Tricky Zygodons! Or are they?

Last Sunday I was able to attend a field trip of the South-East branch of the British Bryological Society, to Duddleswell Valley nestled in the expanse of Ashdown Forest. The key site in this valley is a wooded ghyll, which has been a very popular location for bryologists since at least when the brilliant botanist Francis Rose visited in the mid-1950s.

Once we had waded our way through no less than eight different species of Sphagnum mosses we arrived at this famous ghyll and what greeted us was a steep and slippery slope down to the stream below us. Luckily we all made it down safely and we were able to begin!

We worked our way slowly down the ghyll, finding extreme rarities such as Campylostelium saxicola; admiring huge walls of fruiting Pellia epiphylla and finding ourselves knee-deep in shallow-looking mud. I even managed to put my foot in the middle of the largest colony of Nardia compressa in South-East England!

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A large part of the only colony of Nardia compressa in the South-East

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Nardia compressa

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Campylostelium saxicola

Near the end of our excellent and bryophyte-rich walk we came across a good stand of willow trees with many species that we hadn’t yet encountered that day. These species included a small, inconspicuous tuft of moss, a Zygodon species. There are four regularly occurring Zygodon species in the South-East and they are hard to separate in the field. To be certain of an identification to species level you really need to get out the microscope.

Therefore I took a small part of the moss back with me to work on. I was expecting it to be a tricky task that might take me a while to perfect. What surprised me was that it was quite the opposite!

The features to look at are the gemmae. The gemmae of Zygodons are single cells that detach from the moss in order to reproduce asexually, meaning that the fusion of male and female sex-cells (gametes) is not necessary. When mosses and other organisms reproduce asexually like this it is referred to as fragmentation.

Not knowing how to get the gemmae off the moss and onto the microscope slide to examine, I first tried taking a small stem of the moss and seeing if I could spot any gemmae around it. This was unsuccessful and so for my second attempt I simply tapped the clump of moss onto the slide, added a drop of water and a cover slip. I placed this slide under the microscope and I could immediately see several gemmae under 100x and 400x magnification. That was much easier than I had expected!

Next came the actual identification of the Zygodon. The very helpful Brad Scott had narrowed my moss down to two species, Z. conoideus and Z. viridissimus. He also supplied photos of the gemmae of both conoideus and viridissimus, so all I needed to do was compare the gemmae of my moss with Brad’s excellent photos. It was clear: my moss was definitely Zygodon conoideus!

This experience has certainly shown me that not everything that needs microscopic examination is difficult. Certainly some species require very fiddly work to separate but that is not always the case.

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My photo of a gemma of Zygodon conoideus

Twit.

Yesterday I found myself lying down on an edge of a crater-sized hole by the side of the River Cuckmere, with my binoculars pointing down at a tiny, drab, little brown job scurrying about amongst dead grass and plant matter. Streaked brown all over, it resembled a small mouse creeping about feeding on minuscule seeds. The only bit of colour on the whole bird was its tiny yellow bill which would open occasionally to emit its single-noted ‘twit’ call from which the bird’s name ‘Twite’ derives.

Twite are usually gregarious birds in winter, feeding among plants along the coast before returning in Spring to their breeding grounds in the moorland. They are most commonly found between October-March on the east coast of England, where British breeding birds meet continental birds in saltmarshes and other coastal habitats. They are only rarely encountered South of Suffolk nowadays despite there  having been a regular wintering population on the Swale in North Kent in the past. They are therefore real rarities in south coast counties such as Sussex and they have appeared to be declining too.

Before the 1990s, double-figure counts were annual phenomena. However between 1990 and 2000 they were only rare occurrences. Now they have declined so much in Sussex that the last record on the Sussex Ornithological Society’s sightings page prior to 2017 was of a single bird with Linnets at Pagham in November 2013.

This particular Twite was first discovered in a patch of brambles along the River Cuckmere, East Sussex on the 5th of February. I was expecting it to be only a short-staying bird and that it would disappear soon. However it was seen regularly until the 15th February. For a period of 5 days after that it was looking like it had left with no news reported on the Sussex Ornithological Society’s sightings page.

Fine weather in Sussex allowed us to visit the Seven Sisters Country Park, and I took the opportunity of making a short walk to the coast through the marshlands of the Cuckmere river delta with no prior thought of seeing the Twite.

However the route we took happened to pass the site where the bird had been frequenting. Only about 30 seconds after arriving at the crater-like hole in the riverbank where the bird had been seen previously, I noticed a tiny bird fly up to perch on a large unidentified object which could have been a large piece of Styrofoam packaging. It proceeded to drink from a hole in the odd object while I managed to get good views of the bird through my binoculars. Small size; brown, streaky appearance; yellow bill… it had to be the Twite!

After allowing me to get some photos of it in the open it flew back down into the dead plant matter and continued to feed only 5-10 metres away from me. Despite its amazingly effective camouflage I was able to watch the bird well for quite a long time. It appeared to be oblivious to my presence and wasn’t wary at all, which surprised me for such a small and vulnerable finch. It felt like a great privilege to be able to get such close views of this Sussex rarity.

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Feeding amongst the dead grass and plants

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Drinking from the unidentified object

Here you can find a short video of the Twite:

2000 and beyond!

As many of you know, I have been keeping a pan-species list for a year and a half. A pan-species list (or PSL) is a list of all species that you have seen within either the UK or Britain and Ireland. My main target, that I set in the new year, was to get to 2000 species by year-end, which was always going to be a big challenge for me. I started the year on around 1300 species and retrospectively I am very pleased at the number of species I added during the course of the year.

