Bird ringing and nest recording in Britain and Ireland in 2020

ABSTRACT This is the 84th annual report of the British Trust for Ornithology’s Ringing Scheme, incorporating the report of the Nest Record Scheme and covering work carried out and data processed in 2020. An analysis of Curlew Numenius arquata ringing records was carried out to investigate recent declines. Results showed that survival rates are high, so current population declines are more likely to have been driven by low productivity. To reverse the recent population declines, breeding success would need to increase and effective conservation strategies will be needed to maintain the high levels of survival. We examined the potential opportunities and challenges of using winter ringing records to produce survival estimates, as well as other outputs such as age ratios and recruitment, by analysing 2 641 352 encounter records from the winters of 2007/08 to 2017/18: winter-to-winter survival analyses on adult birds were undertaken, initially on 44 species. Results indicated that fortnightly ringing sessions should yield sufficient data to produce useful survival estimates. This research identified a number of potential analytical and methodological options for future development. Covid-19 restrictions limited the amount of fieldwork carried out in 2020; consequently, only 72 CE sites submitted data for the year. Long-term (1984–2019) declines in abundance were observed for five migrant, one partial migrant and four resident species while long-term increases in abundance were recorded for two short-distance migrants and six resident species. Six species are exhibiting significant long-term declines in productivity while only Chaffinch Fringilla coelebs shows a significant long-term increase. Long-term trends in survival indicate increases for 10 species and declines for nine. Short-term trends, which compare the current year to the five-year mean (2015–19), show that the abundance of 10 species increased significantly in 2020, with three species being recorded in higher numbers than in any previous year since CES monitoring began. Significant decreases in abundance were recorded for only two species. Productivity decreased significantly for one migrant and five resident species in 2020; no species recorded a significant increase. Productivity was lower in 2020 than in any previous CES year for Blue Tit Cyanistes caeruleus and Great Tit Parus major. Significant changes in survival rate were observed in two species in 2020 compared to the five-year mean, with Bullfinch Pyrrhula pyrrhula increasing and Blackbird Turdus merula decreasing. A new habitat was added to the suite of standard CES habitats in 2020 in the first year of a Garden CES trial. Submissions were received from 92 sites. A new winter ringing project was also launched in 2020, following a similar methodology to CES. Submissions were received from 111 sites. The number of Retrapping Adults for Survival projects that were able to run and submit data in 2020 was 146, from 200 that were registered. In total, 60 species were monitored, with Pied Flycatcher Ficedula hypoleuca (20 projects), Starling Sturnus vulgaris (19), House Sparrow Passer domesticus (18), Sand Martin Riparia riparia (10) and Reed Warbler Acrocephalus scirpaceus (eight) the species most studied. A total of 930 091 birds were ringed during the year, comprising 98 500 nestlings, 523 777 first-year birds, 278 157 adults (birds in their second calendar year or older) and 29 657 birds whose age could not be determined. In addition, there were 212 414 recaptures of ringed birds at or near the ringing site. In total, 42 987 recoveries (birds found dead, recaptured or resighted at least 5 km from the place of ringing) of BTO-ringed birds were reported in 2020. The Appendix highlights a selection of recoveries that have extended our knowledge of movements, as well as longevity records established during the year. A total of 23 928 NRS submissions were received in 2020, far fewer than usual due to Covid-19 restrictions being in place during the height of the nesting season. As the seasonality of nest records was biased towards the end of the breeding season, after Covid-19 restrictions had lifted, it was not possible to generate meaningful NRS trends for 2020. Permits or licences to disturb breeding birds on Schedule 1 of the Wildlife and Countryside Act 1981 (as amended) were prepared and issued to 611 ringers and nest recorders in 2020. During 2020, the use of special methods was authorised for 1182 marking projects and 146 trapping projects.