Data checks

After receipt, the PECBMS coordination unit checks the national data on species numbers, indices and trends for inconsistencies; it checks for instance if the scheme all-sites totals exceed the national population size known from other sources. Suspicious data coming from countries with more than 10% of PEBCMS European bird populations (see below) are examined in detail. If any problems are encountered, the coordinators of national monitoring schemes are consulted. Additionally, documentation from previous data analysis is checked and used for decisions in some cases. Data with persistent serious data problems are excluded from computation.

Suspicious data – national species data are subject to closer examination when:

  • Slope (Multiplicative) < 0.6
  • Slope (Multiplicative) > 1.5
  • Slope (Multiplicative) standard errors > 0.5
  • Percentage of scheme time totals of the species > 95% of national population size of the species in European Red List of Birds (BirdLife International 2015)
  • Ratio of national population size to scheme time totals > maximum of species population size in European Red List of Birds (BirdLife International 2015)
  • Number of zero counts < 1
  • Number of missing counts < 1
  • Index value < 0.5
  • Index value > 1000
  • Scheme time totals < 1
  • Scheme time totals > 1000000
  • More than one year with index = 100 and SE = 0 present in the results

For these data checks an automatic system has been developed by Statistics Netherlands.

All national indices – species by species – are also checked for their interannual consistency (comparison with previous trends and indices) and all suspicious and inexplicable inconsistencies in indices are examined in detail. Also for this procedure a special tool has been developed.