Watervogels - Wintering waterbirds in Flanders, Belgium

Study Extent

The bird counts are organized as a regional network “Waterbird counts Flanders” coordinated by the Research Institute for Nature and Forest (INBO). The network divides Flanders, Belgium into 24 regions, each of them with a local coordinator. The fieldwork is mainly done by skilled volunteer birdwatchers, often working together within local bird clubs. The NGO Natuurpunt (http://natuurpunt.be) supports the majority of these bird clubs and volunteers, and thereby delivers an important contribution to the waterbird project. A number of large and important wetland areas are counted by INBO staff (especially in the Scheldt estuary and along the Yser river). To allow reliable comparisons between years and areas, the counts are aimed for maximum standardization. Every winter, birds are counted in six monthly censuses from October to March, on the weekend the closest to the 15th of the month. Counts use the same methodology and are made at 1,000+ predefined locations (see Geographic coverage), covering all kind of wetland habitats in Flanders, such as lakes, ponds, reservoirs, and rivers. Also agricultural areas, often holding large numbers of waterbirds (such as wintering geese), are included. Although the project aims for a (nearly) complete coverage of all areas hosting substantial numbers of waterbirds, this is hard to achieve and the number of counted sites varies between months and years. During counts, numbers of all waterbird species are recorded. This includes divers, grebes, cormorants, herons and allies, swans, geese, ducks, coots and rails. Waders and gulls (optional) have been added on the species list in 1999. Counts of coastal waders are however available since 1992. Through the site http://www.watervogels.inbo.be, volunteers can enter their count and additional data directly into a central database. This database is managed by the INBO and is the source for this dataset.

Sampling

The counts are done at predefined locations, called waterVogelTelgebied. The name of each waterVogelTelgebied is indicated in verbatimLocality, while its ID is indicated in localityID. The polygon shape for most of these localities can be found at http://git.io/vvDVL. The geographic coordinates for the occurrences represent the centroid of the locality (see http://git.io/vvDVR for the procedure). Within the borders of these areas, present waterbird species are counted as completely as possible. Clearly visible areas are often counted from one point with a telescope. Large and less visible areas are usually traversed on foot, by bicycle or by car. A special case are the monthly counts on the Zeeschelde which are performed from boats by INBO staff. The count method (e.g. survey on land) is indicated in samplingProtocol, while the achieved effort (e.g. all waterbirds except geese counted) is indicated in samplingEffort. To reduce the likelihood of birds being double counted or missed, the counts are synchronized as much as possible. Counts are organized on the weekend the closest to the 15th of the month. In large areas with a high probability of local movements, observers are asked to pay special attention to count more or less simultaneously, preferably with multiple observers. Birds are counted during daytime, while specific high tide counts are organized for typical coastal waders (hiding on high tide gather places). The Zeeschelde on the contrary, is mainly counted at low tide due to better visibility of the birds. For some species that are dispersed widely during the day, simultaneous counts on the roost sites are a better alternative for gathering information on their population size. Each winter, supplementary counts are organized for Great Cormorant (since 2003), gulls and Eurasian Curlew. These roost counts are however not included in this database. Keep in mind that covering of the sites differs between months and years. Calculations of trends and population sizes therefore have to deal with missing values.

Quality Control

All records are validated.

Method steps

1. Indicate date, start time and end time (all expressed in eventDate).
2. Indicate observer (recordedBy).
3. Indicate specific count area (verbatimLocality). The area has a unique ID (locationID) and linked higher geography (continent, countryCode, stateProvince, and municipality). Together with the time information, this constitutes a count, which has a unique ID as well (eventID).
4. Indicate count method (samplingProtocol) and achieved effort (samplingEffort).
5. Indicate the count conditions, such as samplingConditions, samplingCoverage, snow, ice, and waterLevel (all expressed as json in eventRemarks).
6. For each observed waterbird species (scientificName), indicate the estimated number of birds (individualCount).
7. Each record gets a GUID, based on the ID assigned by the database (occurrenceID).
8. The locationID is cross referenced with the geospatial information for the localities (http://git.io/vvDVL).
9. Geographic coordinates are calculated based on the centroid of the locality using this methodology: http://git.io/vvDVR. The resulting information is expressed in decimalLatitude, decimalLongitude, geodeticDatum, georeferencedBy, georeferencedDate, georeferenceProtocol, georeferenceSources, georeferenceVerificationStatus, and georeferenceRemarks.
10. Taxonomy information is added based on the scientific name and expressed in kingdom, phylum, class, taxonRank, nomenclaturalCode, and scientificNameAuthorship, as well as an Euring code code (taxonID) and Dutch vernacular name vernacularName.
11. Identification information is added based on the event information: identifiedBy = the observer, dateIdentified = eventDate without time information.
12. Dataset metadata information is added (type, basisOfRecord, language, datasetID, datasetName, institutionCode, ownerInstitutionCode) as well the rights holder (rightsHolder), the license (rights) and data use norms (accessRights).

The term waterbirds is used as defined in the AEWA and thus does not only include species which belong to the order Anseriformes, but all species which are ecologically dependent on wetlands for at least part of their annual cycle. The dataset includes 170 waterbird species (of which 123 are listed by the AEWA) belonging to the following species groups: divers, grebes, cormorants, herons, storks, spoonbills, swans, geese, ducks, coots, rails, cranes, waders, gulls, and terns. Non-native species which have been introduced or escaped are also included. The top 5 of most occurring species, collectively representing one third of the dataset, is Anas platyrhynchos, Fulica atra, Gallinula chloropus, Ardea cinerea, and Phalacrocorax carbo. For all 182 taxa, the Dutch vernacular name is indicated in vernacularName. To allow interoperability with other databases, the Euring code is added in taxonID for all taxa, except for Anas flavirostris, Anas versicolor, Branta sandvicensis, and Chloephaga melanoptera which are not listed by Euring.

1. Animalia
   common name: animals rank: kingdom
2. Chordata
   rank: phylum
3. Aves
   common name: birds rank: class
4. Alcidae
   common name: auks rank: family
5. Anatidae
   common name: ducks, geese & swans rank: family
6. Ardeidae
   common name: herons rank: family
7. Charadriidae
   common name: plovers, dotterels & lapwings rank: family
8. Ciconiidae
   common name: storks rank: family
9. Gaviidae
   common name: divers rank: family
10. Gruidae
    common name: cranes rank: family
11. Haematopodidae
    common name: oystercatchers rank: family
12. Laridae
    common name: gulls rank: family
13. Pelecanidae
    common name: pelicans rank: family
14. Phalacrocoracidae
    common name: cormorants rank: family
15. Phoenicopteridae
    common name: flamingos rank: family
16. Podicipedidae
    common name: grebes rank: family
17. Rallidae
    common name: rails rank: family
18. Recurvirostridae
    common name: avocets & stilts rank: family
19. Scolopacidae
    common name: sandpipers rank: family
20. Stercorariidae
    common name: skuas rank: family
21. Threskiornithidae
    common name: ibises & spoonbills rank: family

The birds were counted at 1,189 predefined locations (waterVogelTelgebieden, figure 1), covering the wetlands and coast of Flanders, Belgium. No birds were counted at sea. These locations are visited regularly during the wintering and migration season (mid-monthly, from October to March). For each occurrence, the code for the waterVogelTelgebied is indicated in localityID. The polygon shape for most of these localities can be found at http://git.io/vvDVL. The geographic coordinates for the occurrences represent the centroid of the locality (see http://git.io/vvDVR for the procedure).