Meetnetten.be - Site counts for butterflies in Flanders, Belgium

Study Extent

For two butterfly species in Meetnetten.be (Apatura iris and Satyrium ilicis) the choice was made to count these by site rather than transect. This is because these species are mainly found in lower quantities and it would be too likely to be missed in a transect count. 1. Apature iris (purple emperor / grote weerschijnvlinder) is undoubtedly one of the most spectacular butterflies in Flanders. It is a forest species that lives in tree canopies and is not always easy to find. This summer butterfly is followed up at about ten locations each year. Because the butterflies often fly high, they are counted along a fixed route (but not per section or within an imaginary cage). 2. Satyrium ilicis (ilex hairstreak / bruine eikenpage) is in sharp decline in Flanders. Mapping this decline is not evident: in its habitat (forest edges and heathland with scattered small oaks) the species often hides well. We count this species by means of an area census instead of a classical transect census.

Sampling

Sampling was done using the protocol described in Maes et al. (2019) and explained to volunteers in Ledegen et al. (2018). A site count is similar to a transect in that is it visited multiple times, but unlike a transect it is not divided into different sections. A route is mapped out in such a way that observers pass potentially interesting locations and that it can be walked in about an hour. 1. Apature iris (purple emperor / grote weerschijnvlinder): observation locations are recorded and per route the maximum number of butterflies seen at the same time is noted. Also, for each count, the duration of the search is noted. Three censuses are performed between 10 June and 20 July. 2. Satyrium ilicis (ilex hairstreak / bruine eikenpage): counted along a fixed route, but not divided into sections: butterflies that fly further than 5 m are also counted. Each observed butterfly is recorded. The count takes place three times between the beginning of June and mid-July, at 13 counting areas.

Quality Control

Data are collected using a predefined sampling protocol.

Method steps

1. Researchers from INBO and Natuurpunt Studie define and document the appropriate sampling protocol for the target species.
2. Fieldwork is planned and coordinated by Natuurpunt Studie, using https://meetnetten.be.
3. Data are collected in the field by specialized volunteers, using the predefined sampling protocol.
4. Volunteers enter the collected data in https://meetnetten.be.
5. A custom SQL view is created in the meetnetten.be database to map the original data to Darwin Core as an event core, occurrence extension and measurement or fact extension.
6. The Darwin Core views are connected to the INBO IPT and documented with metadata.
7. The dataset is published and registered with GBIF.

The target butterfly species for Meetnetten.be are listed at https://meetnetten.be/#group-4. Other butterflies observed during the sampling are also included. This dataset covers the site count protocol, for which the target species are Apature iris (purple emperor / grote weerschijnvlinder) and Satyrium ilicis (ilex hairstreak / bruine eikenpage).

1. Animalia
   common name: animals rank: kingdom
2. Arthropoda
   rank: phylum
3. Insecta
   common name: insects rank: class
4. Lepidoptera
   common name: butterflies rank: order
5. Apature iris
   common name: purple emperor / grote weerschijnvlinder rank: species
6. Satyrium ilicis
   common name: ilex hairstreak / bruine eikenpage rank: species

Flanders, Belgium