The Birds, The Bees and The Butterflies

Yesterday I was very lucky to be able to spend a full day at Knepp Estate in Sussex, one of my most favourite sites to visit. We arrived early, at 6am, for some bird ringing to start off the day.

Yesterday we were using a new bird ringing site on the estate, after success at the A Focus on Nature event recently when several Lesser Whitethroats were caught, a bird I have only ringed once before. None were seen let alone caught yesterday, which is very odd. Perhaps they have started to migrate already, however it is still quite early for the Sylvia warblers to be on the move. Maybe they just moved to a new part of the estate.

We did catch many other warblers, however, the bulk of which were Chiffchaffs with 12 caught. One Chiffchaff showed very unusual moult: most of its coverts had just come out of pin. The pin of a feather is where the feather develops before coming out of pin and growing into a full feather. What makes the moult of this Chiffchaff strange is that usually moult is more gradual than the moult this Chiffchaff has shown:

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The highlight of my ringing morning was catching my first Sedge Warbler. This was a very peculiar catch! That is because although there are a number of waterbodies at Knepp, no Sedge Warblers breed here. This individual was a juvenile, which explains it. At this time of year, juveniles are dispersing, leaving the sites where they hatched and grew up. Soon we might even be able to catch adults as they stream south to winter in Africa.

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Soon after the ringing we had to leave to a different area of the estate for a bee field trip which I was very excited about. It was organised by the Amateur Entomologists’ Society (AES). I attended a similar one at Knepp last year which focused on grasshoppers and crickets.

When the field trip got going we were surprised at small numbers of bees that we were finding. Knepp Estate is a great habitat for bees with many different flowers which cater for the different tongue-lengths of bees. For instance, long-tongued bees such as the Garden Bumblebee (Bombus hortorum) are able to feed on Foxgloves and similar plants whereas short-tongued bees like the smaller solitary bees can only feed on flat flowers such as mayweeds and daisies. There are also lots of great nesting habitats for bees, such as fence posts, old lightning-stricken trees and farmyard walls. So why were the bee numbers so low?

The two most likely reasons are due to the weather. On the day it was very cloudy and dull, poor weather for bees to be out and about as they need to warm up in the sun before they can fly. Also, it has been a very poor season as a whole for them. June was a very wet and cold month, severely hindering the opportunities where bees could go out and collect pollen and nectar.

Despite the lack of bees, invertebrates of many other orders were well-represented and we spent time recording and marvelling at those as well between looking for and at bees. One thing that we all noticed were the incredible abundance of Cinnabar moth caterpillars. Their foodplant is Ragwort, and there are thousands and thousands of them at Knepp. In fact, it is the most abundant plant by quite a long way and most plants seemed to have several caterpillars devouring their foliage. Many plants were completely devoured apart from their stem and we found instances where a group of caterpillars had munched their way through one ragwort plant and had moved to another.

When it became particularly cloudy and there were no bees in sight, I became especially interested in finding grasshoppers following the field trip last year. Ralph Hobbs led the event last year and was here again this year and together we found quite a few. We noticed that on the inside side of the ‘thigh’ of the back leg of the Lesser Marsh Grasshoppers we caught there was a dark mark that we also found on Field Grasshoppers. Meadow Grasshoppers are the main confusion species for the Lesser Marsh Grasshopper and they seem to lack the dark mark on the leg. Ralph and I reckon that we have found a new identification feature to separate these two similar species, however more specimens will have to be caught and looked at before we can say that the dark mark is a completely reliable separation feature.

We stopped for lunch at a good site, it seemed. After I had finished my lunch I went exploring in the general area and there were lots of interesting creatures to be found. There were a large number of marsh flies (Dolipechidae) on and by a large muddy puddle, the species is easily recognised by the white tips to the smokey wings. These white tips are especially prominent in the males, which use them to display to the females. It is quite entertaining to watch, especially when a female rejects a male!

