Cas d’utilisation - Surveillance des papillons

The Swedish Butterfly Network (SBN) has been monitoring the occurrence of butterflies (Lepidoptera) at a series of fixed sites 3-7 times per season on an annual basis since 2009.

This network of observers implements one of two standard protocols at each site: fixed-route Pollard walks or point counts. Butterfly observation information is captured by observers on paper data capture sheets that they send to the national SBN office.

The SBN steering committee would like to start publishing these data online to GBIF in order to strengthen collaborations with the Swedish Environmental Protection Agency, the Swedish Transport Administration, and the Swedish County Administration Boards to influence conservation policies for Lepidoptera in Sweden.

Butterfly monitoring surveys are conducted annually at more than 500 sites by volunteers from 1 April through 30 September. Sites are visited 3-7 times per season. The program does not dictate when sites are surveyed but they provide recommendations (see table below).

The monitoring scheme implements two established methods: fixed-route Pollard walk transects and point site counts. The same method is used at a site each year. These methods are described in Pollard and Yates (1993) and Pettersson et al. (2011 and 2022) and enable the monitoring scheme to assess yearly changes in (1) the number of butterflies seen and (2) species composition.

Fixed-route Pollard walk transects

Fixed-route Pollard walk transects are pre-defined routes typically 0.5-3 km in length. Surveyors follow the transect at a steady pace and identify all the butterflies observed up to 5 m in front, 5 m above, and 2.5 m to each side (see the figure below).

A transect can be any shape, including a loop. Each transect is inventoried once per visit. Some transects are divided into segments that typically represent a change in habitat. For example, a loop that follows a forest road, over a clearing, and then out onto a bog will have three segments. Each segment is inventoried once per visit.

Each survey log from a fixed-route Pollard walk survey will include the following information:

Point site counts

Point site counts cover an area with a 25 m radius and a height of 5 m that are surveyed for 15 minutes per visit. A point location may be completely circular with a radius of 25 meters OR it may have other shapes. Regardless of shape, the same area must be inventoried on each occasion to ensure the inventory is comparable across surveys.

For a circular point site, the surveyor moves about the circular site for the full 15-minute period and records all butterflies that come within the circle up to 5 m above the ground. See figure below.

For a non-circular point site, the surveyor walks about the site for the full 15-minute period and records all butterflies they observe within the area up to 5 m above the ground. See figure below.

Each point site survey will report the following information:

Weather conditions

General weather data are collected at each site at the beginning of each survey. Observers are asked to record information about air temperature, percent sunshine, and wind strength and direction.

The SBN office uses groups of volunteers to digitize the paper logs and produce digital spreadsheets. The spreadsheets are very simple and include three datasheets:

Capture de données

Gestion ds données

Publication de données

Download UC-Practice-exercise-sheet_EN.docx to provide your answers. (2.9 MB)