Meetnetten.be - Transects for dragonflies in Flanders, Belgium

Study Extent

1. Calopteryx virgo (Beautiful Demoiselle / Bosbeekjuffer) occurs near oxygen rich watercourses with good water quality and riverbank that mostly consist of trees and bushes. The males exhibit territorial behaviour over a 5 m stretch of sunlit water/riverbank. In Flanders it is widely distributed in the eastern half of the region. 2. Coenagrion pulchellum (Variable Damselfly / Variabele waterjuffer) occurs mainly in moderately to nutrient-rich pools and ponds characterized by well-developed aquatic and riparian vegetation. Although it is scarcely distributed all over Flanders, it shows a clear preference for the valley of the river Scheldt and its major tributaries. 3. Aeshna isoceles (Green-eyed Hawker / Vroege glazenmaker) occurs in moderately to nutrient-rich pools and ponds. It can also be found in nutrient-rich fens. The riparian vegetation is well developed and reed or bulrush is mostly present. The species has seen a strong increase and expansion in Flanders over the last 10 years and shows a clear preference for the major river valleys and areas with high densities of pools..

Sampling

Sampling was done using the protocol described in De Knijf et al. (2019) and explained to volunteers in Ledegen et al. (2017). 1. Calopteryx virgo (Beautiful demoiselle / Bosbeekjuffer): a sample of 30 populations is monitored, of which 10 are counted each year. In the year a population is counted, at least three transect counts are carried out when flying adults occur (May 20 - Aug 20), with good dragonfly weather, between 11h and 16:30h. A transect is located along the shore and is at least 100m, maximum 500m long (depending on the amount of suitable habitat). During a count, the transect is walked slowly and all adults are counted up to a distance of 2 m on the bank and 3 m above the water. 2. Coenagrion pulchellum (Variable Damselfly / Variabele waterjuffer): a sample of 30 populations is monitored, of which 10 are counted each year. In the year a population is counted, at least two transect counts are carried out when flying adults occur (May-June), in good dragonfly weather, between 11h and 16:30h. A transect is located along the shore and is about 100 m long (depending on the amount of suitable habitat). During a count, the transect is walked slowly and all adults are counted up to a distance of 2 m on the bank and 3 m above the water. 3. Aeshna isoceles (Green-eyed Hawker / Vroege glazenmaker): a sample of 30 populations is monitored, of which 10 are counted each year. In the year a population is counted, at least two transect counts are carried out when flying adults occur (20 May - 30 June), with good dragonfly weather, between 11h and 16:30h. A transect is located along the shore and is about 100 m long (up to a maximum of 500 m depending on the amount of suitable habitat). During a count, the transect is walked slowly and all adults are counted up to a distance of 2 m on the bank and 5 m above the water.

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 dragonfly species for Meetnetten.be are listed at https://meetnetten.be/#group-6. Other dragonflies observed during the sampling are also included. This dataset covers the transect protocol, for which there are 3 target species.

1. Animalia
   rank: kingdom
2. Arthropoda
   rank: phylum
3. Insecta
   rank: class
4. Odonata
   rank: order
5. Calopteryx virgo
   common name: Beautiful Demoiselle / Bosbeekjuffer rank: species
6. Coenagrion pulchellum
   common name: Variable Damselfly / Variabele waterjuffer rank: species
7. Aeshna isoceles
   common name: Green-eyed Hawker / Vroege glazenmaker rank: species

Flanders, Belgium