Finally, able to venture out post-holiday isolation, yesterday I completed the last butterfly transects of 2020. 

The Butterfly monitoring programme runs weekly from Apr 1st to Sep 29th every year, which is 26 weeks of monitoring.  

Usually the last couple of weeks are fairly tiresome as we’ve seen everything come and go, and there are just a few worn out tatty stragglers left, if anything at all. Some years, the last week is too cold, windy or cloudy to even be within the defined conditions required to undertake the survey, and it was looking a bit that way this week, but fortunately the wind dropped and the sun came out yesterday, so I did the two surveys (Barton and Westfield).  

How we monitor butterflies

I had offered to do the final week after having had to rely on the volunteers for the last month or so while I holidayed and quarantined, I basically fancied having the excuse to have a walk round the farm after being shut indoors for a fortnight, and was not expecting much of interest. 

How wrong I was! 

Brown Argus Butterfly
Brown Argus Butterfly
Barton had common blue, 2 small copper and a speckled wood among the small selection on offer, while Westfield had a brown argus and 3 small coppers as well as a speckled wood. 

But the biggest surprise was the very last butterfly of the 2020 transect season, a fresh-looking meadow brown which must have just emerged this week. These butterflies are normally seen in mid-June through to the end of August/early September, and when they are 
out, they are the most common species in our meadows.  

Meadow Brown Butterfly
A few are recorded nationally in later weeks, even into October, most years, but we’ve only had two records of one in this final week before (
in 2011 & 2015). No-one is quite sure if these late individuals developed from eggs laid early in the same year, and had rapid development, or if they are individuals that were laid as late eggs in 2019 and have taken a longer time to develop. 

The other 4 species are all certain to be 3rd broods – this is normal for speckled woods (which start early in the year and just keep breeding) and is common for small copper. However, it is less usual for common blue and brown argus. It shows the flexibility of their breeding behaviour. Further north, common blues only have one brood per year, whereas in our area they usually have two, and further south in Europe three is common. 

I also recorded 1 peacock, 1 red admiral and 4 small white butterflies, all of which are normal at this time of year. 

Dr Vince Lea
Head of Wildlife Monitoring

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