Are Yew poisonous

Our bathroom has some intimacy with a large Yew tree (Taxus baccata), the fulsome evergreen branches hanging a metre off the window unnoticed for much of the year. But in the autumn the multitude of mini matt red barrel-shaped berries colours up this dark patch of garden. This week whilst attending to some toiletry I noticed two squirrels feasting on the yew’s fruit. Having always heeded the warning that almost every part of the yew tree is poisonous, I was curious at how these animals coped with the toxins, or wondered if the tree was as dangerous as we are led to believe. Indeed it opened up a bigger question; how do animals know what is and isn’t poisonous?

Numerous scientific studies have determined that most tissue of the yew tree, including the seeds and foliage are rich in taxin(e), a complex mixture of toxic alkaloids (Thomas & Polwart, 2003), and hence it’s genus name of Taxus. The toxins appear to impact primarily on the cardiac tissue of humans and other mammals, leading to heart failure and potentially death. Other effects reported in humans include dizziness, vomiting, abdominal pain and convulsions (Wilson, et al., 2001). This toxicity remains prevalent all year round and even when dried, but peak concentrations are found during the winter (Wilson, et al., 2001). Most incidents of poisoning appear accidental occurrences, with contaminated feed to livestock, but there are a few human reported cases.

The poisonous nature of the Yew has been known for ages. Primitive cultures made use of yew juice dipped arrows as an animal poison for hunting and the Celts committed ritual suicides by drinking extracts from yew foliage (Wilson, et al., 2001).

However, interestingly there is one part of the tree that does not contain taxin which may well explain the recent diet of our squirrels; the aril, or soft succulent scarlet tissue surrounding the seeds and forming the berry. So our ever-clever squirrels can enjoy the fruitful bounty of yew without toxic effect, but I wonder what they do with the seeds – do they spit them out or pass them out undigested in a parcel of ready-made fertiliser. This seems like a clever strategy of the yew to direct wildlife to only consume those parts of it that aids its seed dispersal. However for us humans, BEWARE -only the wiliest of wild foragers should attempt to eat the yew berries, ensuring none of the deadly seeds are consumed.

Thomas, P. A. and Polwart, A. (2003) Taxus baccata. Journal of Ecology, 91( 3): 489-524.
Wilson, C. R., Sauer, J. and Hooser, S.B. (2001) Taxines: A review of the mechanism and toxicity of yew (Taxus spp.) alkaloids. Toxicon, 39 (2-3): 175-185.

The Upside-down bird

We recently started feeding our woodland birds again after a summer break, and within hours of filling peanut & fat ball hangers they were back as if there had been no break in supply. The feeders are being dominated by the tits, including; Great, Blue, Long-tailed, Coal & Marsh. Many of these are likely to be new to the ‘Pinfold café’ after last year’s harsh winter.

The tits have been joined this autumn by at least two regular Nuthatches (Sitta europaea). I’ve seen these birds many times scurrying up and down tree trunks, but I’ve become intrigued recently by their apparent preference for feeding upside down, particularly on the hangers. This reverse mode is relatively unique to Nuthatches. Their natural foraging technique involves working their way down tree branches looking for invertebrates, before flying to the top of another tree and repeating the exercise. The only explanation that I can find for such novel feeding is that by adopting a different approach they see invertebrate prey that other birds, such as woodpeckers and treecreepers, overlook from more conventional angles. Nuthatches appear to be aided by having an extra-large and stronger hind toe (hallux) for gripping the trunk at tight angles, and a stubby tail to reduce a potential incumbency. Perhaps they get so used to this productive technique that they continue to feed upside down on hangers through habit rather than efficiency. Their characteristic posture on the hanger is body facing downwards but frequently looking upwards checking for threats (see photo), making for a rather rubber-necked pose.

It is therefore no surprise that due to the modus operandi of the Nuthatch, that they are frequently known as the ‘Upside down bird’. Other species of Nuthatches from around the world feed in a similar way, which have prompted other nicknames, including Topsy-turvy bird, and Devil down-head.

