Questions & Answers
Compiled by Petr Voří¹ek, Arco Van Strien, Willy Van Strien, Jana ©korpilová, Ian Burfield and Richard D. Gregory
Updated on 15 July 2015
In a form of questions and answers, this section aims to help understanding methods of data collation and analysis within the Pan-European Common Bird Monitoring Scheme. The section is complementary to the section Methods. We expect the Questions and Answers will be updated on regular basis and appreciate suggestions for improvements or completely new questions on methods of production and interpretation of supranational species population trends and indicators. Please send comments and suggestions to Petr Voří¹ek, the PECBMS coordinator, EuroMonitoringbirdlife.cz.
1. National data sources, field work
2. National species trends and indices (some questions apply to the supranational level too)
3. Supranational species trends and indices (some questions apply to multispecies indicators too)
- Does PECBMS check the quality of the national data collected, and how?
- The supra-national species indices and the multispecies indicators are based on adding national results. Is this justified, as the borders between countries are artificial?
- National indices are combined to supranational ones. To this end, missing yearly indices of a particular country (national all-sites totals) are imputed from data of countries within the same region (West, North, East/Central, South, South East). Is it justified to do this? Can we e.g. really expect that data from France can be used to estimate missing values in Spain?
- National indices are weighted when combined according to national population size estimates (BirdLife International, 2004), but the quality of population estimates is very different between countries. Does it mean that weights are based on incorrect values?
- Instead of national population size estimates, other weights may be used in the calculation of supra-national population indices per species, e.g. area of habitat or precision of trend estimates. Why does PECBMS only apply population size estimates?
- Is it possible that early years results are biased towards western Europe, as monitoring schemes started later in many other countries?
4. Multispecies indicators: species selection and classification
5. Multispecies indicators: production
6. Multispecies indicators: interpretation