Roost- SC cockatoos: Begging and Roost at Weetangera cemetery

["boy nature" <>]

Weetangera cemetery (corner of William Hovell Dr and Drake Brockman Dr) Belconnen is a winter roost site for SC cockatoos. This afternoon 320 birds flew in (7/5/12). There was 1 dy cockatoo, begging for the whole time, but being fed every so often (perhaps only 4 times) and im sure it is dy not courtship.
Also, interesting, were a pair of wood ducks with 7 dy (about half adult size and sticking close to parents). Also another 12 adult wood ducks on the dam. Only 8 species. 4 starlings entered 2 hollows (roosting??).
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The breakdown of how the Roosting birds flew in, is as follows:
4:30 (to 4:40): 9
4:40: 5
4:50: 7
5:00: 5
5:10: 216
[Sunset was about 5:16 from my phone]. Dusk
5:20: 78
5:30: 0
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Weather was light cloud with a few spots of rain. A gap in the clouds in the west allowed the suns rays in for most of the time.
The roosting site at Weetangera cemetery is in a patch of red stringybarks, surrounded by sparse yellow box-red gum grassy woodland (understory mainly introduced grasses), virtually no mid story. The YB-RG paddocks trees are very old (some >1.5m trunks at bbh). There is a large dam. The site slopes to the WSW with views of Brindabellas. A drainage line/creek passes by the west side of the woodland (N to S). Birds tend to fly in from directly north (Higgins) down the drainage line, from NE (Scullin/Hawker ovals), from East (Hawkers South edge/ Pinnacle) (~1/3rd each).

Why have they picked this site for at least the past 4 years??
I suspect because it is a medium patch of forest, surrounded by open paddocks but with a few very large/old gums, and good views to the West (ie for predators). Plus a dam. Why here and not elsewhere though?
Benj Whitworth