Dutch Centre For Field Ornithology (SOVON) - Bird Atlas 1978-1983 - metadata

Study Extent

The Netherlands, 1978-1983. Thousands of amateur birdwatchers were involved inmapping the distribution of bird species in the Netherlands. The extent of the survey can best be described with the aid of some figures. The total number of observers involved in de survey probably surpassed 5000. They sent in 220000 recordingcards with a total of 5000000 observations of 426 species and subspecies.

Sampling

Month after throughout the year for 60 successive months the recorded the occurrence of the species using a grid of 5 x 5 kilometer squares.In establishing the occurrence of bird species in the squares, two categories were distinguished. 1. birds making use of the terrain (code G) and 2. birds flying over the terrain (code F). In many squares, code G was often accompanied by the corresponding numbers observed.

Quality Control

District coordinators checked all recording cards before they were processed. Afterwards the observers checked their results and reported missing species or other mistakes to the district coordinators. Based on the results distribution maps made. With the use of this distribution maps further checks on unlikely estimates and mistakes in determination has taken place.

Method steps

1. 1. Observation of all bird species in the Netherlands in 5x5 km squares. 2. Extensive checks on the accuracy of the information 3. Distrubutions maps of the occurence of 338 species where made

1. Avis
   common name: Vogels rank: class

The Netherlands