This year has not been a particularly good year for butterflies, with the cool and damp spring affecting most species. Locally, the Silver-spotted Skipper and Dark Green Fritillaries have been the species that have been affected the most, but Adonis Blue have also been well under par.
The species that I study the most, the Wall Brown, has done a little better, although even these have not been as numerous as most years. I have been hoping that the 3rd brood would do a little bit better, as the larval food plant is grass, and with there being no shortage of that this year, the butterflies should flourish. Certainly, as the 3rd brood started the numbers of Wall Brown in their traditional 3rd brood sites were looking promising, but numbers elsewhere were not so good, however, in the past week numbers have grown, and despite poor butterfly watching weather, I have seen well into double figures of the species several times now. I have also witnessed several butterflies egg laying, which is very encouraging.
On one walk locally, after already seeing a mating pair of Wall Brown, I saw a female Wall Brown fly out of a culvert that had been dug a couple of years ago to take away flood water from a footpath. This had left a scrape where sparse grasses grows and the roots are exposed. This is ideal for the Wall Brown as the female often lays her eggs on the exposed roots of grasses. I guessed when I saw her fly off that she was on an egg laying mission, and as soon as I looked through the close focussing binoculars I saw a Wall Brown egg. On closer inspection I saw another one.
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Mating Wall Brown.
After finding the eggs, I have walked past the same spot twice more this week, and each time I have added more eggs to the count. In that same spot I have now found 9 Wall Brown eggs, which is by far the most I have seen in one spot. I also found 2 more in other locations.
The culvert where the eggs are.
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Two Wall Brown eggs.
Surprisingly, I have also this week seen 3 aged Adonis Blue. Maybe they didn't have such a bad year after all and many emerged between my visits?
Another species that I now study is the Lace Border. A rare moth that now breeds locally, and I suspect has a 3rd brood, despite all the books saying it only has 2 broods. Each year I have seen evidence that my sites have 3rd broods, perhaps due to the 2 sites having been started by continental migration? After the 2nd brood fizzled out towards the middle of August, there was for the 3rd year running a sudden increase in numbers in late August to mid September, with 20 seen on one count at the beginning of last week.
Lace Border.
THe high summer butterflies seemed to do ok, those which wintered as imagos have had a terrible year
ReplyDeleteInteresting. Do you get much in the way of frosts there? I believe that Wall Browns over-winter as late stage caterpillars and the season length is critical to the species survival. They have been moving up the country and arrived on the coast of SE Scotland in the early 2000s. They only reached here (further inland) last year. I have been watching records of them getting closer, but saw one last year and again, one here this year on the 17th September!
ReplyDeleteIt has certainly been a poor year here for butterflies. A few species, such as Orange Tips and Ringlets have done well, but everything else appears to have been much lower in numbers. I am still waiting to receive all of the records from local volunteers to get a better idea of what has been going on.
Hi Nick.
ReplyDelete3rd brood Wall do well down here, but only in areas where it gets autumn warm days, so you will almost certainly only get the 2 broods in Scotland. Being near the coast here stops it getting too cold during the winter, so there isn't a problem with them making it through to the spring. I study and monitor the larvae over winter and see them feeding even on frosty days, once the sun has warmed the area up enough.