Big Butterfly Count 16-7-2020 to 8-8-2021

Introduction

The butterfly survey in the Sid Valley took place from the 16th of July 2021 to the 8th of August 2021 to run concur- rently with Butterfly Conservation’s Big Butterfly Count (BBC). Each survey is formatted to run for 15 minutes and uses the Big Butterfly Count reporting method via its App. This invaluable citizen science project not only gives a very good picture of the state of butterflies locally and nationally but also gives an indication of the state of insect populations overalli. This survey will act as a base from which further monitoring and support for butterflies can be established in the Sid Valley and as a comparison with the results for 2020. Both these reports can be found on the Sid Valley Biodiver- sity website, https/:sidvalleybiodiversity.org.uk The Big Butterfly Count did not allow for recording uncommon or rare species.

This year 140 counts were completed in the Sid Valley, in comparison with 127 last year. A big thank you to everyone who took part.

The Weather

In the three-week period of the Big Butterfly Count (BBC), the first week had some excellent days of hot sunny weather, often in succession; this period recorded the best butterfly numbers. The second week was particularly wet, unsettled and even stormy and recording was much curtailed at this time. The third week saw mixed weather, butterflies were out but numbers were low, though there were some hot periods on some days. Looking at the chart below, quite a lot of peo- ple were waiting for good weather before they went out and this resulted in the two busy days in the last week.

When and Where

The BBC system of 15-minute observations is a very useable format for most people doing butterfly counts. But when and where you do them is a critical issue. Last year a neighbour mentioned how swarms of butterflies lifted from the ground as her children played on Soldiers Hill. So this year that was one of the first places I went, and counted 91 Meadow Browns within 15 mins. I have no doubt if you set your mind to just this one species on a similar occasion this number could be easily surpassed. Another member of the public recorded 50 Marbled Whites in one observation. Knowing where to look for them I went on a dull evening, not one was flying. In another location near Jacobs Ladder 15 Six Spot Burnets were recorded in one count, that’s nearly half the total for the whole of the Sid Valley over three weeks. Getting to know when and where to make one’s observations is part of the fun of the BBC, and without this knowledge the results could so easily have been different.

Most Notable Changes from 2020

Red Admiral much more abundant generally
Marbled White very successful, especially on the meadows on Soldiers Hill Ringlets made a big improvement
Holly Blues numbers were down
Brimstones numbers were low but this is not their normal season

Overall Results

A comparison of the Sid Valley to National and Devon counts iii

This year saw the Devon results and the Sid Valley results tally, with the meadow species of Meadow Browns and Gate Keepers coming out on top in first and second place. Gardeners will be pleased to note that the Large and Small Whites do not hold the top spot here. What is very encouraging this year is that the Red Admiral made it into the top five slots in the Sid Valley, Devon and nationally. Last year in the Sid Valley it took 9th spot with 25 butterflies spotted, this year it is in 4th place with a stunning 89 individuals spotted, this amounts to an increase in population of two and a half times.iv It is good to see this year the Sid Valley numbers of Red Admirals equate to those in the rest of Devon.

Butterfly Counts per Day

The BBC system of 15-minute observations is a very useable format for most people doing butterfly counts. But when and where you do them is a critical issue. Last year a neighbour mentioned how swarms of butterflies lifted from the ground as her children played on Soldiers Hill. So this year that was one of the first places I went, and counted 91 Meadow Browns within 15 mins. I have no doubt if you set your mind to just this one species on a similar occasion this number could be easily surpassed. Another member of the public recorded 50 Marbled Whites in one observation. Knowing where to look for them I went on a dull evening, not one was flying. In another location near Jacobs Ladder 15 Six Spot Burnets were recorded in one count, that’s nearly half the total for the whole of the Sid Valley over three weeks. Getting to know when and where to make one’s observations is part of the fun of the BBC, and without this knowledge the results could so easily have been different.

