2024 Small Tortoiseshell abundance & distribution

[David Lazarus]

Yesterday, Saturday 21st September, I saw my first Small Tortoiseshell since the 15th July on my local patch in Baddow Meads/Meadgate which is in Chelmsford within mid-Essex. Since July, I have only seen one other Small Tortoiseshell at Wallasea Island on the 29th August. It was such a surprise encounter that it got me thinking. How many have I seen this year and where have I seen them?

As many of you know, I collect sighting records and carry out site surveys within numerous places across the Vice-counties of South & North Essex only. I also target species of concern within Essex, especially those which are threatened with local extinction ~ we might actually say the Heath Fritillary is threatened with extinction within the whole of the UK.

So, I have collected all my available data, which is very frustrating because they are not in one place - for me, a reason for stopping my transect walks in favour of site surveying/targeting species which would mean I could access all my data in one place in real time. The Butterflies of the New Millennium also allows me to present the data in a much more readable form as shown below.

2024 Small Tortoiseshell sightings source: BNM
South & North Essex; local area

Small Tortoiseshell sightings source: UKBMS
Baddow Meads transect

Surprisingly. because it does not feel like it, I have seen 89 Small Tortoiseshell within South & North Essex [I have duplicated Saturday's sighting to add the location on the distribution map]. Obviously, the vast majority of my sightings have been within Baddow Meads/Meadgate - my local patch. And this does not just reflect the fact that I live here and walk around it more often. It is in fact an area of perfect habitat for each of the life stages of the Small Tortoiseshell - this species would be expected to be seen in their 100s, at least 10s, rather than as a single specimen along the River Chelmer and spreading out to the rest of Chelmsford and mid-Essex.

The 2024 abundance for Baddow Meads according to my sighting records only amounts to 83 and I can add a couple more seen at the Chelmer Valley Local Nature Reserve and at Broomfield also along the River Chelmer but in north Chelmsford rather than in the east where I live.

So, 85 Small Tortoiseshell recorded in Chelmsford along the River Chelmer and it's flood plain.

That leaves just 4 during those times that I have visited other sites throughout the whole of Essex in 2024. And there have been numerous occasions at multiple sites -

just 4 Small Tortoiseshell recorded at all other sites visited throughout South & North Essex.

One at Wallasea Island last month, a couple at Terling during May at my WCBS square, and a single Small Tortoiseshell at the Naze in April. Wow

That means there have been no sightings at such prime butterflying sites as Hatfield Forest, Great Holland Pits, Friday Woods & Cherry Tree Lane, Hockley Woods & Pound/Hadleigh Great Woods, all along the coast apart from The Naze, and perhaps most surprising the whole of Langdon Hills Country Park



I might have to add the Small Tortoiseshell to my list of target species threatened with local extinction within South & North Essex

Grizzled Skipper
Brown Hairstreak
Heath Fritillary
Wall Brown
Purple Emperor - White Admiral - Silver-washed Fritillary
Small Tortoiseshell

First sighting of the year 18/03/2024:

Small Tortoiseshell
Baddow Meads 18/03/2024

And during the peak time from 25/03-17/04/2024:

Small Tortoiseshell
Baddow Meads 08/04/2024

Small Tortoiseshell
The Naze 12/04/2024

The beautiful Small Tortoiseshell

I would be interested to hear about your own experiences of an encounter with the lovely Small Tortoiseshell during 2024 - so please add your own posts below, and feel free to add some of your amazing photographs. Thank you in advance.

[essexbutterflyer]

Hi David,

This is a very interesting post, thanks for posting your data. I’ve seen a total of zero small tortoiseshells in Essex this year, but just over the border in Hornchurch (London) there were two in the spring. At the rate things are going I may have to pay your area a visit next year just to see them! Not aware of any closer locales where they are commonly spotted.

Zayed

[David Lazarus]

I’ve seen a total of zero small tortoiseshells in Essex this year, but just over the border in Hornchurch (London) there were two in the spring. At the rate things are going I may have to pay your area a visit next year just to see them! Not aware of any closer locales where they are commonly spotted.

OMG Zayed- the situation in Essex is even worse than I thought.

For data analysis, Hornchurch is regarded as being in the Vice-County of South Essex even though it is outside the boundary of Essex and is in fact part of Greater London. However, just like North Kent that incorporates parts of south-east London, South Essex incorporates parts of east London. Our branch data is actually Essex and East London - so your sightings would be included in our branch records.

To put my findings into perspective, below are the distribution maps for all sighting records for the Small Tortoiseshell during 2024. These are the 113 sighting records [not numbers] within our branch boundaries on the Butterflies for the New Millenium data bank only for ease of presentation:

Small Tortoiseshell 2024 Essex sightings
Distribution map source: Butterflies for the New Millenium

And we could look into South Essex where you live:

Small Tortoiseshell 2024 South Essex sightings
Distribution map source: Butterflies for the New Millenium

And in more detail to where you had your sightings in Hornchurch:

Small Tortoiseshell 2024 East London/S. Essex sightings
Distribution map source: Butterflies for the New Millenium

The data for sightings of Small Tortoiseshell in Essex paints a dire situation. Clearly there are greater numbers than the data shows due to many reasons. Not least the sample size of butterfly recorders is very small and obviously they do not cover everywhere. And where they do go, generally places where they expect to find butterflies to see - they record sightings. It can only give a trend by comparison to previous years. Data has its limitations - it can support a gut-feeling that something is amiss, in this case with the beautiful Small Tortoiseshell.

