Butterfly Monitoring Transects  

Monitoring butterfly populations is an important method for measuring changes in the environment as well as the state of habitats for biodiversity. It is also a useful way that both professional ecologists and volunteers can contribute to the conservation of butterflies and other biodiversity. This manual describes how to set up butterfly monitoring by transect, do the counts and report on them. Butterfly Transect Counts are the main sampling method of Butterfly Monitoring Schemes (BMSs). Since the creation of this method by Ernie Pollard in the United Kingdom in 1973 (UK) (for full details of the development of the method, see Pollard and Yates, 1993) it has grown in popularity, particularly in the last decade. Transect counts, also known as Pollard walks, are fixed-routes where butterflies are recorded following easy rules, on a regular basis (ideally weekly) and during good weather conditions. The simplicity of transect counting and the generation of robust data are key to the popularity of the method and its adoption by countries throughout Europe. Butterfly monitoring makes it possible to assess trends in butterfly populations, and to update these on an ongoing, annual, basis. This allows us to track population changes at a local scale as well as across a region, country and even at the European scale. These trends can be used as indicators of the status of biodiversity and to understand the impacts of environmental change. In this way, the Butterfly Monitoring provides regular, standardised data to assess the conservation status of butterflies and produce Butterfly indicators

When establishing a transect, the route should be selected carefully to enable reliable comparisons of butterfly numbers between years. Transects are typically about 1km long and divided into sections that correspond to different habitat areas or separate components of a site. The transect is ideally walked every week during the butterfly season, counting numbers seen within an imaginary box 5m wide, 5m high and 5m ahead of the observer. Transect walks over a season can be shared between different recorders. The Butterfly Transect method requires a regular commitment, with walks ideally made on a weekly basis. The method is not always ideal for surveying species that are difficult to see (e.g. arboreal species) or species that occur in remote locations. In these situations, other methods can be more appropriate for monitoring, for example counting other butterfly stages (eggs or larvae) or conducting timed counts. This manual describes the information needed to set up a butterfly transect. Monitoring butterflies is an interesting and fun way to learn about butterflies and contribute to their conservation

In brief, a transect is a fixed route established at a site where butterflies are recorded, weekly, over a number of years following some basic rules. The majority of transects are chosen by the walker and they decide which route to choose. Some schemes provide advice about areas to record to get even coverage of land cover/ habitat types as well as ensuring that a good range of the species present in a country are sufficiently monitored. Period of the year and frequency Butterfly Monitoring is done during the butterfly season. Depending on which region of Europe you are in, this period will be longer or shorter. In the bulk of Western, Central and Eastern Europe the butterfly season normally starts at the beginning of April and runs until the end of September. In Southern Europe, the season starts in March or even in February. In northern areas, or in mountains, transect counting is typically restricted to between May and August. Transects have to be walked in reasonable weather conditions when butterflies are active (see below). Ideally, they should be walked every week, but if this is not possible, they should be walked as often as possible. If you are not able to conduct counts during the full recording period, try to cover the summer months when butterfly abundance is highest and do the visit every two weeks or ten days. If visits are made less frequently (e.g. every three or more weeks) it is far harder to make accurate calculations of butterfly abundance. Butterfly transects, based on citizen science, have been proven to be an easy and effective method  

Time and Weather Conditions to make standardised counts of adult butterflies, the weather conditions must be suitable for butterfly activity. · Time: Butterflies are more active in the central hours of the day when the sun warms up and allows for the flight of butterflies. That usually means between 3.5 hours before and 3.5 hours after the sun is at its highest point. The best moment for counts depends on where you are in your time zone. In the United Kingdom, counts are best made between 10.30h and 16.30h summertime, in the Netherlands between 10.00h and 17.00h, further east in the Central European Time-zone between 9.30h and 16.30h will be best and in the South of Europe between 9.30h and 17.00h. Under exceptionally hot situations these times can be extended with an extra hour on both sides and in some areas, the central hours of highest temperatures should be avoided in the summer. · Temperature: Only count when the air temperature is 13°C or higher. Between 13 and 17°C it is important that it is sunny with a cloud cover of 50% or less. At temperatures of 18°C or more it is also permissible to count with a higher cloud cover. Try to measure the temperature with a portable thermometer, with a smartphone or from a meteorological website of your region. · Cloud Cover: do an estimation of the clouds that cover the sky in rough percentage. · Wind: it should be 5 or lower on the Beaufort scale (called a fresh breeze), which is when the branches of a moderate size move and small trees in leaf begin to sway. In general, count when the weather is nice and pleasant and the butterflies are active!