Surrounding the lunch site there were many willows (Salix sp.) and some large Oaks. This is great habitat for Purple Emperors, so we kept our eyes peeled.  I had already seen a couple a few weeks ago (blog post here) but I wouldn’t mind seeing another! Amazingly, I didn’t have to wait very long, I was kneeling down looking at a large Toad that had somehow found itself beneath a tight stone when I heard ‘Purple Emperor, just landed! Purple Emperor, just landed!’ coming from down the track. Of course I leapt up and ran towards where the exclamations were coming from. Some of attendees of the field trip were looking confused as our leader, Josh Nelson, tried to point out the magnificent butterfly to them. It was surprising how difficult such a large and impressive butterfly was to spot! The reason was because it was side on to us all, therefore we could only see a sliver of black and white against the oak leaves behind it. I must admit that it did take me a while to find it but once I did I was attempting to show others the butterfly which proved to be a very difficult task, although they all got onto it eventually. There it remained for a while before a ‘Purple Hairstreak’ (definitely not our leader Josh!), flushed it from the oak leaf it was sitting on. We were able to get our best views then however, as it fluttered over the nearby sloe bush and out of sight.

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See if you can spot the Purple Emperor!

So, when everyone was ready we decided to leave the area to see if we could find some bees, although that didn’t really go to plan. We actually only walked approximately 5 metres before we stopped again! This time we heard the calls ‘Purple Hairstreak, landed! Purple Hairstreak, landed!’. Once again, I rushed towards where a group of people were leaning over peering at something on the track. There, on the bare dirt, was a beautiful female Purple Hairstreak, with patches of stunning iridescent purple on the wings. This was easily the best view of a Purple Hairstreak I have ever had. Before I have only seen these small butterflies up at the tops of hedgerows or flying several metres above the ground. So what was this Purple Hairstreak doing on the ground, exposed and with its eyecatching wings open for all to see? It was as if it was saying ‘come eat me, I’m tasty’! Closer inspection revealed that she was indeed pregnant, and appeared to be very weak because of that. After obtaining some quick photographs we managed to get the hairstreak onto someone’s hand and Ralph poured some of his (non-alchoholic!) elderflower cordial onto his fingers. To our delight, the butterfly’s proboscis came out and it started to feed on the cordial! It soon gained energy and we placed it on part of a nearby oak tree which would catch the morning sun and where it would hopefully lay its eggs. Below are some of the photos I managed to take of this beautiful butterfly.

 

Soon we did move on, however, and now that we had our eyes in, we began to spot some more bees and other wildlife. One of the richest habitats of Knepp Estate is the grassland which is peppered with some scrub. On the sandy track through the grassland there is plenty of mayweed, a flower that is similar yet much larger than daisies. There were a few small dark bees, although however much we tried we were unable to catch any to identify them. The track was also riddled with some small circular holes, which were the nests of these small black solitary bees. Eventually, eagle-eyed Josh spotted one on the ground by its nest and swiftly potted it so that he can identify it back home.

The nests in the sandy soil gave us another idea for why there were few bees about. Perhaps the unnatural number of cows, pigs and deer on the estate were constantly trampling on these nests and destroying them. That might be one downside to the rewilding project, although it is restoring habitats to what they were like in prehistoric times, so perhaps bee numbers were this low millenia ago?

Our final stop before heading back to the car park was the outflow of mill pond. The edges of the outflow were rich in aquatic and water-associated flora such as Purple Loosestife, Yellow Loosestrife and Water-plantain. Josh told us that there was a bee that has specialised to exploit Yellow Loosestrife. Unsurprisingly it is called the Yellow Loosestrife Bee (Macropis europae) and it collects the oils from the Yellow Loosestrife flowers to water proof its nest. This allows it to nest in very wet places where other bees are unable to nest. Just as Josh was saying this, Ralph called ‘is this the bee?’. Josh potted it, had a look at it and confirmed that it was the bee! Amazing! This bee is easily identified by its distinctive black and white hind legs.

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Well, there wasn’t a huge number of bees at Knepp that day, although I really enjoyed talking to other naturalists as well as recording other wildlife that I came across. I can’t wait to visit Knepp Estate again!

Britain’s Rarest Fish

Yesterday I arrived back from a week-long trip to the Lake District, which I thoroughly enjoyed. The landscape of the Lake District, with all the fells and lakes, is absolutely stunning, but so is the wildlife. In this post I will be writing about 2 of the fish that we saw on our trip, out of the 4 new species I have so far added to my Pan-species list. I am very pleased with the addition of these new species as it raises my fish list from only 7 to 11. Despite this still meagre total, I am very proud to say that following my trip I now have the 2 rarest fish in the British Isles on my list, the Schelly and the Vendace!

