Bird ringing and nest recording in Britain and Ireland in 2017

Abstract

ABSTRACTThis is the 81st 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 collected and processed in 2017. Demographic data contributed to several research studies during the year, including a review of the conservation status of Raven Corvus corax and the impacts of licensed control. This quantified the extent to which non-breeding birds could be removed without impacting overall population sustainability, as well as the data permitted, but noted that a better understanding of age-specific survival rates was required. Nest Record Scheme data contributed to a large-scale collaborative study investigating the impact that temperature and rainfall have on the timing of events throughout the annual cycles of 10 000 animal and plant species across different trophic levels. The results indicated that the speed of response was greatest at low trophic levels. Future changes under a range of emission scenarios were estimated; these results indicated that advances in timing would be greatest for primary consumers. A statistical method was developed, using nest record data, to quantify nest failure, taking into account uncertainties generated during data collection. The method was applied to Blackbird Turdus merula records to compare survival rates of nests in gardens with those in the wider countryside. Survival in suburban areas was found to be higher than in urban or rural areas, and nests survived better in wetter conditions across all habitats. In order to quantify any welfare impacts of capturing wild birds, we examined the frequency with which passerines were reported to have died either whilst in the net or during handling. Analyses of capture data submitted from 2005 to 2013 indicated that the average mortality rate is around 0.1%, and that this is consistent between years. Most fatalities occurred before individuals had been extracted from the nets and juveniles appeared to be at greater risk than adults. In 2017, 135 CE sites submitted data. Long-term (1984–2016) declines in abundance were observed in four migrant, one partial migrant and one resident species and concurrent increases in abundance continued to be recorded in two short-distance migrants and four resident species. There was no change to the 10 species which exhibited significant long-term declines in productivity; only one species, Chaffinch Fringilla coelebs, exhibited a significant long-term increase in productivity. Compared to the five-year mean (2012–16), the abundance of six species increased significantly in 2017; Treecreepers Certhia familiaris were seen in greater numbers in 2017 than in any other year since CES monitoring began. Conversely, the abundance of six species fell significantly in 2017, with Chaffinch and Greenfinch Chloris chloris numbers at their lowest since CES monitoring began. Productivity increased significantly for three species in 2017 and decreased for eight species. The only significant change in survival rates between 2017 and the five-year mean was for Wren Troglodytes troglodytes, although the survival rate for Song Thrush Turdus philomelos was at its highest. The number of Retrapping Adults for Survival submissions fell slightly in 2017 to 195; 11 projects ran for the first time. In total, 58 species were monitored, with Pied Flycatcher Ficedula hypoleuca (20 projects), House Sparrow Passer domesticus (16), Starling Sturnus vulgaris (15) and Sand Martin Riparia riparia (11) continuing to be the most-studied species. Once again, over a million birds (1 020 356) were ringed during the year, comprising 165 565 nestlings, 500 580 first-year birds, 321 945 adults (birds in their second calendar year or older) and 32 266 birds where the age could not be determined. In addition, there were 242 719 recaptures of ringed birds at or near the ringing site. In total, 41 049 recoveries (birds found dead, recaptured or resighted at least 5 km from the place of ringing) of BTO-ringed birds were reported in 2017. The Appendix highlights a selection of recoveries that have extended our knowledge of movements, as well as longevity records established during the year. NRS submissions in 2017 exceeded 4 0 000 for the eighth consecutive year, with a total of 43 570 records received. Mean laying dates for 22 species were significantly earlier than the five-year mean (2012–16) with none of the 52 species analysed laying significantly later. There was a significant increase in breeding success (fledglings per breeding attempt) for two species in 2017, compared to the five-year mean, with one decreasing significantly. Permits or licences to disturb breeding birds on Schedule 1 of the Wildlife and Countryside Act 1981 (as amended), were prepared and issued to 580 ringers and nest recorders in 2017. During 2017, the use of special methods was authorised for 584 marking projects and 67 trapping projects, a 4% decrease from 2016.