Coastal birds in the Gulf of Bothnia (Kustfåglar i Bottniska Viken)

Study Extent

Selection of study sites: When developing the subprogramme, the study area was covered by a 2x2km grid in which survey squares were clumped into blocks of four adjoining squares. Squares included in the programme contain at least one island. The mainland is not included in the survey. At the start of the programme, a number of so called permanent blocks were surveyed every year. Each year, a number of blocks were randomly selected and added to the survey that particular year. After a method evaluation in 2014 and in concurrence with the start-up of a national coastal bird monitoring scheme in 2015, the strategy for site selection was changed. From 2015 no sites are randomly selected. Instead, all permanent blocks from 2010-2014 have been kept and are surveyed on a 4 year rotation. In addition, the national squares (also 2x2km) that lie within the study area are surveyed yearly. Number of study sites: 2010-2014: In total 114 blocks (453 squares). In Norrbotten 33 blocks (133 squares), and in each of the other three counties 27 blocks (107 squares). Note: Västernorrland and Västerbotten did not join the programme until 2011. 2015-ongoing: In total 65 national squares plus 28,5 blocks (114 squares). In Norrbotten 26 national squares + 8,25 regional blocks, Västerbotten 15 national squares + 6,75 regional blocks, Västernorrland 13 national squares + 6,75 regional blocks, Gävleborg 11 national squares + 6,75 regional blocks. Timing and frequency: Surveys are carried out once per site each year (25 May-25 June), with different time periods northwards along the coast, allowing for differences in start of the breeding season: Gävleborg 25/5-10/6, Västernorrland 1-15/6, Västerbotten 5-20/6, Norrbotten 10-25/6.

Sampling

In each survey square bird observations are registered per counting zone, where a counting zone is an island (or a group of islands in close proximity to each other) and the 100m buffer of sea surrounding the island. Surveys are generally carried out by boat, but bare islands (i.e. without trees) are surveyed by going ashore (weather conditions allowing). Only the area of a counting zone that lies within the square boundaries is surveyed. Species, numbers and breeding activity of birds observed is registered, as well as age and sex when possible.

Quality Control

Confidence in the data is good. All data are checked and validated by the surveyors.

Method steps

1. See Sampling description.

Bird species that breed in coastal and archipelagic environments within the following groups are surveyed: Ducks, geese and swans (Anatidae) Grebes (Podicipedidae) Divers (Gaviidae) Waders, gulls and auks (Charadriiformes) Herons (Ardeidae) The following species are also included in the survey: Rock pipit (Anthus petrosus) Great cormorant (Phalacrocorax carbo) Eurasian coot (Fulica atra) Common crane (Grus grus) Osprey (Pandion haliaetus) White-tailed eagle (Haliaeetus albicilla) Species with a security class 3 or higher (according to the Swedish species information centre (Artdatabanken)) are not shown in this dataset at present. Currently these species are osprey (Pandion haliaetus), white-tailed eagle (Haliaeetus albicilla) and red-throated loon (Gavia stellata). Pulli are not counted, except for common eider pulli from 2020 onwards.

1. Aves
   common name: Birds rank: class
2. Animalia
   common name: Animals rank: kingdom
3. Chordata
   common name: Chordates rank: phylum

All data is collected along the coastline of the four counties of Norrbotten, Västerbotten, Västernorrland and Gävleborg on the Swedish side of the Gulf of Bothnia.