The Big Butterfly Count is a citizen science project organised by Butterfly Conservation for the last week of July and the first week of August each year. Over the last two weeks nature lovers all over the country have been taking part.
On a sunny day, yes there were a few, people stopped for 15 minutes to count how many butterflies from a list of 20 species they could see. All 20 species on the list are Lepidoptera but two are day flying moths, the 6-spot Burnet and the Silver Y. For convenience, this report will include them in the general term butterflies.
The Big Butterfly Count is more or less finished and we are starting to look at the results for Sidmouth. Nationally, more than 92,000 citizen scientists carried out more than 130,000 counts and recorded more than a million and a half butterflies. Locally, just over 100 volunteers made over 160 counts and recorded more than 2,500 butterflies.
The count is a snapshot, what can be seen in a fifteen-minute slot has an element of chance, but this is ironed out if you have enough counts. The national sample is certainly large enough for researchers to draw robust conclusions and Butterfly Conservation’s report will be published later this year. The 160 counts in our valley allow us to make some general comments.
Compared to the rest of the country, Sidmouth comes out well. Within the boundary of the Sidmouth administrative area, bounded roughly by Weston, Mutters Moor and Putts Corner, we had more butterflies per 15-minute count than the national average, 16.5 butterflies per count compared to 11.9 nationally.
Our top 5 species, accounting for nearly 3/4 of the total recorded, were:
- Gatekeeper 623,
- Meadow Brown 403
- Red Admiral 365
- Large White 279
- Peacock 276
Perhaps unsurprisingly, on average nearly twice as many butterflies were found by volunteers counting in the countryside than in town, 22.1 per count compared to 12.8 per count. Some gardens had very high counts but most of these were on the edge of town with open fields very close by.
The highest individual count was 76 on Peak Hill but that included a swarm of 6-spot Burnets that were clustered on the few remaining flowers left after some of the area had been strimmed. Perhaps more representative were the two counts on Core Hill (57 of 4 different species) and Fire Beacon Hill (56 of 6 species). There were 2 counts that recorded no butterflies in the 15 minutes, a town garden and a count on Peak Hill.
Of course, different butterflies prefer different habitats. Gatekeepers were the most common in both town and country areas, but Meadow Browns really are a countryside species, the clue is in the name. Meadow Browns dropped to fourth in the town counts, Red Admirals and Large Whites leapfrogging up to 2nd and 3rd.
Dividing the count locations roughly into urban and rural, the top 5 were:
Rural 67 counts Urban 100 counts
- Gatekeeper 314 (4.7) Gatekeeper 294 (2.94)
- Meadow Brown 235 (3.5) Red Admiral 185 (1.85)
- Red Admiral 188 (2.8) Large White 165 (1.65)
- Large White 163 (2.4) Meadow Brown 162 (1.62)
- Peacock 178 (2.7) Peacock 137 (1.37)
To allow a comparison between the two sets of data, figures in brackets are the average number of butterflies per count.
The sites are in simple categories including fields, gardens, woods and public parks. Of the top 20 sites in the local survey, 10 were fields with an average of 51 butterflies per count, 3 were gardens with an average count of 47, 3 were woodland glades with an average of 41 butterflies per count.
As we are interested in biodiversity, a simple biodiversity factor (BF) of the number of butterflies multiplied by the number of species was applied. Although the Peak Hill site had the highest total count at 76, as nearly all of these were a single species the BF is only ranked 23rd in the list with 228 while the Fire Beacon Hill site with 56 butterflies of 6 species has a BF of 336, but that is still only ranked at number 13.
The highest BF was a field on the coast path above Weston Mouth with 52 butterflies but of 13 species from the project’s list of 20. It was even more diverse because other species such Small and Large Skippers, Wall Browns and Cinnabar were observed but not recorded because they are not on the list specified for the study. This field has a lot of butterfly favourite flowers such as Knapweed, Thistles and Wild Carrot but, as important, food plants for the caterpillars. The Marbled Whites and Large Whites have been observed to be actively egg laying earlier in the year.
As well as having more butterflies, the field sites were more diverse than the garden sites. Of the 6 sites with more than 10 species recorded, 4 were fields and 2 were gardens.
The mean BF for fields was 160 with a range of 0-676. The mean BF for garden sites was only 66 (41% of the BF for field sites) with a range from 0-429, the highest was a large garden in Bickwell Valley very close to open fields.
A small number of very diverse sites skews the mean, but this is more pronounced in the gardens than the fields. The median for garden sites is just over half the mean at only 38. The median for the field sites is ¾ of the mean and 3x the BF median for gardens at 120.
After fields and gardens, the third largest category is public parks and gardens with 16 sites. These range from the barren Long Park to Connaught Gardens and the most productive sites of the golf course and community orchard in The Byes. On average, these sites were even poorer than the private gardens with a mean BF of only 35. This is boosted by the two rich sites and the median is only 14.
More detailed analysis will be appearing on the SVBG website in the coming weeks. In the meantime, what can we do to help butterflies make their home among us?
If you have a garden, the answer is simple, have as much variety in your garden as you can. Have lots of flowers, but not just the cultivated ones like the Buddleia Butterfly Bush. Make room for a few wild flowers, many butterflies love Knapweed and Thistles.
Of course, if you want butterflies, you have to have somewhere for them to lay their eggs and for the caterpillars to feed. Peacocks and Red Admirals love Buddleia but their caterpillars rely on nettles. There was an explosion of butterflies in cities after the war as bomb sites were left to nature.
Our number one, the Gatekeeper, loves Bramble, but the caterpillars feed at the base of long grass so, if you left some of your lawn to grow this summer, please leave it until September to give the caterpillars a chance to tunnel underground where they pupate and hibernate. Who knows, next year we might beat this year’s Big Butterfly Count.
The Big Butterfly Count is a citizen science project organised by Butterfly Conservation for the last week of July and the first week of August each year.
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