BMS methods

On this page you will find explanations for monitored data in eBMS:

  • Transect Counts
  • 15-min Counts


Butterflies, in common with some other groups of insects, have declined in many places in recent decades. We need their monitoring to understand the causes of the decline and to support conservation measures. One of the best networks to get useful information and important results of butterfly monitoring is with citizen science. Thanks to thousands of volunteers we know the status of butterfly species and see where is necessary to apply conservation actions. 

You could help us counting butterflies with different methodologies depending on your preferences. Butterflies can be monitored by anyone who has the time and is willing to learn the butterfly species from their place. There are hundreds of methods to count butterflies but not all of them provide the same information.

There are different types of methodologies where time and standardized methodology are involved depending on the information that you want to get. Methods for butterflies are like the egg counts in the habitat species, Malaise trap, light traps (moths), time counts, or transects. Here we will explain the two methods that we used in eBMS:



Monitored data in eBMS

In eBMS, all the data collected involved a monitoring effort that provides incredible information for the science (species abundance). Monitored data is important and necessary to know the population trends of our species: if we want to know if one specific species is growing or decreasing in numbers, we need to use this type of methodology.

  • You would need to identify the butterfly species name
  • Commit to nature and nature conservation
  • Invest a bit more time than with opportunistic data (just a bit more!)


The basic and more important methodology of eBMS is the transect counts where we get the most robust information on the butterfly population. All the Butterfly Monitoring Schemes are made by many different transects in their country. However, due to the difficulty of applying transects in some countries and remote areas, a new methodology 15-min Counts was created to reinforce ​​​the monitored data and give more flexibility in its collection. With 15-min Counts is expected to increase the butterfly monitored data in Europe, but a BMS should always have as a basis an important number of transects. 


Transect Counts - Pollard Walks

A transect is a fixed route (walk) established at a site where butterflies are recorded, ideally 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 is sufficiently monitored.

You can do the counts as part of a team: it is more fun to share experiences of what you saw and you can replace each other during holidays. There are just a few rules to follow for doing a transect:

  1. Length? Transects are typically about 1km long and divided into sections that correspond to different habitat areas, or are a fixed length (e.g. 50m).
  2. When to count? Butterflies are counted when adults are present - e.g. during the flight period of butterflies. Depending on the country and the region, the flight period of butterflies will be longer or shorter (normally during spring and summer).
  3. Frequency? At least 10 visits per year. The transect is ideally walked every week during the butterfly flight season. If it is not possible, count as often as possible, every two weeks or 10 days. Don't leave more than 3 weeks between one visit and another. If not possible to follow this regime, your visits can be concentrated in a few months (only in spring/summer) to cover the flight period of some species. 
  4. How to count? Count butterfly adults in an imaginary box of 2.5m to each side, 5m high and 5m ahead (see the image). 
  5. Which weather? The visits should be done with good weather: sunny and warm, with no rain and not too windy. Count when butterflies are more active, in the central hours of the day, at least with 13°C if it is sunny or 17°C with cloudiness. See the manual for more explanation regarding the weather. 



Download the Butterfly Transect Counts Manual for more explanations, it is available in several languages: PortuguesePolish (a Manual adaptation for Poland), SpanishItalian and Bulgarian


For registering your transect visit:

  • You can download and print a Field Sheet pdf to bring it to the field
  • Or you can register directly your transect visit with your phone by downloading "ButterflyCount", the eBMS app on your phone (go to the page eBMS- mobile application






15-min Counts 

This type of monitoring is used to obtain butterfly abundances and it has been used for monitoring rare species and butterflies with specific behaviors. This method is basically based on monitoring in a specific area for a fixed amount of time, in eBMS is 15 minutes. We recommend this type of method for people with some knowledge of butterflies that like to visit different areas and habitats. 

Keeping the same time in areas with similar extensions will produce standardised results which you can obtain butterfly abundances. This method is used for butterflies such as Melitaea athalia and Argynnis adippe in the United Kingdom. 

You can use the eBMS app, ButterflyCount especially developed to perform this methodology of 15-min counts. The app records your tracks while counting butterflies for 15 minutes. You will see the time running down with the possibility to pause it while taking pictures or identifying a species. When the time is over the app will let you know vibrating. Discover more information of the ButterflyCount app on the page: eBMS data -> eBMS - mobile application






More information

If you want to have more information on these methodologies, please refer to the Manual for Butterfly Monitoring and the Butterfly Transect Counts Manual. There may be other methods used for butterfly monitoring. For studies on specific species or populations, it may be necessary to adopt more complex methods. Please refer to the list of references below to find more information about other techniques used for butterfly monitoring. 








Nowicki, P., Settele, J., Henry, P. Y., & Woyciechowski, M. (2008). Butterfly monitoring methods: the ideal and the real world. Israel Journal of Ecology and Evolution54(1), 69-88.
Van Swaay, C., Regan, E., Ling, M., Bozhinovska, E., Fernandez, M., Marini-Filho, O.J., Huertas, B., Phon, C.-K., K”orösi, A., Meerman, J., Pe’er, G., Uehara-Prado, M., Sáfián, S., Sam, L., Shuey, J., Taron, D., Terblanche, R., and Underhill, L. (2015). Guidelines for Standardised Global Butterfly Monitoring. Group on Earth Observations Biodiversity Observation Network, Leipzig, Germany.
GEO BON Technical Series 1, 32pp.
Van Swaay, C.A.M., Brereton, T., Kirkland, P. and Warren, M.S. (2012) Manual for Butterfly Monitoring. Report VS2012.010, De Vlinderstichting/Dutch Butterfly Conservation, Butterfly Conservation UK & Butterfly Conservation Europe, Wageningen.
van Swaay, C. A., Nowicki, P., Settele, J., & van Strien, A. J. (2008). Butterfly monitoring in Europe: methods, applications and perspectives. Biodiversity and Conservation17(14), 3455-3469.