NOTE: Species accounts are no longer included within the BirdTrends report and all links to individual species in this BirdTrends report now point to the relevant species page in BirdFacts. Species trends can now be viewed in the "Trends Explorer" which allows you to view a range of temporal trends for each species.
The BirdTrends report raises species alerts for population change to conservation bodies when the best available estimates of long-term decline are statistically significant and pass criteria set at -25% and -50%.
Species with declines close to these threshold values often change category between years. Discussion tables A1–A3 indicate five changes to the alerts since BirdTrends 2020, affecting five different species.
- For the amber-listed Common Sandpiper, the 45-year WBS/WBBS decline now raises a high alert. The 25-year trend continues to raise a lower level alert.
- The green-listed Swallow now raises a lower level alert for both the 25-year and the 53-year CBC/BBS trend, following a steep decline over the last ten years.
- The green-listed Chaffinch has also experienced a steep short-term decline and now raises a lower level CBC/BBS alert over the 25-year period.
- The 45-year WBS/WBBS trend for Little Grebe and the 25-year CBC/BBS trend for Garden Warbler again raise formal alerts (high alert and lower level alert respectively). Thes species have raised formal alerts in some of the recent BirdTrends reports for the longer-term and/or 25-year periods but not in others, as the confidence intervals have changed and hence the estimates have not always been statistically significant.
Amber and red listings use similar criteria and were reviewed in 2021. This report, using one further year's data not available to BoCC5, suggest potential updates to current conservation concern for Common Sandpiper, Swallow and Chaffinch and possibly for Garden Warbler. Although Little Grebe raises an alert on linear waterways, BBS data suggest that numbers are stable or possibly increasing in other habitats.
The number of species for which potential updates to current conservation concern are suggested by the alerts has increased in recent years (Table 1).
The alerts for CES (Table A5) show changes from BirdTrends 2020 for two species. The 36-year trends for Greenfinch now raises a high level alert rather than a lower level alert, as does the 25-year trend for Reed Bunting. Conversely, the 36-year trends for both Sedge Warbler and Whitethroat now both raise lower level rather than high alerts.
This report should be cited as: Massimino, D., Woodward, I.D., Hammond, M.J., Barber, L., Barimore, C., Harris, S.J., Leech, D.I., Noble, D.G., Walker, R.H., Baillie, S.R. & Robinson, R.A. (2020) BirdTrends 2020: trends in numbers, breeding success and survival for UK breeding birds. BTO Research Report 732. BTO, Thetford. www.bto.org/birdtrends