Spring lunacy

At the beginning of September I attended a course in Pembrokeshire on rocky shore invertebrates. The course was carefully timed to coincide with the largest ‘spring’ tide of the year so that we could explore the furthest point of the lower shore. The term ‘spring tide’ has actually no connection with the season but is derived from the Saxon ‘springan’, “to bulge” or “to rise”. The dictionary definition is “the rising of the sea (to an exceptional height) at particular times” (Onions, 1952). These “exceptional” tides are caused by the combined gravitational effect of the sun & moon every two weeks at a new and full moon. The largest ‘spring’ tide occurs near the equinox during September when the sun and moon are most closely aligned and so referred to as an “equinoctial spring tide” (Oakley 2010). A similar tide occurs around the March equinox.

(Photo of Painted Topshell above - Image credit: Asbjørn Hansen via http://www.flickr.com/)

This is therefore a very special time for the seashore naturalist, when animals and plants are so rarely exposed for observation. On my visits to rocky shores near Dale Fort, large kelp forests were exposed dotted with Blue-rayed Limpets (Patella pellucidum); small flattened versions of the Common Limpet (Patella vulgata) found high up the shore and characterised by brilliant iridescent kingfisher blue lines across their dorsal surface. Painted Topshells (Caliostoma zizphinum), the most colourful of this group of sea snails looking like vibrant spinning tops were found amongst amid rocks encrusted with brightly coloured star ascidian colonies, looking as alien as their name suggests . Crabs were also revealed, more typical of sub-littoral habitats (below shore level), such as the pie-crust edged Edible Crab (Cancer pagurus) and dirty looking Broad-clawed porcelain crabs (Porcellana platycheles). Most exciting was a Decorator crab (Macropodia sp) covered in little seaweed tufts in an attempt to camouflage itself, and a small skeleton like sea-spider scuttling along the tide line at its lowest point.

(Photo of Edible crab above - Image credit: Christophe Quintin via http://www.flickr.com/)

It was a fantastic opportunity to capture a rare glimpse of such wildlife, but all too soon the tide turned and they became submerged again beneath the advancing waves, some not to be exposed again for perhaps many months.

Why not book your place soon for the next equinoctial spring tide at a rocky shore near you!

Oakley, J. (2010) Seashore Safaris. Cardiff: Graffeg Books
Onions, C.T (Ed) (1952) The shorter Oxford English dictionary on historical principles. 3rd ed. Oxford: Oxford University Press.

Doing the Dodder dance

Whilst on holiday in Devon I met up with a wildlife friend to visit a nature reserve, Chudleigh Knighton Heath, near Bovey Tracey. This SSSI site of predominantly acid heathland is managed by Devon Wildlife Trust (DWT). However it took a good hour to get onto the site proper due to the initial distraction of the local herb-rich roadside verges. Damp ditches were particularly productive including Lesser Spearwort (Ranunculus flammula), Water Mint (Mentha aquatic) and Sneezewort (Archillea ptarmica). Sneezewort is a close relative of the more ubiquitous Yarrow (Archillea millefolium), being named due to its past use as a sneezing powder (PFAF, 2010) which provides its Latin name ptarmica, derived from the Greek ptario meaning ‘sneeze’.

On the reserve itself we quickly found three members of the heath family; Bell Heather (Erica cinera), Cross-leaved Heath (Erica tetralix) and Heather itself, also known as Ling (Calluna vulgaris). We also found several specimens of Lousewort (Pedicularis sylvatica), a curious plant with over-proportioned flowers and ecologically, a grass parasite akin to the closely related Yellow Rattle (Rhinanthus minor). But then suddenly my friend Greg dropped onto his knees and started to feverishly investigate a patch of Heather. Breathing excitedly and through snatched breaths he managed to stammer “Dodder”. He then stood up and provided a pre-emptive apology, before performing a rendition of a ‘Rumpelstiltskin’ hopping dance upon the heath, a means to release the sheer and utter joy of seeing such an exquisite and (our) first sighting of this species. Dodder (Cuscuta epithymum) is indeed a wonderfully interesting species, parasitising typically heather and gorse. Lacking chlorophyll and with vestigial leaves, they cover their hosts in a mass of intertwining threadlike red stems and pink clusters of flowers. It is however now uncommon in the UK, having declined significantly during the past few decades due to habitat loss. There is evidence that it does benefit from habitat management such as grazing or burning as this provides more young Heather plants, its preference (Meulebrouck, et al., 2007). DWT do now have an active management programme including scrub clearance, light grazing and rotational burning, which may well be benefiting Dodder.

