Eight monitoring schemes have contributed data to this report. Six provide data on changes in abundance: these are the BTO/JNCC/RSPB Breeding Bird Survey, Common Birds Census, BTO/JNCC/RSPB Waterways Breeding Bird Survey, Waterways Bird Survey, Heronries Census and the Constant Effort Sites ringing scheme.
Two schemes, the Nest Record Scheme and Constant Effort Sites, provide data on changes in breeding productivity. Data on survival rates come from detailed analyses of the retrappings and recoveries of ringed birds, from Retrapping Adults for Survival, Constant Effort Sites and the general Ringing Scheme. In addition, information on waterbirds from the BTO/RSPB/JNCC Wetland Bird Survey is included where relevant.
The methodologies of the monitoring schemes are described in turn, including information on fieldwork, data preparation, sampling considerations and the statistical methods used in analysis. Most of the analyses were undertaken using R software (R Core Team 2018), while the preparation of tables and graphs were undertaken using SAS software (SAS 2011).
The two final parts of the methods section concern the alert system. These deal, first in descriptive terms and second in statistical detail, with the system by which the results of monitoring surveys raise alerts and thereby are brought to the attention of conservation bodies.
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