Butterfly Monitoring and Recording

Butterfly Monitoring and Recording

Dave Robinson

Volunteer recorder Dave Robinson shares his insights on butterfly recording in Leicestershire and Rutland, some of the species he has spotted and why it is important.

It is early May - the birds are singing, the air is heavy with the scent of blossom, and fresh English asparagus is in the shops.  Our gardens and flower beds are coming alive with the buzzing of bees and the fluttering of butterfly wings.  At this time of year, the butterfly survey season is normally well underway but alas, this year, things are suspended because of the coronavirus outbreak. However – we can still all contribute in a meaningful way to our growing knowledge of these delightful insects!

The monitoring of butterfly populations serves many important purposes.  It gives us a window into the effects of environmental change such as the intensification of farming practices, forestry management, urban development and climate warming.  Although, over one season, it is hard to tease these effects apart, over the longer timescale patterns and trends begin to emerge.  The observations can then help to steer wildlife organisations in the management of reserves, and aid local authorities and farmers in the sympathetic care of our countryside and wildlife.

The annual butterfly surveying activities normally commence during the week starting April 1st, and in line with the Field Guidance notes from the UK Butterfly Monitoring Scheme (UKBMS), continue on a weekly basis until the end of September.  The methodology involves walking a standard “sectioned” route, counting the numbers of each species of butterfly seen within a 5-meter cube – ie 2.5 meters each side and 5 meters in front of the recorder.  It is important that the recording technique is consistent so that results can be compared across differing time periods.  Survey results are sent to the County Butterfly Recorder who populates the appropriate national database.

Leicestershire and Rutland Wildlife Trust co-ordinates many surveys across our two counties including some private landowner sites as well as on Trust reserves such as Charnwood Lodge.  On the latter reserve, two standard surveys are carried out by a team of enthusiastic volunteers.  One takes in the Colony Reservoir, and a second one covers the somewhat different habitat of Timberwood Hill. Both support important local populations of the Small Heath and the Green Hairstreak butterflies. The lower regions of the Timberwood Hill circuit have colonies of the less common Purple Hairstreak.

Green Hairstreak

Green Hairstreak  - Dave Robinson

Nationally, 2019 turned out to be an excellent year for butterflies – the best year since 1997!  Overall numbers of butterflies on the Colony Reservoir Transect held up in comparison with 2018.  2020 would have been the third year of monitoring this route.  Available data for 2018 and 2019 are shown in the link below, with significant increases and decreases in species populations highlighted in green and red respectively. It is interesting to note that many of the population changes mirror the UK national picture. For example, Meadow Brown numbers on the transect were up by around 100% (+38% nationally), and Speckled Wood numbers were down by 29% (-26% nationally).  However, UK populations for the Small Heath held steady at +5%, whereas unfortunately the Reservoir Transect numbers of this insect dropped by 46%. It is only over the longer time scale that the statistical and environmental significance of these numbers can be assessed.

In addition to the regular, formal transect circuits, Leicestershire and Rutland Wildlife Trust volunteers (and staff) regularly make anecdotal recordings of butterflies seen whilst pursuing other activities on the reserves.  During 2019, species such as Silver-washed Fritillary, Dingy Skipper and even Purple Emperor have been sighted at Charnwood Lodge – it is then sometimes frustrating that these observations cannot be recorded as part of the standard transect!

Dingy skipper

Dingy Skipper - Amy Lewis

As well as providing important scientific data, these surveys are extremely enjoyable to carry out! They provide an opportunity to take in some fresh air and exercise and the comradery between the like-minded participants is particularly stimulating. The sharp eyes of the recording team regularly spot other forms of wildlife in addition to the butterflies.  Tree Pipits are regularly seen during the transects, and Wheatears have put in an occasional appearance.  Foxes and Muntjac deer are amongst the mammals which have been seen, and during the summer, the Reservoir is alive with dragonflies such as Brown and Migrant Hawker, Four-spotted Chaser and Black-tailed Skimmer. Needless to say, not one of these observations is allowed to detract from the main objective of butterfly spotting!

Day-flying moths are another group of lepidoptera that are routinely recorded during the butterfly transects.  Brown Silver-lines are probably the most commonly seen species of macro-moth, but occasionally, from late May until early July, the recorders come across the beautiful Forester Moth – a wonderful insect with blue/green iridescent wings which feeds on Common and Sheep’s Sorrel.  Charnwood Lodge has a healthy population of this relatively uncommon species. Common micro-moths which are regularly seen include the Green Longhorn and Mother of Pearl.

Forester Moth

Forester Moth - Dave Robinson

In spite of the coronavirus problems, we can hopefully anticipate that our local grassy areas and gardens will be host to a good number of butterflies over the coming months.  We can all use our hours of “confinement” to record any sightings of these truly beautiful insects and record them on the Butterfly Conservation's Garden Butterfly Survey. All information submitted will be included in the Leicestershire and Rutland butterfly database for the 2020 season. 

As soon as the coronavirus restrictions are lifted, allowing us once more to venture freely into the countryside, the Charnwood Lodge (and other) butterfly monitoring programmes will be able to re-commence.  Plans are in hand to not only continue with the standard transect routes, but to also make special excursions to seek out those less-common butterflies which have only previously been reported on an anecdotal basis.  Indeed, some UK species, such as the Marbled White, are now rapidly expanding their range - perhaps due to climate change - and may well appear on our report forms before too long!

If you are interested in taking part in carrying out butterfly surveys in the Charnwood Forest in the future, we would like to hear from you. There are opportunities to support a small team of volunteers. Don’t worry if you feel your butterfly identification skills are not good enough. Butterflies are not too difficult to learn and you will be given training. Please contact info@lrwt.org.uk 

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