Yellow-tailed Black Cockatoos usually disappear for the summer. I suspect they head for the cooler, higher parts of the Mt Lofty Ranges. This summer we've had a family of three around most of the summer.
What is perhaps more interesting is that already we're seeing an increase in numbers which doesn't usually happen until about late March. Last week we saw a flock of thirteen & this week a flock of at least twenty two. The weather has been reasonably mild during the last week or so although the heat is now building again.
I know the big cockatoos migrate to all their food sources and the Yellow-tailed ones travel through Tenterfield and head south. They come from the north, north-east direction. They could end up in S.A. for all I know. I've only seen less than 10 yellow-tailed Black Cockatoos this summer/autumn fly through town. I guess their numbers are probably decreasing in this area as they fly through. Having been so hot since last October I can only guess at the possibility of their food sources being ready earlier because of the heat and accompanying rainfall. Its the only thing that makes sense to me.
I'm at Tenterfield, NSW. (Formerly known as "Hyperbirds".)
Some relatively large groups of these were present around my area all summer, Woko. They would pretty reliably be flying over my backyard each evening, looking to be heading between the Hallet Cove CP and Sturt Gorge/Happy Valley type areas. Haven't seen them now for a few weeks, but they were like clockwork through summer. Have seen them quite often in SG at various times of the year.
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Mike
https://flic.kr/ps/aF4bq
In the last week or so it's been common to see flocks of well over 20. 32 yesterday is the highest number I've counted this autumn. I wonder if their numbers are recovering on the Fleurieu Peninsula, detritus. This would be great news if it is so. From what I understand this is rather a contrast with WA where the government there seems intent on making cousin Carnaby's Cockatoo extinct.