunga, and it appeared this may have snapped when the bird launch from the ground in an attempt to reach a low perch. I wondered why. It wasn't until I was back in Onslow that I noticed the eagle appeared to have had several wing feathers missing, and I considered that the bird may have been trying to jump up to a perch and take off, without success.

Back in Perth, I took Walyunga's carcass for closer examination by Murdoch Uni's pathology department, and it was then that we noticed a total of 9 severed flight-feathers: 4 primaries on the right wing, 3 on the left, and 2 retrices (tail-feathers). X-rays also showed the bird had a dislocated knee. Although there was no conclusive evidence to prove whether these injuries occurred before or after death, consideration of this eagle's tracking data helps to paint a probable scenario that lead to his death.

Walyunga's right wing showing four primary feathers cut cleanly off.

The below map shows Walyunga making short movements along a bend in the Ashburton River from 5th - 12th May, something consistent with an eagle that, after moving very large distances, has 'taken a few days rest' at a billabong which may be supporting ample food resources (we've recorded this before with other dispersing juveniles, including Kuyurnpa).


But after 19th May, as the below map shows, movement stopped completely.


It appears that Walyunga may have attacked a drone and in the process of grabbing it with his talons, wrapped both wings and his tail around the moving object (as eagles often do when taking prey), which resulted in several neatly cut feathers. Unable to stay airborne, he crash-landed at the site where I found his body and moved around on foot for over a week, before finally dying of starvation.

While it is always sad to lose birds we are studying, especially in these circumstances, the story this tells is a key reason why I am conducting this research. You can see a few more pictures and read the posts made during my trip to Onslow on my Instagram account. I am extremely grateful to Chevron and, the local folk in Onslow, and Lynwood Veterinary Clinic, all of whom assisted me greatly during this 'wildlife forensics' episode!

Friday, 5 May 2017

Perth to the Pilbara


It's now a month since Walyunga, a beautiful male Wedge-tail from our Perth study area, began his juvenile dispersal period and started flying north. Amazingly this bird decided to maintain this trajectory for the next three weeks, moving between 50 and 200 km per day until he hit the Pilbara coast! By midday on 30th April, Walyunga had arrived at Karratha, 1200km north of the nest on which he hatched. This remarkable journey is the longest continuous distance travelled ever recorded for a Wedge-tailed Eagle, a truly amazing feat considering Walyunga is only 7 months old! It is a similar movement pattern to that of Kuyurnpa, who also reached the Pilbara coast in her first few months of independence, and I suspect the recent wet conditions in this region are an attractant for young eagles seeking areas with high productivity. This is something that will hopefully become clearer as my research continues.


Meanwhile Malya, our single survivor from the Matuwa study site, conducted his first 'prospecting' flight on 6th April, drifting 12km north of his natal territory between 11 am and 3pm, before coming home to roost. Then, on 26th April the 9am flight departed Matuwa and Malya was on board! By sunset this eagle was roosting 140km north, and he continued in this direction for the next few days, reaching Lake Dora near Punmu Community by the end of the month. What amazing distances these eagles are capable of flying! More updates soon!

Tuesday, 11 April 2017

Wallu Untagged


When I checked in on the most recent tracking data yesterday and found Wallu's transmitter showed no movement for 3 days, I was worried. This has in the past meant the transmitter's owner has died, and I dreaded to think of Wallu, our longest-tracked eagle, having lost his life. Given we have just moved into the 'new eagle year', and territorial behaviour will be heightening as the breeding season approaches, it would not be surprising to find a resident adult male killed by a usurper. It was at this time of year, 3 years ago, that our adult female Gidgee was ousted from her home range and later died.

Fortunately, however, this story does not have such an ending! I rang the Matuwa homestead and was delighted to talk to the current caretakers, John and Gail Grenville, who kindly offered to assist by investigating further. I later received an incomplete voice-to-text message on my phone, which said:
"Hi Simon,
We found the tracker lying on the ground but no..."
This was enough info for me to realise what had happened, and that Wallu was not dead, and I rang Matuwa back instantly for more news. When John and Gail reached the GPS coordinates shown on my tracking map, they found his PTT on its side with one part of the harness frayed, causing it to dismount. This is a very interesting discovery, as this initial harness design was a 'permanent' mount, unlike the method used now which is made with a weak link, and I expected it may have lasted much longer. It appears the heat and harsh conditions in the arid zone (along with some encouragement from big, hooked beak!), caused the harness to weaken and eventually break on one of the main straps. So after 3 years and 10 months, the end of an era has arrived, and Wallu is wild and free again! We will check on him later this year during our eagle research trip during the breeding season (Wallu is still identifiable from his leg band), and possibly even catch him to give him a health assessment. Thanks so much to John and Gail for their wonderful help! More updates soon!

Monday, 10 April 2017

Walyunga's Gone


The last satellite-tagged Wailitj is the first to leave home! Walyunga, a late-fledging juvenile wedge-tail that we fitted with a transmitter in December, has made the bold move of 'leaving home', departing his natal home range last Tuesday. After not having moved more than about 4 km during the past 4 months of the post-fledging period, he suddenly flew east and spent the night near Wundowie, 35 km away. Then Walyunga travelled inland via York, turning north to reach Goomalling, then passing Wongan Hills and Dalwallinu as he moved nearly 200 km north of Perth!


Walyunga's dispersal path into the WA Wheatbelt region (click to enlarge).

It is so exciting to have reached the stage where our Perth eagles have begun dispersal, and I'm SO grateful to all who supported the initial crowdfund to pay for 3 of their transmitters. This is the first time the dispersal path of a 'wedgie' from south-west WA has been tracked, so it is very exciting to follow Walyunga's route, and anticipate where he might end up next! Don't forget to follow my Instagram account for the most recent updates of our satellite-tracked eagles!