Few months back there were 7 or 8 of these ParaTweets in a tree just outside my window. Used to come and go quite often but they would always fly off together come evening and seemed to go down to the same spot somewhere near Perry Vale (i'm top of a block of maisonettes). Wondered if someone was keeping them.

Interesting BBC article here: http://news.bbc.co.uk/1/hi/magazine/6478911.stm