Schelly

The Schelly is a very rare fish , being endemic to the United Kingdom and even Cumbria. In fact it is only found in four lakes worldwide, Red Tarn, Haweswater, Brotherswater and Ullswater, and is classified as endangered. The combined area of those lakes forms the species’ area of occupancy, which is a tiny total of 20 km². That’s equivalent to half the size of Portsmouth!

During our trip to the Lake District we visited two of the lakes where the fish lives, Haweswater and Ullswater. In Haweswater, the population has been in decline unlike the other 3 lakes where the population is stable. According to the website of the International Union for the Conservation of Nature’s Redlist, which assesses species trends etc. and assigns them a category such as endangered or vulnerable, the two main reasons for the decline of the Schelly from the reservoir is water abstraction and predation from the humble cormorant. Water abstraction is the taking of water, permanently or temporarily, from a water body. The fact that Haweswater is a reservoir means that water abstraction is often practised, and this process can harm the environment. The good news is that conservation actions are taking place to conserve the Schelly, namely reducing water abstraction in Haweswater and taking control measures on Cormorants, according to the IUCN website.

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Clouds looming over Ullswater

Vendace

Now, the Vendace is the rarest fish in Britain. As a native species, confined to only two lakes globally, both in the Lake District, and introduced to one more in Scotland. The combined area of the two lakes where it is found in the Lake District is just 9.9 square km, making its native distribution area 10 times smaller than Paris! The Vendace used to be found in two further lakes, both in Scotland, however both populations were extirpated due to eutrophication. Eutrophication is the excessive abundance of nutrients in the water of a lake which causes very dense growth of plants. Eutrophication is often due to run-off from the surrounding land.

The main threats to the population of Vendace is the Ruffe, an introduced fish which feeds on the eggs of the Vendace. However, the Ruffe has only been introduced to Lake Bassenthwaite, not Derwentwater, the other lake in which it inhabits. Luckily there aren’t any clear threats to the population in Derwentwater, and fishing of this species has been banned. The Bassenthwaite population of this species even seems to be increasing. The species was declared locally extinct in Bassenthwaite in 2008 after the last fish had been recorded in 2001, but had been rediscovered a few years ago. It is possible that the fish found in Bassenthwaite come from the Derwentwater population and had travelled down the river from Derwentwater to Bassenthwaite.

The introduced population in Scotland, in Loch Skene, is doing very well, with a larger population than Derwentwater. The precise figure is nearly 10 times more Vendace per hectare than in Derwentwater, which is excellent! The species was introduced to Loch Skene when the population in Bassenthwaite Lake was seen to be very unstable due to the severe decrease in the habitat quality in the lake. This is a very good example of a successful conservation action.

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Looking across Derwentwater

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The gravel shores where I saw the young Vendace

I’m very pleased to have had the privilege to have seen these two fish as they are both in danger of extinction. Before I visited the lakes where these two fish are found I had no idea either of them even existed. Rare species like this are usually extremely poorly known by the general public and they don’t get the publicity that they deserve as they aren’t all that impressive, like tigers or pandas. However, just because they aren’t impressive it doesn’t mean that they don’t deserve to be saved from extinction. I think we should raise more awareness for these not very well known species in order to conserve them for future generations to cherish and enjoy.

The Emperor of Knepp

My Pan-species List is going along quite nicely and I think I will comfortably reach 2000 species by the end of the summer holidays, which is my target. However, I haven’t added another new butterfly species for a very long time. So on Tuesday, that is what I set out to do.

Knepp Estate near West Grinstead is one of the best places in Sussex to see the elusive Purple Emperor butterfly. Purple Emperors spend most of their time in the canopy of large Oak trees and there are many huge trees at Knepp, which also makes the estate good for saproxylic beetles. Saproxylic beetles are beetles that depend on dead or dying wood. Also, due to Knepp being part of a rewilding project, there is lots of dung about. Rewilding is where you take a location and try to restore it to the state that it was in many centuries ago. This involves using substitutes for wild boar (Tamworth pigs), aurochs (long-horn cattle) and other animals. Dung is good for Purple Emperor butterflies because they can harvest moisture and nutrition from it.

Apparently, to entice Purple Emperor butterflies down from the canopy, you need a banana and some fish paste. On Tuesday we chose fish paste, and we spread some on a slice of bread. After we had walked down a nice track to get to the Purple Emperor hotspot in the centre of the estate, we climbed up onto a tree platform and I unwrapped my fish paste bread. It wasn’t long before the flies began to arrive, but Purple Emperors were no where to be seen.

