Becoming a

 Transect Walker

Are you  thinking about becoming a Transect walker?

Below is a series of  questions from someone who might be interested in contributing and curious to find out more and what is involved in this most rewarding role. 

Did you know on a good summer day up to 70 or more Yorkshire volunteers can be doing transect walks?  Transect recorders form a small army of rarely mentioned conservation heroes working between them about 3000 hours a year here in Yorkshire.  A  recorder who walks every available week of the season (see later) might over a year spend time equivalent to a full working week.  In Yorkshire we cover more than a thousand miles a year and  in the UK transect walkers walk more than the circumference of the earth  a mighty 25,000 miles!  

Why do we monitor?

 Butterflies are the most recorded taxonomic group globally and particularly in the UK. They are also some of the most sensitive species to changes in our climate and their natural  environment and typically undergo large year-year variations and movements as a result. Butterflies (and moths) occupy key positions in ecological communities because their larvae are mostly herbivorous and in turn they are food for other organisms especially birds, provide hosts for invertebrate parasites and act as pollinators. The large dataset we help produce allows scientists internationally, who regard our data as of the highest quality, the gold standard in biological recording, to pick out the effects on abundance and species richness across the UK because of the fine-grained geographic coverage over nearly 40 years of recording.

       The United Kingdom Butterfly Monitoring Scheme (UKBMS) is regarded as the most credible ‘canary in the cage’  of the health of our environment.  This subject is now at the heart of topical debate with governments declaring we are now in a  biodiversity as well as climate  emergency. Each generation ‘resets’ to a much lower ‘norm’ and only the oldest of us  now remember the moth snowstorms in our car headlights or our insect-splattered windshields of summers gone. Our data therefore has an  important role to play, and even more so in the future

Where does the data go? 

Our records provide the essential foundation for  conservation work to help the UK’s declining butterflies. Monitoring shows how butterflies are faring so conservation efforts can be targeted at those most at risk of extinction.  They can help reveal the impact of climate change and other environmental issues on our butterfly populations. They underpin the management of important butterfly sites, help protect habitats through the planning system and enable Butterfly Conservation to produce regular State of the UK’s Butterflies reports, local and national atlases and Red Lists of priority species.  They are extensively used by our government in the annual assessment of biodiversity

Why walk transects?

Transect data has much more scientific validity than casual recording, as the results are more comparable year on year because of the rules under which they are undertaken, which attempt to iron out changes in numbers due to different people recording in different ways. It also takes account of changing weather conditions during a walk. Casual recording or targeted surveys win hands down every time if you want to detect and track rapidly expanding species, However, they are very poor ways to detect declines which the transect methodology tends to pick up better Transects actually started in Yorkshire with Deepdale and Peter Robinson doing the very first in the UK. Some of our transects date back to1970 although I've only looked at the current UKBMS which dates back to 1995. This heritage means some routes have 20 plus years of uninterrupted recording which greatly adds to their value. 

What's involved in doing a transect?

 The Pollard walk is accepted scientifically as producing the most comparable valid indicators.  A fixed route is walked each week from 1st April till end of September, 26 weeks in all,  providing suitable weather conditions are met  during the middle hours of the day 10:45-15:45.  Counting takes place within a 5m by 5m cube immediately in front of the walker. On occasion recorders  walk when the minimum weather conditions are not met. In fact, one of the main issues for recorders is with finding a weather slot. You may walk at 13’C providing it is sunny, and walks are not undertaken if overcast unless temperature is above 17’C. Each transect has 5-15 sections reflecting changes in habitat. Most are around  2km and take about an hour to walk. Sunshine is recorded as a percent of time a shadow is cast on the ground for each section. These same rules apply to WCBS and single-species transects. 

Would you like to know more?

Take a look at our video  which covers identification skills  as well as the  transect walking technique called the Pollard walk HERE or take a look at the Identification presentation opposite.

Find the official guide HERE .  How to input data HERE and the Recording Form HERE 

To start your journey go to UKBMS .

There is an annual get together of  all recorders get a chance to talk about their transects and share experience  see HERE

If you want to know more about where  our transects are and  where we are short see below.

Butterfly Identification for Transects.pptx

Where do we walk? 

 Many of our scarcer species are habitat specialists and are only found in certain woodlands or unimproved grasslands, often on nature reserves, and a transect provides a proven method of monitoring the health of these populations.  More than half of the Yorkshire  transect sites are managed by YWT plus others from RSPB, LNR’s, NNR’s and  NT. These organisations  are instrumental in most of our transects because they want to know how well they are managing their sites. It is often their own volunteers whom we have helped train who carry out the surveys. Transects are also adopted by biodiversity sites but there are many transects in Green spaces  and the wider countryside even verges. 

Coverage is displayed  in a interactive map below  with active transects ticked in green;  those not monitored since 2020 in orange and 2019 or older in red.  

Is there more than one type of Transect?

There are different types of transects for different purposes. All follow a defined route and all species are counted through the flight season on our traditional transects. However there are species  like Pearl Bordered Fritillary, Northern Brown Argus and Large Heath  in a particular habitat which often has little interest outside of its flight period. So to save volunteer effort in often quite difficult terrain single species transects are undertaken, usually  weekly,  for just  the flight season. The third type of transect is the timed count where only a single species is counted for a specified time. These are useful in monitoring some of our more tricky tree canopy species such as Purple or White-letter Hairstreaks which are best recorded by spending 5-10 minutes observing. Short timed counts beneath suitable trees or in glades on woodland transects would be a useful ‘bolt on’ during these species flight seasons greatly adding value. 

How many do we walk?

 There are  more than 150 transects across Yorkshire registered on UKBMS  

Nearly 110 had more than a single walk in 2023 and are shown below. 

 In 2021 nearly 70 were walked while in 2020, during the pandemic  43 transects were walked,  and 49 in 2019

The Target is to reach 140  and cover as many landscapes as possible.  


We need more transects so where are the priorities?

The map below shows areas  of Yorkshire where we really need more  transects.  They include  the North York Moors and Clevelands Hills,  the Wolds , the Magnesian limestone ridge, the Aire, Wharfe and Nidd Valleys , the coal measures and the Dark Peak. The  priority areas contain suggestions for sites. Have a look and see if there is one near you or maybe you know somewhere interesting close by where you live which is within one of the priority area shown below.   In which case do please be in contact  with our transect co-ordinator

NB Volunteers are always needed on the Yorkshire Dales National Park  and on the  North York Moors