Waterbird indicator for oligotrophic and eutrophic habitats

Multispecies waterbird indicators for oligotrophic and eutrophic habitats. Includes annual indices and smoothed trends. Trends are scaled so that both indicators have value 100 in 1995.

## Data quality description
Published indicator values. Raw data (waterbird pair counts) is collected by volunteers. Indicators are calculated from curated data set with published methodology.

## Methods
Raw data (waterbird pair counts) is collected by volunteers. Indicators are calculated from curated pair count data set with methodology previously published by Lehikoinen et al. 2016 and Soldaat et al. 2017. Indicator of oligotrophic habitats was calculated using the habitat and species specific indicators of Anas platyrhynchos, Anas crecca, Mareca penelope, Bucephala clangula and Cygnus cygnus and the indicators of species that are found almost solely from oligotrophic habitats (Mergus merganser, Mergus serrator and Gavia arctica). Indicator of eutrophic habitats was calculated using the habitat and species specific indicators of Anas platyrhynchos, Anas crecca, Mareca penelope, Bucephala clangula and Cygnus cygnus and the indicators of species that are found almost solely from eutrophic habitats (Spatula clypeata, Anas acuta, Aythya ferina, Podiceps cristatus, Podiceps grisegena, Podiceps auratus and Fulica atra). References: Lehikoinen et al. 2016: Animal Conservation 19: 88–95., Soldaat et al. 2017: Ecological Indicators, 81: 340–347.