The weather conditions were far from ideal for the Purple Emperors. It was dull and very windy, there was no sun to warm them up and at the tops of the trees even these very large butterflies would have difficulty flying. However, we kept searching, walking along rides where we hoped the butterflies would show. We were just about to head home when the sun miraculously came out from behind the clouds. It immediately warmed up but we didn’t think it would last for long. We carried on walking down the ride when I nearly stepped on a long black thing. To my surprise it exploded from the ground just beneath my looming foot and flew towards the hedge on the side of the ride. I had nearly stood on a Purple Emperor! I hadn’t noticed it because its wings were closed making it look like a black twig from above. It wasn’t the best of views, but I had seen a Purple Emperor!

Sooner than I thought, it came back and landed on the track, where it probed the ground with its proboscis. It was picking up minerals from the dirt that it wouldn’t be able to get in the oak canopy. As it spends most of its time in the trees, it doesn’t feed on flowers which is very interesting. Instead, it most commonly feeds on the honeydew that is excreted by aphids and also sometimes on sap. Another interesting point about the Purple Emperor is that they are sexually dimorphic, which means that the males are different to the females. The males are much more beautiful and have a brilliant purple sheen when the wings are at a certain angle to the sun. However, the female is larger, dull brown and never has the purple sheen of the male.

While the butterfly on the ground was picking up minerals, I spotted a second butterfly flying around at head height. However, it was too wary to come down and retreated back to the canopy. The male on the ground was also flighty, but I did manage to get a few photos from a distance:

So, that is my 33rd butterfly species. Which butterfly will be next on my list?

Golden Robber

Diptera, the true flies, are not one of the most glamorous groups I must admit. However, they are one of my favourites because of the sheer diversity of shapes, sizes and colours. I recently added my 100th fly species to my Pan-species List, a figure I have been working towards for quite a while now. The fly species that I am writing about today was my 103rd.

Yesterday I went on another Hedgecourt Invertebrate Survey trip to try to add more species to my list. There was lots about and only about 10 metres into the reserve I was distracted by the many invertebrates I was recording. These included a White-legged Damselfly and a snipefly (Rhagio tringarius) that voluntarily flew into my net. I was so distracted that at first I didn’t notice a medium sized black fly that had landed on my hand. Annoyingly it was on my right hand, my camera hand, so I found it difficult to take a photo. Then I realised that it was strangely placid, and I coaxed it onto my left hand where I was able to photograph it.

The fly had its wings folded back, which made it look like a Bibio. However, when I blew the wings apart and off from the abdomen it clearly wasn’t a Bibio. It had a long abdomen with a ring of golden hairs between each tergite (segment). To identify it I posted the photo on the identification forum on the Dipterists Forum website. The Dipterists Forum is a society set up for the study of flies. The Dipterists Forum run regular field meetings, such as the current one in Canterbury, curate Diptera-related Wiki pages and a whole host of online forums and run recording schemes for different fly groups. I received an identification for my fly very quickly: it was the Golden-haired Robberfly.

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Before I saw this one, I hadn’t seen a robberfly for a surprisingly long time although they are very interesting insects. They belong to the family Asilidae, with about 5000 species worldwide. The alternative name ‘assassin fly’ is very appropriate as they are very effective hunters that tackle difficult prey like wasps and occasionally even dragonflies. They are very fast flying, allowing them to outpace most of their prey. They are also patient, sitting on a sunny plant or log waiting for suitable prey to fly past. Even robberfly larvae are formidable predators, feeding on other insect larvae and eggs beneath the soil.

This robberfly wasn’t the only interesting invertebrate I found on my survey trip. I also found two caterpillars that I have been wanting to see for a long time: Mullein Moth caterpillars. They are very impressive and, as the name suggests, they usually feed on Mullein. However, some other plants are sometimes also fed on. I found mine in a habitat I really wouldn’t expect to see them in. I have never seen Mullein growing in Hedgecourt at all… let alone a wet reedbed! Still, there they were, a pair of them. They were large, well grown, and stunningly coloured.

If they weren’t feeding on Mullein, then what were they feeding on? Water Figwort has been recorded at Hedgecourt, and is apparently a known foodplant. Unfortunately at the time I didn’t note down what they were feeding on but I will look to see if there is any Water Figwort where the caterpillars were feeding the next time I visit.

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