 

The Ups and Downs

It is difficult to make any definitive statements about changing butterfly populations in the Sid Valley from just two years figures. Both the weather and the observation methods have too big an influence on the numbers. But there some inter- esting points to highlight. Firstly, the three species highlighted last year as being worryingly low all improved this year. These are Red Admirals, Peacocks and Small Tortoiseshells. These with Commas I consider the ‘beautiful butterflies’ most likely to be seen in parks and gardens, ones that catch our attention most often. The Small Tortoiseshell prefers damper conditions and so this year has suited it better. The meadow butterflies have done well again this year, we have a good range of developing meadows in the Sid Valley and hopefully we will see this habitat grow in quality and quantity in the coming years. Notable this year has been the profusion of Meadow Browns and the locally abundant Marbled Whites. Ringlets which also prefer slightly damper meadow areas have done well; dampness has certainly not been a problem this year! On the low side this year are the Holly Blue, Speckled Wood and Brimstone. I have no explanation for the Holly Blue, one to watch next year. The Speckled Wood I have seen in reasonable numbers this week, one week after the count ended, and the Brimstone is most often seen in the spring after hibernating as an adult, and therefore low numbers at this time of year are not a particular concern.

 

Sid Valley Zone Results

Comments on the Zones

Each of the zones identified in the diagram above offer very different characteristics in terms of habitats and frequency of counts. It is understandable that the majority of the counts are in the coastal areas these being where most people live and exercise. However, the significantly larger areas of the North East and North West will have interesting habitats that need further exploring. The Byes did particularly well for the ‘beautiful butterflies’, Knapp Copse is a haven in the North East. The North West is a little under represented, and with locations such as Fire Beacon hill and Core Copse it could be targeted more effectively next year. Mutters Moor has good butterfly populations and with Jacobs Ladder and the fields up to Peak Hill the West Coast area is well populated. Numbers of butterflies are lower in West Town but with 15 species represented it has a very good diversity, and has the best numbers of Holly Blues. As last year, the survey suggests the Holy Blue is more abundant in the urban areas while it is the Common Blue that is more abundant in rural areas. The East Coast with its extensive meadows generates the highest counts.

Habitats of Particular Note

Mutters Moor: Pebblebed Heath, particularly good for Grayling, all observations of this species were here

Knapp Copse: especially the Mire where Brimstone, Silver Washed Fritilary, Red Admiral, Peacock and Green Veined White all had good numbers, the Green Veined White benefiting from the damp conditions

Alma Meadow: Flower Rich Meadow, at the time of the count the Birds-foot-trefoil was abundant favouring the Com- mon Blue

Soldiers Hill: Meadow,very good counts of Marbled White amongst the other meadow butterflies
Lincombe: Cliff Meadow, the richness of the flora indicated this as a particularly good spot to study in more depth

Jacobs ladder and the fields ascending westwards: the established and developing wild flowers of this area are nota- ble, the birds foot trefoil supporting the Six Spot Burnet.

Charles Sinclair, 19-8-2020

i Comments from ‘Silent Summer’, Chapter 24 Butterflies by J A Thomas. ‘Worldwide butterflies are the most studied insect group by a large mar- gin and the availability of material means they can be used effectively to determine the health of ecological systems. In total there are 59 UK species of butterfly out of a worldwide number of 20,000 species. The average rate of decline of butterfly species in the British Isles has been high in recent decades, exceeding that of breeding birds or native vascular plants.’

ii If you take into consideration the total number of butterflies counted each year there is a 26% increase this year. Increasing the number of butterflies counted last year by 26% and then reducing by 10% to account for the increase in number of counts this year has led to the compara- tive figures.

iii The BBC only collate information on the top five butterfly species in any geographical area so I will confine my comments to these both nation- ally and in Devon. For the remaining 15 species the information has had to be manually taken from the BBC maps, and therefore numbers are only taken for The Sid Valley.

Background Information