930 Days... then One Day Off

 
In the two and a half years we have spent keeping a detailed eye on Wallu's movements, he has not left the fixed and precisely bounded piece of Matuwa that comprises his home range. Despite occasional daily wanderings of up to 60 km, Wallu has for more than 900 consecutive days roosted at home. Today we recorded a break in that trend - Wallu decided to wander ~35 km east and spend the night in a small patch of trees alongside a creek-line half way between the Matuwa boundary and the Gunbarrel Highway. This spot is shown by the eastern-most red dot on the above map (click to enlarge). The next day he was back home again, ending the next few days at well-used roost sites. Are his two daughters Djentu and Minyma still in Wallu and Wurru's territory? I would love to know!

So what are all the green dots!? You might remember from previous posts (scroll down) that green is the colour I've used for our two-and-a-half-year-old girl Kuyurnpa. Her behaviour continues to be very interesting, with the contraction back towards her natal territory observed in the past few weeks carrying on. As you can see on the above map, which shows the past month of tracking data, Kuyurnpa has actually roosted on Matuwa for two nights (she even saw the New Year in just 10 km north of her natal territory!), and continues to regularly wander between the property and the neighbouring Wongawol and Carnegie stations to the east and north. This behaviour is almost identical to that observed for a young male Spanish Golden Eagle (Aquila chrysaetos), who contracted his wanderings back to within 20 km of his natal nest in his third year. I am so curious and excited about what Kuyurnpa will do in the next 12 months - will she settle down and breed? Let's keep tracking to find out!

Further Down the Track

It's been a very busy past couple of months in the eagle tracking world, with the 'Where Do Wedgies Dare?' crowdfunding campaign taking up much of my time... but the good news is, the time I spent marketing paid off, and the campaign was successfully funded! This means a couple more eagles are set to be tracked in the New Year! As 2015 comes to a close, I can hardly believe it's been two-and-a-half years since this project began. The data gather so far has given us incredible insights into the Wedge-tailed Eagle's ecology, and as I prepare to (officially) commence my PhD at Murdoch University in 2016, there are no doubt even more exciting discoveries awaiting us! :-D

So, what has been happening in the lives of Wallu and Kururnpa?

Ladies first! If you've been following this blog closely, you might remember that, in October, our young girl returned from a long stint at her 'second home' at Roy Hill Station and was last recorded back in the vicinity of Lake Carnegie. Information from the WA Department of Agriculture and Food's Feral Herbivore Eradication team, who have regularly flown over this area in recent months, reveals there are several sites at Carnegie with surface water present, and many other Wedge-tails of various ages were recorded at this location. This explains why Kuyurnpa is spending time here: surface water means food, and other eagles means friends (birds of a feather flock together)! Similar patterns of young, non-breeding eagles 'living together' have been observed in the Golden Eagle (Aquila chrysaetos) by my Scottish pal Ewan Weston.

The above map shows Kuyurnpa's tracking data for the months of October and November. Interestingly, she flew across the north-eastern corner of Matuwa in late October, then actually came in and roosted less than 10 km from her natal nest on Matwua on 9th December. After a brief overnight stop, she winged her way a lazy 120 km east to roost north of Lake Carnegie again. (Remember you can click these maps to view large images).

Then her interest in her birthplace seemed to strengthen. A week later, Kuyu flew over her natal territory (shown approximately by the blue triangle) around 2 pm, drifting back to Wongawol Station (the easterly neighbour of Matuwa) to roost:
 

Kuyurnpa's roosted on Wongawol Station on 16th December 2015.

The next day (17th December), Kuyurnpa drifted south-west back onto Matuwa, and at 9 am was soaring at 1800 m above Lindsay Gordon Lagoon, less than 2 km south of Wallu's home range. By nightfall, after another day of floating high above the red dirt, she was roosting just 11 km south-east of her previous night's roost:

Kuyurnpa's roost on 17th December is shown by the green dot in the centre of this map (click to enlarge).

Kuyurnpa flew south and east on 18th December, then, keen for some more time on Matuwa, she headed north-west and spent the night of 19th December in a patch of tall Gidgee (Acacia pruinocarpa) trees not far north of the Lorna Glen homestead. This roost site was in the middle of four active breeding territories on Matuwa:

On 20th December, it was time for our girl to head back to Carnegie. This map shows the latest few days of tracking data, with all roosts being either on Wongawol or Carnegie. 