Just a couple of weeks ago I was on the home straight. I needed just 29 species for me to reach the magical number however I was in the last, and generally toughest month due to the lack of many invertebrates. However, I had a field trip planned which would hopefully get me all the way.

On a cold Sunday morning I met several other bryologists (bryology is the study of bryophytes – mosses and liverworts)/naturalists in a car park in the Lewes district of Sussex. We were at Chailey Commons for a meeting of the South East group of the British Bryological Society.

Our first stop on our outing was the short acidic grassland immediately next to the car park. There were a few common grassland species here, including the very familiar Rhytidiadelphus squarrosusor Springy Turf-moss. This species is not only confined to acidic grassland like this but can also be found almost anywhere with short grass. For example it out-competes the grass in our lawn in some places! Once you have seen this species regularly it becomes quite distinctive, it is medium to large sized (for a moss!) with a red stem. It has very short, thin leaves on the stem as well as slightly larger pointed leaves on the short branches and at the apex.

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Springy Turf-moss (Rhytidiadelphus squarrosus)

Another species found in this short grassland was Kindbergia praelonga, or Common Feather-moss. This is another largish moss which, as its name suggests, resembles a feather. Unlike Rhytidiadelphus squarrosus is completely green, including the stem. It has opposite branches with leaves similar in size to those on the green stem. The branches become shorter, like the tip of a feather.

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What I believe to be a frond of Kindbergia praelonga

After examining the grassland, we moved to a small patch of woodland around a quite large but seasonal pond. This pond is one of the few sites outside of the New Forest for Fairy Shrimps, however I needed to have been visiting in summer for a chance to see one of these rare crustaceans.

In this small wood we found a number of common woodland species, including our first liverworts of the outing. The first liverwort I came across was the small but abundant Metzgeria furcata, also known as the Forked Veilwort. This liverwort is very thin and forms small patches on tree trunks with the thalli (the leaves) adpressed to the substrate. It is the most common thallose liverwort and away from the coast, the most frequently encountered Metzgeria species. It also occasionally grows on rocks, although more frequently in the west of Britain where it is generally damper.

Along with that species of Metzgeria we also came across another species of the same genus: Metzgeria fruticulosa, or Bluish Veilwort. This is much less common than M. furcata, and a new species for me. This species is separated from furcata by the gemmae, which is “a small cellular body or bud that can separate to form a new organism”. Metzgeria furcata only produces gemmae rarely in Britain however fruticulosa is almost always gemmiferous, with gemmae located at the tip of the thalli.

We also encountered several patches of the moss Fissidens taxifolius (Common Pocket-moss) on the soil on the steep bank leading down to the pond. The genus Fissidens is a tricky genus for beginners as specimens often need close examination, either in the field with a hand lens or with a microscope. Luckily I was with lots of people much more knowledgeable than myself, so the specimens we found were quickly identified as this species.

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A species of Fissidens from the Cotswolds last year

After recording everything that could be found in that small patch of woodland we headed to a habitat I have never explored before: a WW1 trench! There were a number of very interesting bryophyte species in this trench that was used for training in the Great War, including one of the least common bryophytes of the meeting: Aulacomnium androgynumThe common name of this species is Drumsticks, named after the very distinctive reproductive feature, which comprises of a long stalk with a ball of gemmae at the vertex.

A variety of different mosses and liverworts were not the only new species I found in the wartime trench. There were also a range of ferns growing on the muddy bank and luckily a member of the Sussex Botanical Recording Society, Helen Proctor, was on hand to help me identify a few. Most were common species that I had recorded before, however one was a common species that I hadn’t recorded before! This was the Broad Buckler-Fern, Dryopteris dilatata. Distinguishing this species confidently from other species is possible by looking at the brown, papery scales on the stem. If these scales have a dark centre, then they belong to the Broad Buckler-Fern.

After a thorough exploration of the trenches, we moved on to an area of damp heath. Here there were Sphagnums aplenty! Sphagnums are large mosses which love damp, boggy habitats on the edges of streams and other water bodies as well as in bogs and marshes. The genus is quite easy to identify from other mosses due to its size and elongated, upright shape with a thick capitulum, which is a compact head containing new branches. However, identifying Sphagnums to species level is much trickier! For a confident identification one will need good literature, such as the key in the British Bryological Society’s Mosses and Liverworts of Britain and Ireland: a field guide. Fortunately there was also a Sphagnum expert with us who was able to verify what we found. I was quite pleased at the number of Sphagnum species we recorded on the outing: compactum, fallax, capillifolium, papillosum, palustre and fimbriatum. However, this is only a small fraction of the species of Sphagnum in the UK!

While we were examining the Sphagnum one of the members of the field outing flushed a medium-sized, stocky bird from the leaf litter. It flew high in the direction of the road. I stared at it as it flew off with my mouth agape for a fraction of a second, before I exclaimed: Woodcock! These plump wading birds are related to the Snipes, however they are unusual in that they are nocturnal; they often feed away from water (on moist pastures for example) and they roost in woodlands. Woodcock was one of my bogey birds: species that I really should have seen but hadn’t. I have traipsed through many woods in my local area hoping to disturb one from its daytime rest, which is by far the easiest and most common way to spot a Woodcock, without any luck. Therefore I was exceedingly pleased to have finally come across one.

Soon after we flushed the Woodcock, it was time for me to head off. When I arrived back home I counted up the number of new species I had found and I was pleased that I had just made it to 2000, with Woodcock being species number 2000! Now it is time to think of a new target to keep me motivated to find more interesting wildlife. My next PSL target is to reach 3000 species by my 15th birthday in August 2018.