A few days later I was walking part of the Cornish coastal path near Boscastle and there to my delight was another mass of Dodder, but this time on a patch of Gorse (Ulex europaeus). I managed to resist the temptation of doing the ‘Dodder Dance’ being in a more precarious position, but silently toasted Greg and smiled at recalling his exuberance.

For better images of Dodder, see http://luirig.altervista.org/naturaitaliana/viewpics.php?title=Cuscuta+epithymum

Meulebrouck, K., Ameloot, E. , Verheyen, K. and Hermy, M. (2007) Local and regional factors affecting the distribution of the endangered holoparasite Cuscuta epithymum in heathlands. Biological conservation, 140 (1):8 -18.

Plants for a Future (PFAF) (www.pfaf.org)  

Unbelievable umbellifers

An umbel is an inflorescence made up of many individual flowers on stalks (pedicels) that originate from roughly the same point on the flowering stem (peduncle) giving the appearance of an umbrella. The umbellifers all share this characteristic, usually with white or yellow flowers with rounded or flattened tops, with the appearance from above of complex lacework. The British Iles is home to over 50 species, ranging widely in size and usefulness. They are more commonly referred to as the ‘carrot’ family (Apiaceae), and include a number of edible garden plants in addition to the carrot, including fennel, coriander, parsley and celery. However more unusually, the Pignut (Conopodium majus), was once commonly dug up for its edible tubers. Indeed evidence that they were collected as a wild food and possibly used in a ritual context, would appear to date back to the Bronze Age, in addition to the now nationally rare Great Pignut (Bunium bulbocastanum) (Moffett, 1991). But many of the umbellifers are far less agreeable and some considerably poisonous.....

......Many people are familiar with Giant Hogweed (Heracleum mantegazzianum) and its poisonous sap, which when combined with sunlight causes severe blistering to skin. The red/purple spotting on the stem is a useful warning shared by other poisonous umbellifers, such as Hemlock (Conium maculatum) and Rough Chervil (Chaerophyllum temulum). To illustrate their potency, one report of dairy cattle inadvertently consuming Rough Chervil caused severe internal haemorrhaging amongst many other symptoms, leading to their slaughter (Fejes, et al., 1985).

But it is the ubiquitous Cow Parsley (Anthriscus sylvestris) that is probably the most familiar umbellifer out of the garden, adorning our country lanes and roadsides with their tall frothy inflorescences from April to June. Now in July they are brown and ageing, their flowerless umbels resembling old broken umbrellas.

I’ve seen most of these umbellifers this year, but there is one that I am unlikely to come across – a protected species, Shepherd’s- needle (Scandix pectin-veneris), listed as critically endangered by the World Conservation Union and has its own Biodiversity Action Plan. This seems somewhat ironic as it originated as a grain contaminant from the Mediterranean establishing itself for generations as a common weed of cornfields.

So when you next spot an umbel look a bit closer, but check first for purple spots, or maybe dig for wild pignuts like our ancestors.