You can 'watch' a slideshow of consecutive days showing Kuyurnpa's travels by clicking the first map and scrolling through to see additional points from each day.

What will the next week of tracking data show? Will this trend of homeward wanderings continue?

Now... what of Wallu?

Wallu's tracking data for the past month, showing most roost sites near his nest, and the nearby rabbit warren.

Having two large daughters to feed has no doubt kept him and mate Wurru very busy! Djentu and Minyma, which were photographed, colour-ringed and named in October, are now well and truly into their post-fledging period. I would love to have satellite-tagged them in October and be closely following their progress, but unfortunately we can only assume they are safe and well, and hope for a re-sighting of their '006' or '007' colour-rings one day in the future. Although the rain season should be approaching with the coming summer period, less than 30 mm has fallen at Matuwa in the past two months, meaning food could well be in short supply. Increasing daily temperatures, which we already know can kill juvenile eagles in the arid zone (see this post for more information), also add to the challenges these young birds face, and will no doubt claim more juvenile lives this season. Unless these birds are marked in some way, many of these deaths will go undetected, leaving us with little knowledge of the impact (positive or negative) to the Wedge-tail population.

As you can see in the above map, Wallu has remained focused around his 2015 nest site, with regular (almost daily) visits to one of the key rabbit warren hunting sites. Interestingly, though, we did record another short 'Wallu Walkabout', similar to the one recorded in January 2014, in the past five days:

On 18th and 19th December, Wallu's 9 am and midday GPS fixes showed him to be 12 and 17 km (respectively) south-east of his home-range. For an adult breeding eagle that we consider to be 'sedentary', the reasons for these forays are a mystery, but new research will always pose further questions, some of which we may never know the answer to. Perhaps more eagle tracking will help us find out!

Crowdfunding Round 2

The second round of Crowdfunding which aims to raise money for TWO MORE GPS/Satellite transmitters, ends in only SEVEN DAYS! If you or anyone you know of are willing and able to contribute, please spread the word about this campaign:


Wedgie Tracking - pozible.com/wedgietracking from Simon Cherriman on Vimeo.

Nest Cam: Inside Wallu's Eyrie

Djentu & Minyma from Simon Cherriman on Vimeo.

During my recent research stint at Matuwa, I placed a motion-sensing camera on Wallu and Wurru's nest, as a way of monitoring Djentu and Minyma's behaviour after they had been colour-ringed. Here are some of the interesting insights gained from the motion camera. Enjoy!

Djentu and Minyma

Yesterday I had the privilege of spending some time on country with three local Aboriginal girls from Wiluna, whose teachers Chris and Anni had arranged a school adventure to enable students to learn about researching Wallu-wurru (Wedge-tailed Eagle) ecology at Matuwa. I began by drawing in the sand a story about our tagged adult male wedgie Wallu, showing his home-range and nest sites, and described the successful nest I'd visited last week. We then set off into the bush to check Wallu's nest, in the hope we would get some nice views of his two daughters.

When we reached the nest tree, I was very happy to spend time showing everyone the evidence used to determine that an eagle nest is active - lots of 'whitewash' (scats), fresh eucalypt sprigs dropped from the nest cavity's lining, and the remains of prey items delivered in the past few days. I climbed the nest to check on the juvenile eagles' progress, and was pleased to see them both standing tall on their sturdy legs, with the blue colour rings showing nicely. 

It was a marvelous view looking down from the nest tree and seeing the students and their teachers talking happily :)

When I descended to show the group close-up photos, the students asked if the two eagle chicks had names, to which I replied "No, we haven't given them any." Then something amazing happened: the girls said "Can we give them names?" This excited me greatly and I of course agreed. After a short discussion, the girls decided on 'Djentu' (pronounced 'jen-doo', which means 'sun') for the older chick, and 'minyma' ('min-muh') which is a local Martu translation for 'girl'.

Djentu (left) and Minyma stand proud and tall on their parents' Wallu and Wurru's eyrie. These two juvenile eagles are now about 10 weeks old and are about 2 weeks away from fledging.

Although they are not being satellite-tracked, Djentu and Minyma still have unique identification numbers on their colour rings, so provided these can be read if the birds are resighted, we will be able to determine who is who!

The bulge in Minyma's neck indicates a full crop, an encouraging sign of a recent feed.

Naming ceremony complete, it was then time to walk back to the car, with special thoughts of the eagles' new names in mind, and a magic outback sunset to look back at.
 

'Twin' Girls!

