Saturday marked the end of the fourth year of the constant effort site at Lower Moor Farm. The point of the CES scheme is, by putting the nets in the same place, for the same length of time, year on year, standardising the variables, you can trace trends in the bird population at the site, being relatively confident that changes in the population are just that and not down to moving the nets to better positions.
Saturday’s session was quieter than the same session last year, which was a bit unfortunate given that we had a large team out. Jonny, Ellie, Steph and I were joined by Tim, one of the Wildlife Trust’s Estate Management Team, coming along for a taster session.
The list for the day was as follows: Treecreeper 1; Blue Tit 1; Wren 1(1); Dunnock (3); Robin (5); Blackbird 2; Reed Warbler 2; Blackcap 11(1); Chiffchaff 5(1); Willow Warbler 1; Goldcrest 1; Bullfinch (1). Totals: 25 birds ringed from 9 species, 12 birds recaptured from 6 species, making 37 birds processed from 12 species.
Over the last four years we have seen a steady reduction in the number of birds caught:
The change is mainly due to a significant fall in the number of birds ringed between 2015 and 2016, remaining relatively stable in 2017 but falling away a lot more in 2018. In 2018, the number of retrapped birds has fallen compared to the previous three years. The number of species ringed and recaptured have remained relatively constant:
The nets are set in the following positions:
When I looked further at the data, it is clear that the main issue revolves around one set of nets:
Ride 2 has shown a steady reduction in numbers caught over the period. This ride has been subjected to several management procedures over the last couple of years: thinning of the trees to the side of the path away from the brook, development of scallops, top encourage butterflies on the brook side, and removal of significant amounts of bramble from that area as a result. It will be interesting to see whether, as these procedures mature, the catch returns to its previous level. The numbers were falling before these changes were made, however, and the same changes have been made to ride 3, which has not shown such a dramatic, nor continual, reduction.