Report on the 2020 Butterfly Transect season

March arrived and the butterfly transect team of Grahams Harris and Kenward and I (Brian Gardner) started the count-down to April’s start of the 2020 butterfly counting season only to have our plans cancelled by the Covid 19 lockdown. A few weeks later the lockdown restrictions eased, allowing us to walk our first socially distanced transect in brilliant sunshine on the 19th May (week 7 of the 26 week Transect calendar). We were rewarded with seeing 42 Dingy Skippers and 21 Brimstones – a nice start for us. 

After that flying start the following counts were steadier until mid-June’s sudden explosion in the numbers of Meadow Browns, Marbled Whites and Small/Essex Skippers, and we were grateful for having our new team member, Roger Vye, to help with the spotting and counting. That busy day proved to be the high-water mark in the season’s count – 517 butterflies from 12 species. 

In week 16 (mid-July) we recorded our highest ever number count of 22 species, including our only 2020 sighting of a Small Blue. Like the one below, this was on our Hither Field Kidney Vetch patch but others were seen elsewhere on our ‘manor.’

Female Small Blue, Hither Field: Graham Kenward

With August came the summer’s heatwave and transects 18, 19 and 20 were walked in temperatures above 30 degrees. In similar heat last year we saw exceptionally high numbers of Meadow Browns, Marbled Whites and Small Heaths but that didn’t happen this year: numbers were down – perhaps the butterflies’ food plants were adversely affected by 2020’s long dry spring. 

From mid-August onwards the weekly counts declined steadily towards the season’s end but at a similar rate to our observations over previous transect seasons.  However, in the final few weeks, among the species hanging on into the less predictable September weather, we enjoyed seeing a pair of Brown Hairstreaks and a Clouded Yellow.
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This year’s total count was 3,547 across 31 species. As for previous years, I have completed a spreadsheet for 2020’s transects, available here. 

The grand total of sightings for each year is affected by the number of transects walked, by unfavourable weather and the availability of transect walkers. For a better representation of the annual figures, I’ve divided each year’s grand total by the number of transects walked, to show the average number of butterflies counted on each transect, as shown in the table below.

Report by Brian Gardner