Hi Jeff Myself, Tony Darby and Jamie Dunning have been counting and monitoring the south Manchester population for a number of years including Tony and I finding the roost site of 2013 and its subsequent relocation last year. Most of these counts have been made by photographing and then counting the birds leaving the pre-roost in Platt Fields Park a few hundred yards from my house. As they also fly over my house in the morning when I'm in bed I make a note of the time of passage every day I hear them. I nearly have enough data to plot the average time after dawn that they disperse from the roost. Me, Tony and Steve Atkins also assisted the BBC with a (rather misleading) news story on the Manchester population.
Not sure if you are aware of it but there is an earlier thread on this subject, on this forum, from November 2014 where a few views were aired on the subject of the growing Ring-necked Parakeet population.
Having found an interesting article on monitoring alien species in Belgium http://www.birdguides.com/webzine/article.asp?a=5265 I have been attempting to compose a contribution to the debate using Ring-necked Parakeets in Manchester as an example. These birds have been regularly present since at least the early 1980s but have it is only recently that they have really established an expanding population. Studying this thread I came up with the following largest counts (mainly autumn pre-roost counts) by year. I know that Ian McKerchar will have more reliable figures but this is the best that I could do a short notice.
This looks like this could be the beginning of an exponential increase as occurred in London many years ago. I see that there are no large counts yet recorded for this autumn but for fun I would guess that a figure of 120 is possible! I have no idea how many pairs may be breeding but this population may be on the cusp of being fully sustainable even if attempts were made to remove them (even including egg-collectors). I may be way off track here and I would welcome any (hopefully constructive) comments on this.
