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!

Friday, 24 February 2017

Australian Icons

While in Tasmania recently, I was very excited to receive a phonecall from my friend and expert wildlife journalist Vicki Laurie, who was keen to hear the latest news about my eagle-tracking research. My mind raced back to the above scene from October when I captured a photo of Malya's mother delivering a freshly killed goanna to feed her month-old chick, and we had a great chat about the most recently satellite-tagged Matuwa wedgies, and the findings from last season's research, whose current prime sponsor is the awesome Goldfield's Environmental Management Group (GEMG). Today the wonderful article that Vicki produced was printed in The Australian newspaper, and it was very exciting to see our Malya making his star appearance!

You can click the image below to enlarge and read the full article, or view the online version here. And if you are new to the eagle-tracking world, don't forget to zip back in time to read about the day we sat-tagged Malya.

If you are keen to read more of Vicki's wonderful wildlife writing, I thoroughly recommend her most recent book "The South-west: Australia's Biodiversity Hotspot," which you can find at the University of Western Australia's website.

Monday, 20 February 2017

Phase Three

Our most recently satellite-tagged Walluwurru Malya has continued to spread his wings and now appears to be ranging over most of his parents' territory, which, as you saw last time, is the 'neighbouring property' of our beautiful adult male Wallu. These two eagle territories are shown in red and blue on the above map. During the last few weeks, our 'teenage' wanderer Kuyurnpa drifted in from the east, homing in on a long-range (~300 km) exploratory loop to spend a single night roosting at Matuwa. This creates an exciting opportunity to summarise our three arid-zone eagles currently being satellite-tracked:

  • Wallu, a ~10 year-old mature adult who remains sedentary in a fixed home range, where he has stayed for 3.5+ years;
  • Kuyurnpa, a 4th year immature who is still in her dispersal/wandering phase, moving freely through the arid interior with occasional 'return visits' to her natal territory;
  • Malya, a 1st year juvenile currently still in the post-fledging period in his natal territory, where he will be dependent on his parents until the dispersal phase begins in several months.

These birds represent the three different stages a Wedge-tailed Eagle's undergoes during its life, and it is exciting to be monitoring one arid-born eagle from each stage! I am super excited to know when Malya will begin dispersal, and when (if!?) Kuyurnpa will settle in a breeding territory. Let's keep on tracking and find out!

Sunday, 5 February 2017

Spread those Wings

It is now almost 2 months since Malya fledged, and his progress has been amazing! Initial movements of 50 - 100 m from the nest (shown by the pink pin on the above map) continued over the first fortnight, and soon the young male eagle was roosting in a tall tree just over 1 km from the eyrie (which, coincidentally, I had climbed the day of his tagging, to photograph an oncoming thunderstorm!).

These short bursts were rapidly replaced by longer flights of over 100 m, and in the last month of tracking, Malya has spread his wings widely and travelled across an area with a radius of just over 6 km. He has also been recorded soaring to great heights, reaching altitudes of over 2000 m on some of the warmer days.

Malya's parents' territory happens to be adjacent to that of Wallu, our 'founding member' of the eagle tracking family, and zooming out provides a comparison of the 2 birds' movements during the past 8 weeks. The dark, diagonal line shown on the below map (click to enlarge) is a ridge running north-west to south-east, a landform which appears to form the northern boundary of Wallu's territory. So far these two birds have not overlapped, but it is important to keep in mind a juvenile like Malya may be tolerated 'intruding' on another adult's patch, unlike one of his parents. It is great to be able to have this context of two arid-zone wedgies

Friday, 16 December 2016

RIP Goonta

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.