The point of a constant effort site (CES) is that the same nets are set in the same places, for the same length of time, over 12 sessions approximately 10 days apart, year on year. This is the ninth year of my CES at Lower Moor Farm, with 2020 being missed out due to Covid restrictions. So I now have data for eight full years. What it shows, in the lead up to this year’s CES, is a significant decline in the catches over the period. I am currently doing an analysis of the possible reasons for this for my annual report to the Wiltshire Wildlife Trust.
When looking at each full year in turn, (1st April to 31st March) even with a significant spike in numbers in 2019, the overall trend is a decline in average catch size for the site:
The number of species is not as much of an issue (yet?):
There is a slight declining trend. but nothing as clear as the reduction in the size of the catch. When I shut this down to just the CES period, the decline becomes rather clearer:
The trendline shows that there has been a significant reduction in the size of the catch but, unlike for the year as a whole, there is also a clear reduction in the number of species since 2019. So to 2023!
The first session delivered 21 birds: 9 ringed and 12 retrapped from 10 species. Although still another reduction, this compared favourably with session one last year: 24 birds: 11 ringed and 13 retrapped from 8 species. On to session two. Last year delivered 20 birds ringed and 8 birds retrapped from 12 species. So what happened in CES 2, 2023:
Unfortunately I was working solo for this session, so I had a 4:30 start to get the nets up and open by 5:30. There was no rush: despite having them open on time I didn’t catch my first bird until 7:00. It was slow all morning: and the end catch was disappointing, to say the least. I was joined by Laura and son Adam at just after 8:00, and then dad Mark at 10:00, having dropped his other son off for a Duke of Edinburgh Award route march first.
Adam, in his fledgling career as a ringer, got to ring a couple of birds: a Blackcap and a Robin. The highlight of the morning (there was one) was a newly fledged brood of Robins. I extracted three of them close together in the same net. On examination, all still had both wing and tail feathers still growing. The wing feathers were between 5 and 10mm shorter than I would expect but the tail feathers were less than half full grown. It seemed to me likely that they had fled the nest in response to some sort of threat. We processed them and then returned them to the area that we had originally found them in, in case the parents were in close proximity. They all flew off okay. Interestingly, in my last round I recovered one of the youngsters, but in the net ride furthest away from where we originally caught them.
The list for the session was: Great Tit (1); Long-tailed Tit 1; Wren (1); Dunnock (1); Robin 3(1); Blackbird (1); Blackcap 2; Garden Warbler 1(1); Chiffchaff (2); Goldcrest 1. Totals: 8 birds ringed from 5 species and 8 birds retrapped from 7 species, making 16 birds processed from 10 species. So, this session was over 40% down on last year! I hope that things pick up in future sessions or I might have to consider whether the effort required is matched by the return.
As ever, Laura, Mark and Adam helped me pack away at 11:30: I was extremely grateful, and away from site by 12:30.
Ringing In The Braydon Forest & Beyond 