This report uses a system of alerts agreed between the providers and users of population monitoring information in the UK. The system provides alerts to population declines of 25-49% and of >50% over short, medium and longer terms (5 years, 10 years and 25+ years respectively). These help to highlight the scale and timing of declines as an aid to interpreting the trend graphs presented. Our main emphasis is on long-term declines measured on the length of the longest time series available (usually 35 years) and over 25 years as this is the period that is normally used to determine red and amber listing (Gregory et al. 2002). Alerts triggered over the short term for individual species should be considered as early warnings, indicating that conservation issues may be developing for these species. However, it is possible that such declines may be due to chance fluctuations in abundance from which the population is able to recover without assistance. The rapid, short-term decline of a suite of similar species should be considered as a stronger indication that potential problems may be developing. Details of the alerts and methodology used in this report are given in the methods section.

Except where otherwise indicated our discussion is based on the best long-term trend that is available for each species. These are the trends presented as the main trend graph for each species. Details of estimating and comparing trends are given in the methods section. Full details of all trends available for each species are given on the species pages. Summary tables of all alerts raised by each scheme are presented in the appendices.

It should be noted that a number of species included in the PSOB lists are not covered by this report. Thus tables relating to PSOB list status do not include all species that are on the relevant PSOB list.