Subject: Raptors overflying Po Toi above 2000 ft [Print This Page] Author: wgeoff Time: 18/10/2007 16:58 Subject: Raptors overflying Po Toi above 2000 ft
At 7am this morning, I was watching visible migration from the lighthouse on Po Toi. I was following a Yellow Wagtail flying overhead using my binoculars when I noticed another bird much higher above. I followed this bird and found it was one of a pair, both birds drifting slowly south west in a circling movement. From the shape and size, I think they were Amur Falcons. They were invisible to the naked eye (mine at least) and must have been flying above 2000 feet.
After this, I started to search the sky with binoculars for more sightings, a pretty hopeless task, but ten minutes later I saw another group of five birds at around the same height. These were flying more directly in a loose flock, and from the shape and flight I think they were sparrowhawks, possibly Chinese Goshawks.
I didn't see any more in the next 30 minutes.
This observation would indicate that, under favourable weather conditions, certain raptors and perhaps other autumn migrants are overflying Hong Kong at heights which would make them virtually invisible from the ground. The wind early this morning at lighthouse level was E/NE force 5 and the lower clouds were moving west/south west, an ideal direction for migration. Author: kmatthew Time: 19/10/2007 02:27
Very interesting observation Geoff! Does that mean that certain species of raptors that are not recorded every year or are rare in some years might be cause by of the weather?? Author: wgeoff Time: 19/10/2007 06:34
Hi Matthew
I'm not sure. The winds in Hong Kong in October are very consistent from the NE quadrant every year so I don't think this will be a factor, although the strength may vary - this year the winds seem stronger than last.
If some species of raptor regularly migrate at height through Hong Kong in autumn, I'm not sure what conditions will bring some of the birds, at least, down to ground level. Rain is not frequent in October. It may be just a chance factor - after each migration leg, they must come down somewhere and they may stay around a short while before flying on. Author: kmike Time: 23/10/2007 10:30
Raptors are diurnal migrants - night time will bring them down.
I suspect the need/desire to feed will also bring raptors into places where they can re-stock for the ongoing journey - hence the good numbers of Amur Falcons over the wildfowl collection at Mai Po las autumn.
It has been thought for a few years that Amur Falcons go through high and it seems likely that in good conditions many other raprtors do too - not many people have the patience to stare into an empty sky!
I agree wth goeff that there is little in the way of adverse weather in october, so its unlikely that birds will be grounded by rain or cloud.
Cheers
Mike K Author: wgeoff Time: 25/10/2007 21:18
Thanks Mike.
I've given up staring at the sky now - nearly broke my neck.
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Does that mean that certain species of raptors that are not recorded every year or are rare in some years might be cause by of the weather??