Saturday, 3 May 2014

Adult Eagle Update



It's been a while since you've heard anything from our adult eagles - the last update on Gidjee was nearly a month ago, and we haven't checked in on Wallu since early January. What has happened to our pioneering, PTT-bearing predators?

The above picture (click to enlarge) shows what it's like to be a few hundred metres above the ground on the border of Wallu and Wurru's home range, and that of their neighbours to the south. This photo was taken from a helicopter last year. The below screen capture shows what it's like to be Wallu at 3pm today: here, he's a mere 4000 m above sea level! I haven't written about our eagles' altitude data lately, but they are continuing to soar very high and give readings of up to 6000m asl, which provide evidence that the first seemingly unbelievable height of ~6500 m asl that Gidjee reached some months back was indeed accurate.




Spatially, Wallu is very much doing the same thing as he has for the past 11 months. Other than his walkabout in January, the beautiful breakaway country and woodland to the north and west of Lindsay Gordon Lagoon have clearly been too good to leave, and his movements have been restricted to 'prey hotspots' within this area. A wet start to the year has almost certainly helped with prey animal abundance, and it's highly likely that many waterbirds have been attracted to flooding of the two lagoons in Wallu's territory.

Interestingly, there seems to have been a shift in Wallu's key roosting sites in relation to two sections of lagoon (let's call them East Lake and West Lake - see the below maps). When we first tracked him last year, he showed a definite preference for the eastern edge of East Lake, and some scouting revealed that a well-used rabbit warren was probably the reason. Since the rain at the start of this year, Wallu has been recorded frequenting the whole northern shore of West Lake, which might well be due to an increase in rabbit numbers following rain, and the arrival of some tasty ducks and swans! A combination of both is quite likely.

Here's a map showing the large 'ring' of Wallu's favourite locations: the northern shore of West Lake (green circle), and the small cluster of points at the rabbit warren on the eastern edge of East Lake (black arrow). Click on the map to enlarge.



What about Gidjee? The sighting of her perched with Mulga about a month ago was very pleasing indeed, and you would think that not much could change in only a few weeks. However, every day is a new day, and one must never assume.

Gidjee has unfortunately gone missing. The day after her sighting, she unexpectedly left Lorna Glen and headed north-west, travelling 80 km in the three hours between 10am and 1pm. By that evening, she roosted 130 km from her territory, and I was hoping she'd return home the following day. But for the next 3 days, she wandered around this area, soaring and often spending quite some time at altitudes between 1000 and 2000 m. On the afternoon of 11th April she made another long flight north, settling to roost near a large clay-pan (which probably has water in it after such a good season).

The next day she left this roost at 8am, and flew 700 m to land, presumably to perch in a tree. This was the last time the PTT recorded movement for the next 10 days. Since then no new data has come through, and the PTT has subsequently switched off, which means it ceased to face upwards and charge properly. Here is a map showing the movements I've just described:



We still don't know what has happened to Gidjee. Unfortunately I won't have an opportunity to head out and investigate this any further until August, when I return from overseas. But currently there are two possible options: 1) she has been killed for some reason, perhaps as a result of being kicked out of her territory by another adult female eagle, or 2) the PTT has fallen off her back and landed in the desert, 195 km from Lorna Glen.

Keep watching Wedge-tailed Eagle Tracking to find out.

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