One of the great, albeit ‘exotic’, wildlife spectacles in Bexley in recent years has been the sight and sound of Ring-necked Parakeets (Psittacula krameri) flying in successive groups out of various sites in Bexley towards their final night time roost sites, over a short period of time before dusk, especially in winter.
I have made significant counts at Bexley Park Woods, Bursted Woods, Martens Grove, Lamorbey Park (where one can get the closest views) and Loring Hall (Footscray Meadows). Birds have headed in a west/south-west direction, suggesting that the final destination is the Hither Green Cemetery roost where 5,800 birds were counted on the 10th of October 2010 (Ralph Todd, July-Oct 2010 Bexley Bird Report). Other south/south-east London roosts have been Sutcliffe Park and Brockwell Park.
The parakeets are known to gather in staging posts before the last leg of their journey, and the counts from the sites mentioned above have almost certainly included birds from further afield, such as those at Crayford Marshes and Franks Park. Danson Park has been a major aggregation point in Bexley for birds leaving together for the communal roosts further into south-east London, and has produced by far the highest counts of all the Bexley sites mentioned.
The question in my mind has been, at what point do numbers become large enough at aggregation points for new roosts to be formed? I was at Danson this afternoon (23rd December), and positioned myself at the west end of the park ready to do my first count for a long time. But there wasn’t the usual amount of noise, and a measly total of just 13 birds flew out over the school field, heading south, at 16.13. Where were the rest, given previous counts in the hundreds?
The answer turned out to be in two tall adjacent Poplars on the north side of the lake, and two 30-35′ trees between them. My estimated count of the birds in silhouette and amongst fairly dense branches (it now being quite dark), was about 940. It was clear they were staying put for the night.
So is this is a new phenomenon, or something I’d missed in the past, and how do the numbers relate to what has happened before?
My previous Danson ‘departure-to-roost’ counts were as follows:
22/10/2012 – 91
3/1/2013 – 255
18/3/2013 – 301
18/11/2013 – 292
24/12/2013 – 339 (may have missed some)
6/1/2014 – 479
3/2/2014 – 442
21/2/2014 – 228
Since there were large departures both before and after Christmas, it is unlikely that once in a while the birds decided to spend the night at Danson during these periods. Something has triggered them to do so now. In fact I had noticed last winter that a handful of birds were staying put in Poplars, albeit still being fairly active rather than roosting, quite some time after the great majority of birds had left and when it was quite dark. Perhaps that was the beginning of the change? The internet at least does not suggest any felling of roost trees at Hither Green, and my own recent visit to Sutcliffe Park indicated no such changes there.
What of the numbers? It may be noted that the figure of 940 is higher than the highest previous departure counts I have for Danson, and higher than the Danson figure plus those for birds from further east in Bursted (most recent count 144) and Martens Grove, even if they hadn’t previously aggregated at Danson themselves, so birds from multiple sites are likely to be involved.
One web briefing says that birds are reluctant to fly beyond commuting range of a roost (15km/approximately 9 miles – though it is unclear whether this means both ways, or the one way distance), so this new roost site may be something associated with an eastwards range expansion.
It will be interesting to see whether this behaviour persists, whether the roost size grows, and at what rate. Tall trees are known to be favoured for roosting, and those used at Hither Green are also Poplars. There were some tall Poplars very close by at Danson that were not being used this evening, and if they were to be, 2,000 birds could probably be accommodated with ease.
The next thing to do is to get an accurate count of the birds flying into this new roost, and to get some idea of the compass points they appear to be coming from. Any volunteers?
(Chris Rose)
