Collard Hill Large Butterfly Blog – 21 – 26 June 2020

Over the last 5 weeks we’ve watched a lot change on Collard Hill.  The Large Blues began emerging on 29 May. We’ve watched the types of vegetation shifting as days became longer and the weather moved through extreme dry to extreme wind and rain at times.  

We noticed how the Large Blues would spend restless mornings some days, hardly ever settling on plants, constantly on the wing, circling around their preferred areas of the hill.  I have managed to take photos of the very few Large Blues that have eventually settled to feed or to lay an egg but in general, the past week has been deliciously frustrating because our favourite little creatures have been so hard to keep up with!  Often, we’ve just confirmed our identifications with binoculars and moved on, knowing that they wouldn’t be settling for us to get a better look at them.  That has meant I’ve been able to train my camera on some other amazing plants and animals too this week which I’ll come to a little later in the blog.

There certainly haven’t been so many Large Blues to see in recent days.  Our counts have been lower since mid-June and fewer than 10 were spotted each day across the whole hill since the 13 June.  The peak counts of 28 were both around the start of the second week of June.

Because the weather has often been colder and they have still been so active, we have often wondered how they managed to burn so much energy staying on the wing for so long while rarely stopping to feed on energy-rich nectar.  The drive to find a mate, fertilise and lay eggs on good quality thyme buds must be overwhelming and looking at the appearance of some of the adult butterflies, many with those beautiful blue wing scales worn and faded, that effort is obviously a real individual sacrifice. 

Above is a picture I took of a Large Blue butterfly laying an egg on Weds 24th June.  This is 23 days after I first observed them egg-laying on Collard Hill this summer, so the breeding season has been of a good length. We’re hopeful that a good number of eggs will hatch Collard Hill’s 21^st generation of Large Blues successfully in the next chapter of their recovery story.  Susie and I are glad to have been able to help the Collard Hill team monitor the population while the site has been affected by lockdown restrictions.  Watching their tireless efforts and occasional battles with the elements has been a positive experience for us too.

Late on Friday 26 June I went up to the hill in the evening light and saw something special.  A red ant worker almost certainly Myrmica sabuleti was foraging amongst a patch of wild thyme flowers.  

This is the type of activity that the Large Blue caterpillars will exploit and it’s likely that very soon, several caterpillars will be reaching the stage in their development where they deliberately drop from the thyme and begin to emit a hormone very much like the hormone the Myrmica ant’s own queen emits.  Cleverly the caterpillar will convince the ant that it is one of its own colony’s grubs and that ant will pick it up and carry it down to the relative warmth and safety of the ant’s underground colony to tend to it as it would one of its own grubs.  It is thought that it takes the entire annual production of a nest of about 350 workers to rear just one caterpillar so that ability of Collard Hill to support these Myrmica ants is vital and is the main reason that the grazing on the site needs to happen right up until mid-May, keeping the grass short and helping the ant nests warm up in direct rays of the sun to the optimal temperature for those ants to thrive.  This is such an amazing co-dependence and a type of ecology that shows just how much each species in this community can rely entirely on the successes of the other species that they share the hill with. 

On that subject I’d like to showcase the rest of the wildlife we’ve seen across the hill in the past week.  The rains in mid-June really brought about a change in vegetation and many anthills interestingly have mixtures of plants crowning them, from lady’s bedstraw, to common and spiny restharrow, to Bird’s-foot trefoil and of course, wild thyme.

Patches of bramble and gorse on the lower slopes have flowered, and grasses have developed seed heads.  The plants flourishing like this has had a knock-on effect and the diversity of invertebrates we’ve seen has really increased.  We’ve seen a great many hoverflies (including Volucella sp, Helophilus pendulus and Scaeva pyrastri pictured) and a variety of honeybees and bumble bees (which I hope to detail more in further blogs) busily visiting flowers.

Many moths have been emerging and while scanning the scrub plants for Large Blues we spotted several Geometrid moth species like the Yellow Shell as well as this Beautiful Hooktip moth, which is a relatively scarce UK moth.  What a great name! 

This Mint Moth was a really nice discovery too, also enjoying the many flushed bramble flowers out now.

Another very interesting find for me was this Scorpion Fly, Panorpa Germanica

This male Scorpion fly’s large tail appendage is just visible in my photo here.  Also found at the same time in the lower slope nettle patches was a very boldly coloured male Banded Demoiselle, Calopteryx splendens. 

What a fine specimen and I think he knows it looking at his pose!

This Large Blue is sharing a gorse bush with what appears to be a late-instar nymph of the Gorse Shieldbug, (Piezodorus lituratus I believe, although I’m ready to be corrected here as I am new to identifying shield bug species!).

Interestingly, seeing our Large Blues alongside the armoured exoskeleton this young shield bug is busy growing, I was reminded of how the invertebrate world can be a tough and threatening place.  Although the caterpillar stage of the Large Blue, with its cannibalistic and carnivorous habits can seem a bit gruesome to us, it’s worth remembering that the soft and vulnerable nature of many caterpillars often leaves them cast in the role of “juicy foodstuff of choice” for so many other animal species across the world.  A recent study of a Mongolian Cuckoo in fact showed it had made an astonishing 26,000-mile journey to South Africa (one of the longest migrations of any known animal) across 16 countries fuelled almost entirely on caterpillars!  Perhaps it’s only fair then that a few caterpillar species do take a stand and become “the eaters” as opposed to “the eaten”! 

In last week’s blog we referred to a relatively rare Odonata (dragonfly) species, the Scarce Chaser and moved swiftly on in our blog to cover up the fact that I hadn’t managed to get a decent photo.  This week though I was in luck and got these two pictures of what I believe to be an immature female.

Other nature reserves in Somerset such as at WWT’s Steart reserve have begun to report this Category 3 Red Data Book species too which is encouraging as it has been known in only 6 main localities in the UK in recent times …. Also… is she smiling at us? I’m not sure.

We’ve begun to see the first Ringlet butterflies emerge in the past few days too. 

Although, appearing superficially similar to the much more common meadow brown (also pictured) when in flight, on closer inspection the Ringlet has a really gorgeous set of clear rings across its upper and lower wings. 

I’m glad we’ve been taking the time to look out for these guys emerging.  At one point I didn’t think we were going to see them as every brown we observed was turning out to be a Meadow Brown for quite some time.  Also seen after an absence of about 3 weeks was the Peacock butterfly who’s amazing wing patterns clearly deserve a feature in this week’s blog.

On a final note, the most notable bird experiences this week was watching a red kite entering Collard Hill’s airspace early one morning and swiftly being joined by a female sparrow hawk and a group of noisy herring gulls.  Red kites have definitely not been regular visitors to the area until recently.  My neighbours have quite reliably let me know that this year has been the first in many years that Red Kites have been seen over Compton Dundon and the local area.  Red Kites, like the Large Blues have been making a comeback after concerted conservation efforts in the UK. This was a sight that made me really happy, and then to spot a Common buzzard high up above the Kite and the Sparrowhawk really topped it off.  I’ve seen the Red Kite on two further occasions since and although it’s missing wing feathers help me to identify the same individual it obviously has had a tough time settling into the community. 

I know I’m not the only one happy to see such beautiful scavenging birds getting established again around the reserve as they do play a vital role in cycling nutrients back into the ecosystem and of course adding to the visitor wow factor alongside the Large Blue.

I’ll finish by showing you again just how beautiful our Large Blues, our little living pieces of summer sky have been this summer so far.  Here’s to some more fine sunny days as we move into July next week.