Any ringing session where you ring 80 new birds of which 64 are migrants is good in anyone's terms. This morning we ringed 64 migrants including 20 Chiffchaffs, 17 Reed Warblers, 11 Blackcaps, 8 Willow Warblers and 7 Sedge Warblers--as well as other species such as Kingfisher. But a close inspection of our results so far shows up some remarkable figures which seem to confirm our fears about the potentially poor breeding season this year.
We suspected it might be the case because of the cold late Spring weather as well as the local issue of slow growth of the nesting and feeding vegetation round the reservoir--in particular the Phragmites reeds, the Glyceria grass and the brambles.
This small table shows a comparison of the 2020 and 2021 seasons up to 4th August--looking at the four signature species breeding at Belvide:-
2020 2021
Reed Warbler 171 109 -36%
Sedge Warbler 139 62 -55%
Chiffchaff 151 101 -33%
Blackcap 123 78 -36%
These are pretty stark figures and do seem to provide evidence to support our theory. Further comparisons as time moves on are less valuable because any late breeding will be masked by any influx of birds during migration.
It will be interesting to see what the picture is like across the country as results come through--but it's likely to be some time before such results are analysed. Let's hope this is just a 2021 glitch rather than being the start of a longer term decline in breeding success.
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