Monthly Archives: May 2013

Stonechats on Brean Down

I took these photos of a female (left) and male (right) European Stonechat (Saxicola rubicola) on the north-facing slope of Brean Down yesterday afternoon. Over most of our region Stonechats only occur in the winter and on migration, but there is a small breeding population of around 10 pairs in the western Mendip Hills, with the greatest concentration on Blackdown, their highest point. Pairs are seen in summer on Brean Down most years, and the habitat certainly looks suitable for a nesting attempt.

046 048

Stonechats of one kind or another are found virtually throughout the entire Old World. Their treatment as either full species or races of the same species follows a pattern seen in many widespread species: originally, prior to the twentieth century, each slightly different-looking form of Stonechat found in a new part of the world was described as a new species. Then, following changes in biological thinking in the mid-twentieth century, it was proposed that all of the different stonechats (from birds in South Africa that look like this, to birds in Europe like those above, to birds in south-east Asia that look like this) were in fact all one species, comprising 25 races.

In the last couple of decades, decisions like these have been re-evaluated in the light of new data, and the stonechats are one group that has been unpicked as a result. The mid-twentieth century ‘lumping’ into one species has been replaced by a three way split into African, European and Asian species. The position with the Asian stonechats could well be more complicated and when more detailed studies are done on the Asian races, some of them may be split further.

Bird’s-nest Orchids in Lower Woods

Vic Savery kindly sent me this excellent photo of a Bird’s-nest Orchid (Neottia nidus-avis), one of a group of six he found today in Lower Woods, near Wickwar. The plants were in either Gibbons Trench or Horwood Trench, two paths which run west from the main north-south ride (see the reserve map here). Bird’s-nest Orchid is found in several scattered woodland sites around Bristol, usually in small colonies like the one Vic found today. The situation is much the same in Somerset and Wiltshire, but it becomes more common in the Cotswolds, the Forest of Dean and the Wye Valley.

birds nest orchid 9
Bird’s-nest Orchid, 27 May 2013, Lower Woods, Gloucestershire, Vic Savery (naturenutz.net)

Bird’s-nest Orchid obtains its nutrients from a species of Sebacina fungus, which lives in the root system of the orchid and in turn receives its nutrients from nearby tree roots, The relationship between the fungus and tree is a two-way partnership: the fungus passes minerals back to the tree. The orchid however, gets a nutritional free ride. In many sites, the host tree is Beech (Fagus sylvatica), although in Lower Woods, it is presumably Hazel (Corylus avellana). Anyway, because of all this, Bird’s-nest Orchid doesn’t need any of the green photosynthetic chlorophyll molecule, hence its characterstic pale brown colour. No other similar-looking British woodland plant species is at its flowering peak at this time of year: Toothwort (Lathraea squamaria) is well past its best, and Yellow Bird’s-nest (Monotropa hypopitys) is still underground.

For more of Vic’s photos, take a look at his website.

The Avon Gorge: Bristol’s botanical bucket-list site

073 021

On the western edge of the city of Bristol is a nationally important site for wild plants. The Avon Gorge is home to over 500 plant species; as well as whitebeam trees which are found here and nowhere else on Earth, the gorge has two plant species – Round-headed Leek (Allium sphaerocephalon) and Bristol Rock-cress (Arabis stricta) – that are found nowhere else in Britain, and over twenty other nationally rare or scarce species. Peter Marren, in his book Britain’s Rare Flowers listed it as one of the top four sites in England, alongside Upper Teesdale, the Lizard in Cornwall, and the East Anglian Breckland. There can’t be many British botanists on whose bucket-lists a visit to the Avon Gorge doesn’t feature.

Given that I live fifteen minutes away by car from the gorge, you would have thought I’d spend vast amounts of time there each summer and would know the place inside out. In fact, I have tended to spread myself much more equally across the city’s wildlife sites, and so to date haven’t really given the gorge the attention it deserves. Now that I have this blog to write, something tells me that will change.

This afternoon I explored the Black Rocks area of the gorge, which is below the viewpoint on Bristol Downs called Sea Walls (see the map below for the location). The viewpoint is surrounded by sheer cliffs on three sides, but part-way down on the southern side, these give way to a limestone grassland slope with scattered rocky outcrops, altogether covering about a quarter of a hectare. I climbed the steep path which runs up the slope from the car park by the A4 Portway road. The photos at the top of this post show this part of the gorge viewed from the car park, and a close-up of a small part, to give you an idea of the species-richness of the grassland here.

Here are some of the plant species I photographed today. Going clockwise from top left, we have Basil Thyme (Clinopodium acinos), Common Rock-rose (Helianthemum nummularium), Bloody Crane’s-bill (Geranium sanguineum) and Fairy Flax (Linum catharticum).

023 004
031 040

Common Rock-rose and Fairy Flax are widespread species in limestone grassland sites around Bristol, By contrast, Basil Thyme, although found widely throughout the gorge, has been recorded at only one other site in Bristol, near Blaise Castle, and at only about five other sites surrounding the city, Slightly farther afield, it is more common in the Mendips, where its rocky limestone grassland is in greater supply, and also on the Cotswolds and Salisbury Plain.

Bloody Crane’s-bill is the rarest of these four species locally. Other than in the Avon Gorge, it is only found as a native species in Cheddar Gorge and in the Wye Valley, although it also occurs as a garden escape or a deliberate introduction in a handful of places. Unlike Basil Thyme, whose British range is centred on south-eastern England, Bloody Crane’s-bill is a more northern plant; Bristol is on the south-eastern edge of its native range in Britain.

