(This entry was written on 23rd May)
This week was all about weather and its effect on migrating birds.
The migrating birds in question were mostly small bitterns and herons. Mid May is the main spring migration time for them when I believe they are making long crossings of the South China Sea from North Borneo and South Philippines into South China. Here is the 8am HKO Weather Chart for Monday 19th May.
Weather conditions in the southern part of the South China Sea are perfect for a long northerly migration – light southerly winds. So the birds set off on say Sunday evening. Nearing the coast of South China on Monday night, they encountered the NE winds and heavy rain of the depression. The depression stayed throughout Tuesday (there was heavy rain in Hong Kong on both Monday and Tuesday) so the birds had to fight their way through to reach the South China coast. Many would not have made it and drowned in the sea. Those that got through (‘the fittest’ – Darwin’s Theory of Evolution) will survive to produce the next generation.
On Po Toi, it was obvious on Tuesday that birds were arriving in large numbers but the weather was too bad to do much bird-watching. The rain stopped about 3am on Wednesday morning. Wednesday was dry, perfect for watching birds and with 37 species of spring migrant, it was easily the best day of this spring. The numbers of birds were terrific – of the small bitterns and herons, a Grey Heron, 33 Cattle Egret, 7 Striated Heron, a Malayan Night Heron, 44 Yellow Bitterns, 29 Schrenck’s Bittern, 2 Cinnamon Bittern and 8 Black Bittern with some of most species seen flying in off the sea from the surrounding islands and one amazing flock of 22 Schrenck’s Bittern which flew up the east coast of Po Toi at 6.40am.
Here some birds flying in (four birds from the Schrenck’s Bittern flock and a pair of Black Bittern) and some on the land (Striated Heron, Yellow, Schrenck’s, Cinnamon and Black Bittern. As you can see from the photos, bitterns could be found anywhere on the island, beaches, fields, trees and the lagoon and some did not survive even though they reached land.
Also other lands birds seen, Chinese Goshawk, Greater Sand Plover, Red Turtle Dove, Oriental Cuckoo, Brown Hawk Owl, Himalayan Swiftlet, Dollarbird, Pale Martin, Pechora Pipit, Black-winged Cuckoo-shrike, Ashy Minivet, 89 Brown Shrikes on Wednesday, Brown-headed Thrush and some other thrushes, Lanceolated and Pallas’s Grasshopper Warbler as well as the regular Arctic Warbler and Grey-streaked Flycatchers.
Here photos of the Himalayan Swiflet, Pale Martin, and Black-winged Cuckoo-shrike
Many bitterns could be seen flying off on Wednesday evening and Thursday morning after only a very brief stay and by Thursday afternoon the numbers were well down on Wednesday. Most will be gone by the weekend and with no more weather systems forecast for next week, this may well be the end of Po Toi Spring 2008. But what a way to go!
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Last edited by wgeoff at 18/08/2010 08:25 ]