A year with a record breaking early spring followed by a wet windy summer made for a mixed year


The season was rather dominated by the pandemic and we were unable to record for the first 6 weeks of the 26 week recording season but a majority of recorders managed to restart in May or June and then put in their normal number of walks. We appreciate the charities suffered and staff were furloughed and unable to undertake their duties and some of us were shielding. We hope they will be back in 2021 as the last lockdown comes to an end but preparations are behind and may make it difficult to repair some of the losses in 2021 .

The Weather

After a very wet and warm autumn in 2019 with floods which returned in late February to be promptly followed by lockdown 3rd week of March! At which point the sky cleared to weeks of glorious sunshine and record breaking temperatures and more importantly a very dry spell which is becoming a feature of recent spring weather. Few can remember such an early and protracted spell of fine weather through April and then into a heat wave in May. As a consequence many species emerged very early and we were not there to see them. Some were already in decline or had finished before our first recording day in mid May as the lockdown rules were eased and transect walking was allowed once again. By this time the heatwave had really set in, the ground dried and cracked and dryer grasslands suffered badly with plants stunted and withering lower leaves. Some plants were only half their normal height and size. The spring and early summer species were emerging nearly 10-14 day early with 23 species in the UK recording their earliest ever emergence: an exceptional year. Hopes were high that unlike 1976 the heat waves of 2019 would not be followed by a disastrous decrease in numbers of 1977. It has not repeated; and most species came through although there were more losses than gains. The weather broke in the first days of June and went in reverse with a cool June and a conveyor belt of Atlantic storms which pock-marked the rest of summer particularly a stripe across the midlands into Yorkshire. The summer in many ways was a disappointment after 2018 and 2019 but there were good spells between the storms. Finding good days with sun and temperature were often hard even in high summer. The end of the season was average

The Results

A summary of all sites was prepared in spreadsheet form below. For each site the percentage change from the 5 year average is shown for each species. The number of negatives and positives are then totalled and the the first conclusion was many more species were negative (14 ) that positive (9) with 3 uncertain. Included is also the national trends of 2020 compared 2019 and compared to a much longer 10 year average. 2020 follows on as a good year with a pattern now of three good years although 2020 is somewhat down on 2019

As ever there is a good deal of variation you might expect for a biological organism but still we can draw a few trends and use them when interpreting each transect later.

The golden skippers were both down a lot which could be weather related as they prefer longer grasses which had their growth stunted in spring 2020 particularly on dryer limestone sites of the tabular hills like Pexton Bank . In contrast after the winter flooding on some sites in winter you can pick out some increases on wet sites.

Large and Small Whites were up a little maybe with the good spring and a second generation but there was considerable variation between sites. In contrast more moisture loving Green-veined White was somewhat down particularly on the dryer limestone sites. Due to the necessity to estimate during lockdown 1 we cannot be certain about Orange tip or Green Hairstreaks.

Small Copper shows no pattern and although strong differences as does Brown Argus and Common Blue a slight decrease but with a good deal of variation. Holy Blue is a little uncertain due to the small sample size.

The Vanessids were interesting with the migrant Painted Lady nearly absent and Red Admiral well down along with Comma. Peacock also showed a slight decrease but the highlight of the year was all sites had many more Small Tortoiseshells which had a boom year on many sites. This was particularly pronounced in the north of England

Dark Green Fritillary had a good year while Silver-washed on one of its main sites Bishop Wood was average, but sample size makes thes conclusions uncertain

Possibility for the same reasons the drought probably played a part in the Skippers and Green-veined White being down Speckled Wood suffered bad losses in 13 out 17 sites and Wall Brown suffered equally badly

The Browns in general were a mixed bag with the damp grassland loving species not fairing so well with Ringlet down in 11 of 18 sites and Gatekeeper down in 6 out of 8.

In contrast Meadow Brown emerged well with increases in 11 out of 18 while the fine grass loving Small Heath had a very good year only down on the thin limestone soil at Hawnby. This could be they finished their development earlier than the later species and were therefore less effected by drought

National Comparison

When compared to the national picture there is quite good agreement with this analysis of selection of Yorkshire UKBMS transects below . Both Large and Small skippers being down and Dingy up while Small and Large White were also up .

It is tricky with the spring flying species as we have so few accurate numbers for Orange Tip or Green Hairstreak however there is a close match with the increase in Brimstone numbers. Common Blue was down as was Red Admiral and Painted Lady teh later by 99% which matches the rest of The UK . There is very good agreement that Small Tortoiseshell seeing a 130% increase. In yorkshire the Peacock were down while nationally they were up. Comma was down in Yorkshire as well as nationally. Dark Green Fritillary we are in agreement with national and they had a good year. We agree that both Gatekeeper and Ringlet were down nationally and in yorkshire but in Yorkshire Meadow Brown and Small Heath was up .

Transect reports 2020