Bristol’s new mayor, George Ferguson, has recently suggested that the Avon Gorge could be put forward to UNESCO as a proposed World Heritage Site, although interestingly, only on cultural grounds, because of the presence of the Clifton suspension bridge, rather than because of its natural features. Britain’s current suite of World Heritage sites only contains one location that qualifies under both cultural and natural criteria (the island of St Kilda off the northwest coast of Scotland), but I think a good case could be made for the Avon Gorge too. See what you think: the criteria are here.

Yellow-barred Brindle

Yellow-barred Brindle

This is a Yellow-barred Brindle (Acasis viretata), which I found sitting on (rather than in) my moth trap this morning. I’ve not been running the trap much yet this year: many nights have just been too cold, and on the warmer nights when I have run it, it has pulled in very few moths. Hopefully this should start to change soon, and I can add more moth-related posts.

Yellow-barred Brindle is quite a widespread moth, occurring in woodlands, gardens, and areas with hedgerows, but in my experience only tends to turn up at moth traps in low numbers; I’ve only ever trapped single individuals here. In the south of England it is bivoltine, i.e. there are two generations per year: adults emerge in May to June, and then again in September to October. Unlike some moths, it’s not particularly choosy over its larval foodplant: many common shrub species are suitable.

It’s a member of the Geometridae, the second most species-rich family of larger moths in Britain. Almost all moths in this family hold their wings flat at rest, and many of them hold them back in the distinctive upside-down heart shape which this Yellow-barred Brindle is resting in. Some moths in other family have simiar resting positions, but you’ll be correct 9 times out of 10 if you narrow your search to the Geometridae when faced with an unidentified moth that looks like this. There are relatively few moths that are bright green in colour like Yellow-barred Brindle, so that helps the identification process enormously. Note though that the green colour is at its most intense in fresh specimens and fades to yellow quite quickly.

There are two excellent websites which contain large collections of photos of British moths: UKMoths and UK Lepidoptera: see the Web resources page for details.

Stockwood Open Space

Stockwood Open Space is a large area of land between Brislington and Stockwood, on the south-east edge of the city. It covers the slopes which lead down from the Stockwood plateau, and some flatter ground below these. Much of the site is grassland or rank vegetation, but there are also some excellent overgrown hedgerows, bushes, and strips of woodland. Here are some photos to give you a feel for the place:

017 008

The meadows come into their own later in the year. At this time of year there are fewer plants in flower, but here are two of the more conspicuous species.

Cowslip (Primula veris):026 Bugle (Ajuga reptans):042

Here’s the location on a map. The site stretches from Whittock Road in the west to Scotland Lane in the east. I usually park at the northeast end of Stockwood Road and walk in from there.

Slender Speedwell

This is a patch of Slender Speedwell (Veronica filiformis), which I photographed by the footpath alongside the River Frome near Frenchay this afternoon.

 Slender Speedwell for blog 1  Slender speedwell for blog 2

Like its more common relative, Common Field Speedwell (Veronica persica), Slender Speedwell is not native to Britain. Originally from Turkey, it was introduced into Britain in 1808 as a rock garden plant, although was not widely grown until the 20th Century. It has since become widespread, with the only significant gap in its British distribution being in the highlands of Scotland. In Britain, it is often found as a lawn plant, and tends to spread from mown cuttings, rather than seed.

Like Common Field Speedwell, Slender Speedwell has relatively large (for a speedwell) pale blue flowers, each with a whitish lower petal, and these are arranged singly on the end of long thin stalks (pedicels) arising from the leaf-axils (the point where the leaf-stalk, or petiole, joins the main stem). The pedicels of Slender Speedwell are much longer than those of Common Field: at least twice the combined length of a leaf and its petiole. Also, the leaves are round to kidney-shaped, compared with Common Field’s more oval or pear-shaped leaves. The mat-forming habit and bright green leaves are also good clues to its identity.

For more images of Slender speedwell (and all the other British speedwell species), take a look at the links on the Web Resources page.

Ancient Woodland Indicators

One of the good things about Bristol is that you’re never very far away from a wildlife-rich place within the city itself. Over time, I aim to introduce you to as many of these as possible on this blog.

This time of year is when our local woodland sites are at their best: I’ve been to several of them recently, including, this week, St Annes Wood, which is just to the south of the River Avon, between Brislington and St Annes, in the valley of the Brislington Brook, here:

This is a site with quite a number of Ancient Woodland indicator plant species. Here are some photos of one of them, Ramsons (Allium ursinum), also known as Wild Garlic, a very apt name given the smell it gives off. In some places in our local woodlands, Ramsons forms large single-species stands, as in the left hand photo.

 Ramsons for blog 2 Ramsons for blog

In the 1980s, the Nature Conservancy Council (one of the predecessor bodies of Natural England) produced lists of Ancient Woodland indicators (AWIs) for several English regions. There has also more recently been an attempt to draw up a specific list for Somerset. These lists were limited to the well-studied vascular plants, not including ‘lower’ plants such as mosses. The lists are intended as a simple heuristic method for measuring the ecological continuity of a woodland: they consist of species which thrive well in woodland which has been undisturbed for a long time, and are slow to colonise more disturbed ‘secondary’ woodlands. So, the more AWI list species you have at a woodland site, the greater the likelihood that this woodland has a long continuous history as woodland, and therefore the greater the likelihood that other species of plant, animal and fungi dependent on continuously managed woodland are present too.

See the Articles page for details of articles about the Nature Conservancy Council and Somerset AWI lists.