Fejes, J. et al. (1985) Chaerophyllum temulum [temulentum] poisoning in dairy cows. Veterinářství, 35 (2):68 -69
Moffett, L. (1991) Pignut tubers from a Bronze Age cremation at barrow hills Oxfordshire England UK and the importance of vegetable tubers in the prehistoric period. Journal of Archaeological Science, 18 (2):187 -192

There and Back again

There and Back again (better known as ‘The Hobbit’ by Tolkien)

(Image copyright of Andrew Easton)

A couple of weeks ago I was watching BBC Springwatch on iPlayer with my youngest, with the presenters introducing a new bird for the series, when a movement caught my eye out in the garden through the window. A dusky, non-descript bird flying repeatedly back and forth to the same perch on a warm summers evening - it could only be the Spotted Flycatcher (Muscicapa striata), the same bird Peckham & Dumble were so proudly talking about. Coincidental! This hunting behaviour is unique in birds, having been described as the only such species that is a ‘sit-and-wait’ predator of aerial insects (1). It can also be identified by a characteristic upright stance and the streaked markings on the forehead – it is the young that are more truly spotted.

Last year we had a pair of Spotted Flycatchers try and nest in the Wisteria on the South-facing wall of the house, but without success. So it was reassuring to see them back this year, a late migrant from Southern Africa. They are a bird in some crisis, with growing conservation concern following a period of prolonged and accelerating decline of over 50% in the UK over the past 25 years (2), putting them high on the at danger ‘Red List’. The factors affecting the population decline is still unclear, but it does appear to be broad-scale, affecting populations in all habitats and regions equally (2).

As a child I used to look forward every summer to visiting my grandparents in the Cotswolds and seeking out these birds near a small sewage treatment site, where they used nearby barbed wire fencing as a perch to hunt from. Now here in 2010, as I watch and show my daughter these precious birds flying back and forth from favourite perches, I wonder if she will have the same opportunity with her children - For that, these and others will have to fly there and back again many times, both to catch millions of insects and travel repeatedly across continents.

(1) Davies, N.B. 1977. Prey selection and the search strategy of the Spotted Flycatcher. Animal Behaviour. 25: 1016–1033.
(2) Freeman, S.N. & Crick, H.Q.P (2003) The decline of the Spotted Flycatcher Muscicapa striata in the UK: an integrated population model. Ibis, 145:400–412

Hoary Quaking Tongue and Ragged Adder Rattles Black Medick

These are colourful words of an English summer meadow, surprising and mysterious. Last Saturday on a hot and sultry afternoon I joined a local guided walk of Potwell Dyke Grasslands tucked behind the Minster in Southwell, on a discovery of 'magical' plants with their vibrant names.

As we approached the site up a narrow lane, the first surprise to be revealed was the Greater Celandine (Chelidonium majus); not a celandine at all, but a poppy with its small yellow flowers superficially resembling the latter more closely. On the site, Yellow Rattle (Rhinanthus minor) was in abundance, so named due to its loose seeds that rattle in the dry fruiting capsules. It is actually a parasite on other plants such as grasses and has been considered a harmful meadow weed by reducing agricultural productivity (Westbury, 2004). However this suppressive impact on grasses has been turned into a virtue for conservation as it also improves biodiversity of hay meadows.

As we moved into the main meadow we were presented by a purple swathe of Southern Marsh –orchid (Dactylorhiza fuchsia) with a backdrop of yellow buttercups, and red Ragged Robins’ (Lynchnis flos-cuculi) (see image). The latest exciting species find in this meadow is Adder’s Tongue, a fern from the Ophioglossum genus, named from the Greek ‘snake-tongue’ due to its narrow spore-bearing spike. Ironically rabbit disturbance of the soil seems to have helped it take hold, perhaps mimicking dune-slacks, one of its favourite habitats.

The adjoining meadow displayed more delights with Bulbous Buttercup (Ranunculus bulbosus), Black Medick (Medicago lupulina), blue Bugles (Ajuga reptans), Hoary Plantain (Plantago media), quaking grasses and the diminutive Pignuts (Conopodium majus). All quite a show and apparently it gets better later in the season. No doubt I will be back to see the orchids mature and to experience more colour and plant mystery.

Westbury, D. B. (2004) Biological Flora of the British Isles, No. 236. Rhinanthus minor L. Journal of Ecology, 92 (5):906-927.

Close shave for Twayblades

Today I went to look for a local green orchid, the Common Twayblade (Listera ovata). It is probably named “from Old Norse, since the modern Swedish name is Två Blad - two leaves” - Typically plants have two dark green oval leaves (1).












