This core indicator evaluates the status of abundance of wintering waterbirds in the Baltic Sea region. The wintering waterbirds are considered to reflect good status when at least 75% of the considered species deviate less than 30% downwards (species laying more than one egg per year) or 20% downwards (species laying one egg per year) from the baseline condition during the reference period 1991-2000.
Key message figure 1. Status of the indicator 'abundance of waterbirds in the wintering season'. The assessment is only carried out for coastal areas (not offshore). Since harmonized offshore monitoring could not be conducted for this assessment period and several species show strong declines in the whole offshore area (Skov et al. 2011), an overall assessment of birds is not possible and the data and results are based only on land based observations. The assessment is for the entire Baltic Sea – including all species currently assessed (top left, Scale 1 HELCOM assessment units, defined in the HELCOM Monitoring and Assessment Strategy Attachment 4) and for seven sudivisions of the Baltic Sea (see Assessment unit figure 1). Results for the species groups are based on the trends of individual species: surface feeders (top middle), pelagic feeders (top right), benthic feeders (bottom left), wading feeders (bottom middle) and grazing feeders (bottom right). NOTE: due to the size of figures within the composite image details in some coastal areas are better visualised via the HELCOM Map and Data Service (MADS). Click here to access interactive at the HELCOM Map and Data Service: Abundance of waterbirds in the breeding season, surface feeders, pelagic feeders, benthic feeders, wading feeders, grazing feeders.
The assessment is only carried out for coastal areas (not offshore). Since harmonized offshore monitoring could not be conducted for this assessment period and several species show strong declines in the whole offshore area (Skov et al. 2011), an overall assessment of birds is not possible and the data and results are based only on land based observations.
The current evaluation is based on data from coastal surveys of 22 waterbird species for the assessment period 2011-2016. Waterbirds wintering in offshore parts of the Baltic are currently not represented in the indicator due to lacking data, but the inclusion of those birds is under development with the aim to have data from offshore surveys included by 2019.
In the period 2011-2016, the abundance of wintering waterbirds in the Baltic Sea was in a good status, because 82% of the species assessed achieved the threshold value (at least 75% of species meeting threshold value indicates good status). The evaluation could be applied to five species groups of which three groups, namely surface feeders, pelagic feeders and wading feeders, achieved good status (≥75% of species meeting threshold value), whereas benthic feeders and grazing feeders did not reach the threshold value. These assessments only reflect the status of coastal waters, because waterbird species wintering predominantly in the open sea are not considered.
The indicator was also applied to seven subdivisions (aggregations of up to four sub-basins). A good status of wintering waterbirds was observed in four of the subdivisions (Bornholm Group, Gotland Group. Gulf of Finland, Bothnian Group, but could not be achieved in three subdivisions (Kattegat, Belt Group, Aland Group). Subdivision assessments for species groups mostly reflect the same pattern as the overall assessment, but showed more variation.
The confidence of the evaluations is estimated to be intermediate.
The indicator is applicable in the waters of all the countries bordering the Baltic Sea.
As predators at high levels in the food web, but also as herbivores that may remove large proportions of macrophytes by grazing, waterbirds are an integral part of the Baltic marine ecosystem.
The indicator follows temporal changes in the abundance of key waterbird species, which have functional significance in the marine ecosystem and respond to numerous pressures, many of them caused by human activities. Thus, the indicator gives an overall view of the state of marine birds in the Baltic Sea and reflects the cumulative impact of pressures.
D1C2 The population abundance of the species is not adversely affected due to anthropogenic pressures, such that its long-term viability is ensured.
D1C4 The species distributional range, where relevant, pattern is in line with prevailing physiographic and climatic conditions.
D4C1 The diversity of the trophic guild is not adversely affected due to anthropogenic pressures.D4C2 The balance of total abundance between the trophic guilds is not adversely affected due to anthropogenic pressures.
HELCOM (2018). Abundance of waterbirds in the wintering season. HELCOM core indicator report. Online. [Date Viewed], [Web link].
Abundance of waterbirds in the wintering season HELCOM core indicator 2018 (pdf)