[essexbuzzard]

For the record, I’ve only had around half a dozen adults in Harlow this year, and no caterpillar batches. This has happened before, only to bounce back a couple of years later. But there’s no getting away from it, despite the odd good year, the overall trend is down.

[essexbutterflyer]

I’ve seen a total of zero small tortoiseshells in Essex this year, but just over the border in Hornchurch (London) there were two in the spring. At the rate things are going I may have to pay your area a visit next year just to see them! Not aware of any closer locales where they are commonly spotted.

OMG Zayed- the situation in Essex is even worse than I thought.

For data analysis, Hornchurch is regarded as being in the Vice-County of South Essex even though it is outside the boundary of Essex and is in fact part of Greater London. However, just like North Kent that incorporates parts of south-east London, South Essex incorporates parts of east London. Our branch data is actually Essex and East London - so your sightings would be included in our branch records.

To put my findings into perspective, below are the distribution maps for all sighting records for the Small Tortoiseshell during 2024. These are the 113 sighting records [not numbers] within our branch boundaries on the Butterflies for the New Millenium data bank only for ease of presentation:

2024 Small Tortoiseshell Essex.png

And we could look into South Essex where you live:

2024 Small Tortoiseshell South Essex.png

And in more detail to where you had your sightings in Hornchurch:

2024 Small Tortoiseshell East.png

The data for sightings of Small Tortoiseshell in Essex paints a dire situation. Clearly there are greater numbers than the data shows due to many reasons. Not least the sample size of butterfly recorders is very small and obviously they do not cover everywhere. And where they do go, generally places where they expect to find butterflies to see - they record sightings. It can only give a trend by comparison to previous years. Data has its limitations - it can support a gut-feeling that something is amiss, in this case with the beautiful Small Tortoiseshell.

A very comprehensive look at the small tortoiseshell in Essex David. Thanks very much! And yes, it seems the overall trend is a negative one. Grateful for the positive bits here and there however.

[David Lazarus]

Postscript Sadly, the Small Tortoiseshell I saw on the 21st of September was my final one of the year.

[David Lazarus]

Current 2024 UKBMS live data for Small Tortoiseshell from today's UKBMS Newsletter.

2024 live data for Small Tortoiseshell UK abundance
Source: UKBMS

These plots are provided as a rough indication of how the season went for [one of three] species. They show a comparison between provisional 2024 data (orange), last year (blue) and the last decade (green). They are based on the number of butterflies seen per 100 transect walks for each week of the season.
Source: UKBMS

[David M]

Thanks for posting this, David. Makes grim reading though.

The statistics reflect my own experience with this species lately, with numbers hugely down since 2022.

There are three obvious trends:

*The abnormally dry summer and early autumn of 2022 impacted nettle growth and would have limited larval progress.

*March and April 2023 were atrocious from a weather perspective; wet and cool, allowing little flight time for this early spring species to find mates and oviposit.

*The same months in 2024 were almost as bad with similar consequences.

I tend to see the bulk of my local Small Tortoiseshells through March into mid-April with another surge in numbers during the latter part of summer.

This year I saw just two during spring and my total for the year is a mere two dozen.

I hope next March is drier, warmer and sunnier than the last two. If that is the case, then I would expect to see far more than during that same period in 2023 and 2024.

[David Lazarus]

I think you have rightly described the climatic factors and how local weather conditions have made significant contributions to the reduction in numbers.

Without having any scientific data to support what I am going to say, I would have thought that there were some unseen factors that made this year in particular a really difficult year for Small Tortoiseshell. Perhaps a significant pest or combination of pests and diseases may have impacted a particular life stage, for instance.

I can only say that climate change, poor weather, severe weather episodes, as well as habitat loss and other human activities alone cannot explain the reduction in numbers here in the River Chelmer floodplain. There are large patches of lush nettles throughout Baddow Meads and along both sides of the River Chelmer. I would expect the larval stages to flourish within these habitats - unless there was an “unseen” pest/predator/disease that prevented them from becoming adults. Nectar sources too are not the problem although there could be more if managed properly.

I can’t see how Peacock numbers were not affected when for the most part they share habitat requirements and climatic conditions/microclimatic factors. Somehow the Peacock managed to cope despite the poor weather but the Small Tortoiseshell numbers are so low - wow, it will be interesting to see if they can bounce back from this.

I am honestly still upset by it and am passionate about finding the reasons why and what can be done to help them.

[essexbutterflyer]

I am honestly still upset by it and am passionate about finding the reasons why and what can be done to help them.

Same here David. I'm not sure if any large scale research is ongoing or has happened.It seems most research is from years ago where Sturmia bella was being hypothesised or very limited if recent. I wonder why there appears to be no recent extensive attempt at studying the declines.

Zayed

[David Lazarus]

Same here David. I'm not sure if any large scale research is ongoing or has happened.It seems most research is from years ago where Sturmia bella was being hypothesised or very limited if recent. I wonder why there appears to be no recent extensive attempt at studying the declines.

Unfortunately, I suspect that there is no money in conservation and I doubt that is any different for long-term research of the Small Tortoiseshell. I know of ecologists in my previous sector of Landscape Architecture who earn £30-40,000 preparing ecological impact assessments for the planning process. I was never convinced they were the type of people who were going to dedicate their lives to conservation. Hopefully there are young ecologists out there who will be passionate in taking butterfly conservation to the next level before it is too late.

I wish I was in my 20s as the person I am now