Before setting up the CTBSG, it has been necessary to get the correct permission to access Cabot Tower early enough in the day to make it worth while, as most movements of the types of birds we will be monitoring take place before the tower is open to the public.
After gaining access, a few trial sessions have taken place, with mixed results.
On Friday the 23rd of September things were looking promising with lots of movements of gulls down the Avon into Bristol, a couple of peregrines, a few cormorant, a large conspiracy of 21 ravens grouped tightly together just overhead, and movements south of 62 meadow pipits, 20 grey wagtails and 5 pied wagtails. The session lasted c2 hrs from 6:45 , winds were light with few gusts (SW 10 – 18mph), it was bright and clear with temperatures of 14°C.
For the second preliminary session on Sunday the 25th, I was joined by Ed Drewitt. After being greeted with a grey heron and a peregrine we registered no movement of any passerines apart from perhaps a couple of grey wags that we heard passing over. We were up there for c1.5 hrs, again from 6:45, winds were more gusty (S 12 – 21 mph), grey with drizzle and temps of 15/16°C.
These results perfectly illustrate the nature of bird migration and its unpredictability. Within the space of 2 days, significantly different results with conditions not too dissimilar. The most likely explanation for the lack of movement on the Sunday, was that the weather had turned after a particularly mild day on Saturday with light winds and plenty of sun. Hirundines were definitely making the most of the Saturday’s conditions, with c1k moving south down the Avon Gorge.