Here we present the latest analysed trends in abundance, productivity, demographic parameters and diet of breeding seabirds, from the Seabird Monitoring Programme (SMP), along with interpretive text on the likely causes of change based on recent research. It replaces and builds upon the now discontinued annual publication Seabird numbers and breeding success in Britain and Ireland. Like it, this online report will be updated annually. Trend information is presented at the UK level and separately for Scotland, Wales, England, Northern Ireland, Republic of Ireland, all-Ireland, Channel Islands and Isle of Man. Interpretation of trends and reasons for change are given largely at the UK level, unless there is country-specific evidence. A download of data points presented in the graphs of abundance and productivity under species accounts is available on request. The table below contains links to the species accounts and provides at-a-glance UK population trends (as percentage of change in breeding numbers) from complete censuses undertaken in 1969-70 (Operation Seafarer), 1985-88 (Seabird Colony Register, hereafter SCR), and 1998-2002 (Seabird 2000). Change from 1998-2000 to 2018 (i.e. over the period since the last national census) is estimated from trends derived from the SMP sample of colonies; this analysis is only available for species with sufficient data to accurately estimate trends. Any marked differences in the trend calculations between the last census and 2018 is due to a recent increase in sample data as part of the current seabird census Seabirds Count (2015-2020).