I first observed the unusual behavior of long-tailed parakeets feeding on the old roof tiles in my neighborhood last year after a heavy downpour.
On the evening of 8 January 2015, I again observed the same behavior with a a flock of long-tailed parakeets that made a stop over in the evening before they head to their roosting site. They were up in the rain trees as usual but a couple of birds started to descend onto a neighbor's roof then more started to follow. Soon there were over fifty birds on the roof peeling off material from the roof tiles to eat.
I managed to capture this behavior as it was relatively quiet and the birds didn't mind the couple of people walking around below them. They fed for almost 10 minutes before a neighbor's car horn scared the flock into flight.
After some speculation, it was assumed that like macaws and parakeets of South America, our long-tailed parakeets were harvesting clay. Upon checking with SK Khew, I found out that old roof tiles in the late 50s were made of concrete.