The latest report from Michael Walter:
There’s no getting way from the fact that the main talking point this summer has been the weather. In the 13½ months since the start of July 2021 rainfall has been above average in only two months, and total rainfall during that period was just 65% of the expected. Add to the mix an immobile heat dome and you have all the ingredients for a perfect fry-up, culminating in a roasting 40.2°C (according to my thermometer) on 19th July. On that day most people who had the option stayed at home, or at least in the shade, but I had scientific observations to make in the wood, and pedalled off into the oven. What struck me immediately was the deathly hush (no birdsong), wilting vegetation (even the hardy willowherb), and an almost total absence of most butterflies. The top graph shows how poorly butterflies have been performing this year, and in July the numbers simply crashed. Note, however, that I mentioned above “an almost total absence of most butterflies”, as there was an interesting exception, with hundreds of purple hairstreaks, which normally congregate around the top of the oak canopy, descending literally to ground level in shady areas, where the temperature may have been 10-15° lower. I have only observed this phenomenon so strikingly once before, and that was way back in 1983, when the summers certainly weren’t as hot as now. I don’t have any bird figures for this period in the wood, but I carry out a weekly 30-minute count in my garden, and the second graph shows that numbers in the previous three months were fairly consistently in the teens, but dropping to just four on 19th July, when the birds presumably lurked in the shade, moving as little as possible. Interestingly, the number shot up to 41 two days later, way above normal, when the temperature was 15° lower, leaving me to wonder if that was just coincidence or some sort of reaction to the previous heat.
By definition red-letter days are rare, and it seemed a long time since I had recorded something really exciting, but on 29th July, while carrying out a routine butterfly transect, I saw a fritillary flying close to the ground. Too small to be a silver-washed, and quite unlike the flight of a heath fritillary but, as soon as it landed and closed its wings to reveal a bold pattern of large silvery ovoids, I realised that this was the very rare Queen of Spain fritillary. Primarily a butterfly of southern Europe and north Africa, it is a species of dry, open habitats, so seemed rather out of place in the wood. With no more than 400 UK records in the past 300 years, this is a decidedly rare vagrant.
Michael Walter
Queen of Spain fritillary in Blean Woods on 29th July. Photo courtesy of Rob Dixon, RSPB assistant warden.