Birding in Ho Chi Minh

In the morning walk closeby our hotel we encountered interesting birding option of inspecting birds in vietnamese bird cages - Maybe not most pleasent way to see birds. In the park there were tens of people gathered with bird cages with various type of birds - It was left as a mystery why cages were moved all the time. First I thought every now and then someone wanted to move birds into a shade to avoid 'overheating', but it was not clear if this is really the case...