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I don't find this particularly convincing, to be honest. I wonder how reliable it is to be making the ID based on the gular patch alone (and it is less than 90 degrees here, anyway). It was said previously that very white-necked birds were sinensis, but that has since been disproved. Not convinced...
I quite like this ID guide though!
My Flickr photos...
Lat/Lng: 51.5, -0.4
OS grid ref: TQ1584