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:
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.
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.
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.
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!