After a short walk through the Mulga scrub today, I was super excited to spy Wallu perched at the top of a tall Cue York Gum, watching my every move. He stayed for only a few minutes, just long enough for me to snap the above photo, before launching and flapping away with large wing-beats, his PTT aerial waving in the wind. As I had suspected earlier this year, Wallu and Wurru had constructed a new nest, which I spied close to Wallu's perch tree, built 10 m up in another Cue York Gum.

Well hidden among the foliage of a Cue York Gum, Wallu and Wurru's new nest is only the fourth of over 90 wedge-tail nests built in this tree species at the Matuwa/Lorna Glen study site.

My prediction was that Wallu's regular visits to the nest site recorded by our tracking data over the past 2 months indicated that a chick had hatched and continued to be fed on a daily basis. It was most exciting to discover that this also proved to be true, and a split second after spying the nest, I noticed an eaglet standing on it, looking large and healthy. Climbing the nest, however, gave me an even better surprise: not one, but TWO large, healthy eagle chicks!

Two large female eaglets, aged about 8 weeks old.

As part of my research on the movements of juvenile eagles from Matuwa, individuals are being ringed with blue leg-rings (you can read about the first year of conducting such research in 2014 here). The 'twins' from Wallu's nest were lowered to the ground in a handling bag, then removed and held for processing. Even at this age, eaglets have powerful talons which can inflict severe wounds to a human, so care is always taken to hold the birds firmly but gently, ensuring no injuries are sustained to them or the handler.

Removing one of the juvenile eagles from the handling bag - feet first!

       

                                                                                                                      Taking measurements from the eaglets: the tarsal length (left), and rear talon (right).

After data on their morphometrics such as weight, wing length, tarsal (lower leg) length and size of the rear talon were taken, two leg rings (a blue, numbered colour-ring, and a stainless steel ring from the Australian Bird and Bat Banding Scheme) were fitted to the birds' tarsi (all ringing is conducted under appropriate licenses from State and Federal Government authorities). The blue colour rings are unique to this study site, so we know that any eagles bearing a ring of this colour that are subsequently sighted elsewhere in Australia originated from Matuwa/Lorna Glen. As we've seen from Kuyurnpa's amazing travels, eagles can move thousands of kilometres in their first year, so no matter where you are in Australia, keep your eyes peeled!

      

Holding an eaglet firmly by the tarsi and tucking up the wings prevents it from causing any injuries to itself or the researcher (left). The blue colour-rings have a unique number which identify the individual birds (click images to enlarge).

It was encouraging to record both juvenile eagles were large females, each weighing over 3 kg! And at eight-weeks of age, they still have some mass to put on, so will probably have fledging weights much greater than their father Wallu (male eagles are smaller than females, weighing about 3 kg at the most, with females occasionally exceeding 5 kg).

When the processing was complete, the 'twins' were returned to the shady canopy and replaced on their nest.

These juvenile eagles are the first record of a brood of two surviving to near-fledging age in four years of research on more than 30 resident breeding wedgie pairs at this study site. Due to an overall low food supply, most pairs rear 0 young per year, and a maximum of 5 pairs have reared 1 young each in previous years. Such findings are typical for long-lived raptors and are consistent with previous research on this Australian eagle species in arid parts of its range, where rainfall is erratic. Perhaps having satellite tracking devices on eagles increases their breeding success!?! ;-) Well done Wallu, on a fantastically successful breeding season in 2015!

Tracking Well

We didn't have much to report on our two satellite-tagged wedgies Wallu and Kuyurnpa during most of September - both stuck to a fairly similar pattern in their behaviour as previously recorded, with Wallu still tending his (apparently) successful nest site regularly, and Kuyurnpa drifting back up to Roy Hill again and spending most of the month there. Towards the end of the month though, our girl appeared to get itchy talons again and on 20th September embarked on a 1300km desert wander which saw her pass over the Matuwa homestead and continue further south-west than she has ever previously ventured! Today's latest waypoints show Kuyurnpa has again revisited the familiar ground on the north-western side of Lake Carnegie. This journey is shown on the above map (click to enlarge).

Here is a map of Wallu's past month of regular visits to the nest site (large cluster of red dots centre right), and the nearby rabbit warren (smaller cluster to the south-west of the nest). This week I will be heading to Lorna Glen to carry out more research on the breeding and diet of this eagle population during 2015, which will include a check on Wallu's nest. Watch this space for a few more regular updates!