Contents of report
Breeding Bird Survey
Common Birds Census
Constant Effort Sites
Nest Record Scheme
Waterways Bird Survey
Alerts
Summary
What the categories mean
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What the categories mean
       
6. SPECIES ACCOUNTS
       
   Depending on the availability of data (all species are not covered by each scheme), each account usually consists of the following:
       
  1) Conservation Listings: the conservation status of the species is graded with reference to the JNCC/Country Agency Conservation Importance List (JNCC 1996) as follows:
       
    Table 1: IUCN globally threatened species. These species require monitoring of populations and the preparation of International Species Action Plans to ensure effective conservation.
    Table 2: Uncommon and, rapidly or historically, declining British breeding birds. These species require monitoring of populations and the preparation of Species Action Plans to ensure their effective conservation.
    Table 3: Rapidly declining, but common British breeding birds. For these species the JNCC and Country Agencies will, in collaboration with Non-Governmental Organisations, investigate causes of decline and consider their conservation requirements and, where appropriate, prepare Species Action Plans to ensure effective conservation.
    Table 4: Species listed as moderately declining, historically declining but common, internationally important, localised or 'threatened in Europe' British breeding birds. These species require monitoring of populations and, where appropriate, the preparation of Species Action Plans to ensure effective conservation.
    Unlisted: Other British breeding birds.
       
    Species are also categorised with reference to the Birds of Conservation Concern listing (Gibbons et al. 1996) as follows:
       
    Red: generally equivalent to Tables 1, 2 & 3 of the JNCC list.
    Amber: generally equivalent to Table 4.
    Green:

generally equivalent to unlisted.

       
    The main reason for listing as Red or Amber is provided in parentheses as follows:
     
   
  • >50% Population decline (generally from CBC data)
  • >50% Distribution decline (generally from the New Breeding Atlas, Gibbons et al. 1993)
  • 25-49% Population decline (generally from the New Breeding Atlas, Gibbons et al. 1993)
  • 25-49% Distribution decline (generally from the New Breeding Atlas, Gibbons et al. 1993)
  • Historical decline (in UK between 1800-1995, assessed by literature review)
  • Important breeding and/or wintering population (>20% of European population in UK or >50% of UK population in just 1-10 sites)
  • European Status (species with unfavourable conservation status in Europe
       
    The UK Biodiversity Steering Group produced three lists of species of conservation concern (Anon. 1995) that have since been rationalised to two lists (Anon. 1998). These are indicated as follows:
     
    Biodiversity Steering Group Priority Species List:
species which are globally threatened or rapidly declining in the UK (i.e. by at least 50% in the last 25 years); and for which costed Action Plans have been prepared (previously the "short" and "middle" lists)
       
    Biodiversity Steering Group Conservation Concern List:
this includes species on the Priority List but also species for which UK has >25% of the world or appropriate biogeographical population; species for which numbers or range have declined between 25 and 49% over the last 25 years; species which are found in <15 10-km squares in the UK; and species listed in international or national conservation legislation.
       
  2) Long term trend: This summarises the trend in population size over the past 30 years from CBC or shorter for WBS and CES. The terms mean the following:
       
   
  • Rapid decline: >50% (and statistically significant) population decline from CBC, WBS or CES.
  • Moderate decline: 25-49% (and statistically significant) population decline from CBC, WBS or CES.
  • Shallow decline: <25% (but statistically significant) population decline from CBC, WBS or CES.
  • Decline: derived from other data sources or when statistical significance is unknown.
  • Probable decline: as "decline" but the information is not as certain - see the status summary for reasons.
  • Possible decline: as "decline" but the information is less certain than "probable decline" but it is still most likely that there has been a decline - see the status summary for reasons.
  • Stable/Fluctuating, with no long-term trend: where the confidence limits of the decline encompass 0 (or no overall change).
  • Uncertain: where the information from two monitoring schemes provide conflicting trends or if the schemes are unrepresentative of the species' UK population.
  • Unknown: no information on the UK population trend is available.
  • Increase/Probable Increase/Possible Increase: data from other sources, see "decline" above.
  • Shallow increase: 10-49% population increase, where the lower confidence limit is >0 (but see Alerts Section 2.7), measured by CBC, WBS or CES.
  • Moderate increase: 50-99% population increase, where the lower confidence limit is >0 (but see Alerts Section 2.7), measured by CBC, WBS or CES.
  • Rapid increase: >100% population increase, where the lower confidence limit is >0 (but see Alerts Section 2.7), measured by CBC, WBS or CES.
     
  3) Status summary: this provides a brief summary of the trends detailed for the species and indicates why such changes might have occurred with reference to published information when available.
       
  4) Population trends graphs: the first of these shows the changes in abundance for that species over the period from 1966-1999, as measured by the Common Birds Census. For some species, the Waterways Bird Survey, Constant Effort Sites scheme or Breeding Bird Survey provides the most representative trend and is shown. After the following table, graphs are presented to show trends in other habitats and regions from the other monitoring schemes. Details about how the graphs are calculated are provided in the Methods (Section 2) for each scheme. For CBC and WBS, the graphs show a smoothed line (blue) and its 85% confidence limits (green); for CES, Heronries Census and BBS, annual estimates are shown (blue) together with their 85% or 95% (BBS) confidence limits (green), and for the first two schemes a smoothed line (red).
       
  5) Population trends table: this provides details of percentage changes in population size over the past 30 years (or a shorter period, depending on the availability of data), 25 years, 10 years and 5 years. It lists the period of years concerned, the average (mean) number of census plots which contained the species in each year and the upper and lower confidence intervals ("limits") for a population decline. The Alert column indicates whether a statistically significant population decline over the period is greater than (or equal to) 50% (>50) or between 25 and 49% (>25) (see Alerts, Section 2.7 for further details). The comment column lists any caveats that must be considered when interpreting the changes. The caveats are:
       
   
  • Small sample: for CBC, WBS and CES data, a mean sample size of less than 20 census plots was available; for BBS data, a mean sample of <50 plots was available
   
  • Unrepresentative?: the CBC data may not be representative of the population as a whole either because the average abundance of a species in 10-km squares containing CBC plots was less than that in other 10-km squares of the species' distribution in the UK (as measured from New Breeding Atlas data (Gibbons et al. 1993)), or where average abundances could not be calculated, expert opinion judged that CBC data may not be representative
       
  6) Productivity trends table: this provides details of changes in productivity over the past 30 years (or a shorter period, depending on the availability of data). It lists the period of years concerned, the mean annual sample, the type of trend, if the trend is significant then the predicted values (from the smoothed trend) for the first and last years and their difference is listed, and the existence of any caveats that must be considered when interpreting the data. The caveat "small sample" is given when the mean number of records per year is between 10-30 for the Nest Record Scheme, or when the mean number of CES plots was <20 per year.
       
  7) Productivity graphs: graphs of changes recorded by the Constant Effort Sites Scheme or Nest Record Scheme illustrate significant trends in population size or productivity. For NRS data, annual means (averages) are provided with error bars to denote 1 standard error either side of the mean (in green); regression lines (in black) and the upper and lower 95% confidence intervals of these lines (in blue) are also shown. For CES data, the annual values are plotted (blue) with their 85% confidence intervals (green) and a smoothed line (red) is put through these points (see Section 2.5 for details).
       
   




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