Trend of breeding birds: trend rating

This table gives an overview of the trends of all native bird species regularly in the Netherlands for which a reliable national trend can be calculated. This table also contains the (metric) average trend of all species listed in this table. Trends are shown over a period from 1990 or from the year after 1990 on which reliable counts of the species concerned are available. Trends have also been shown over the last 12 years. The national trend of breeding birds is based on different types of sample counts whose data are combined. The basis of the census is territorial mapping at measuring points of approximately 50-200 ha, with territories of breeding pairs being determined by repeated visits of the measuring points in the breeding season. However, there are also additional methods for species for which this method is less or unsuitable, e.g. point counts for urban birds. Trends are presented in this table using the trend classification. This is determined over a series of years using the annual indices of the species. Indices per year have a broad margin of reliability, which makes it impossible to conclude simply whether some type has increased or decreased significantly. Whether the population of a species has increased or decreased is therefore calculated separately over the entire series of years and the most recent period of 12 years. The increase or decrease is then classified as strong if the average annual change is more than 5 % or moderate if the change can also be less than 5 %. If no increase or decrease can be demonstrated but the average annual change is less or equal to 5 %, it shall be assessed as stable. If no increase or decrease can be demonstrated and the trend cannot be considered stable, it is classified as uncertain. Indices per year are presented in a separate table (see paragraph 3. Links to relevant tables and articles). Status of the figures: Every year, new counting data are made available that are processed in the (re-)calculation of trends. Due to these added annual figures and possible follow-up of counting data from previous years, the trend classifications for updates can change. This may be the case in particular for the trend classification over the last 12 years, as the period for which the calculation takes place is shifting. Changes as of 10 November 2021: Index values of the year 2019 and 2020 have been added. Seven additional species (European Canary, Graszanger, Houtsnip, Kleinst Waterhoen, Cranevogel, Oehoe and Witwangstern) have been included, as the counts of these now yield reliable trends. Changes as of 26 June 2020: In 2019, trends were given over a period of 10 years instead of 12 years. 12 years have been chosen because it includes 2 full reporting periods, which have to be reported under the EU Birds Directive. The data of the Great Yellow Mercury Tail and the great Canadian goose have been mistakenly exchanged. Because the large Canadian goose is an exotic in the Netherlands, it should not be included in the table ‘trend of the Dutch breeding birds’ and has therefore been removed from the list. The large yellow mercury tail, on the other hand, is now included. When are new figures coming? The table is updated annually. The next update will be released in October 2022.