This particular plant has been saved from the ‘cut’ by a local botanist, having been topped a few weeks ago by a council mower. It has been protected from further damage with sticks and tape. Our Council seems to have a growing obsession with scything our local roadside verges and hedgebanks. Maybe people prefer green grass monotony or barren banks scraped to the earth. Clearly there needs to be some maintenance, but why so zealous? What is sacrificed for this ‘clean’ countryside approach is a razzmatazz of wild flowers. The plants that have adapted to this manmade habitat are many of our woodland flowers utilising the shade of hedgerows or overhanging trees, and other meadows plants

using the more open aspects. These plants also provide food and cover for many of our invertebrates. Locals have also spent the last seven years protecting a ‘colony’ of Six-spot Burnet (Zygaena filipendulae) moths on the verge opposite to the Twayblades, feeding on the richness of Knapweed, Trefoil and Vetches.

However we are in danger of losing much of this bonus biodiversity. It takes up to 15 years for a Twayblade plant to reach maturity from seed(1), making it hard to rectify damaging actions. Ironically there is evidence that the Common Twayblade rather enjoys manmade habitats(2), but I doubt this is true where the ‘countryside hairdressers’ are allowed to run riot with their blades.

(1) Britain’s Orchids (http://www.britainsorchids.fieldguide.co.uk/)
(2) Nowicka-Falkowska, K. (2002) Ecology of selected populations of Listera ovata (L.) Br. from Siedlce environs. Acta Scientiarum Polonorum - Biologia, 1(1): 23-32

Hawthorn styles

It’s the time of the May-flower or Hawthorn (Crataegus monogyna). The hedges and country lanes about my home are now full of their white blossom true to their name. This is a plant full of mystery, such as a link to the early Christians who associated it with Joseph of Arimathea (owner of the tomb given up to Jesus after the crucifixion) (1); It is said that he visited Glastonbury where he planted a staff that sprouted to produce a ‘Holy Thorn’ that blooms around Christmas time, and from which cuttings have grown and still occur in the area (2).

But until this spring I was unaware of another, more botanical mystery. Mary, a local botanist popped in to see me this week with a cutting from what she called ‘Two-styles Hawthorn’. This is actually an alternative name for the Midland Hawthorn (Crataegus laevigata), although I prefer its more apt original name. This is a less common species of hawthorn and is characterised by having two or three styles compared with the Common Hawthorn’s single style (hence the second part of its Latin name, monogyna). During the autumn they can still be distinguished by crushing the ‘haws’ and counting the seeds; if there is more than one seed it will be a Midland Hawthorn, reflecting the flowers style number. Its leaves are also different with the lobes far more rounded and less deeply cut to the mid-rib. It is true that it occurs commonly across much of the Midlands, but it is also as frequent in the South East. However beware as the differences can get rather blurred as they frequently cross to produce hybrids. Otherwise the Midland Hawthorn tends to bloom earlier and prefer more shaded woodland.

So next time you are admiring may blossom, have a closer look and check out the styles. It gets a bit addictive - although my neighbours are getting increasingly suspicious of my actions.

(1) Filed Guide to Trees and Shrubs of Britain (Reader’s Digest Nature Lover’s Library)
(2) http://www.mystical-www.co.uk/glastonbury/hawth.html

Poisonous claws and gonopods

I’ve recently attended two courses looking at invertebrates, and focussed on the ultimate ‘creepy crawlers’, millipedes and centipedes; the many legged creatures that derive their names from the Latin for foot, ‘pedis’.

It’s been fascinating looking in detail at these mini-beasts, including poisonous claws and gonopods (genitalia). There is frequent confusion between the two groups, with an assumption that millipedes have many more legs than centipedes. This is true in some cases, but the key differences are that Millipedes have two legs per body segment (hence their classification as Diplopoda), whereas centipedes have only one (Chilopoda). Otherwise there is great variety in leg numbers, even within species, from the fast surface scurrying ‘stone centipedes’ (Lithobius species - see image above) with 15 pairs to long winding ‘earth centipedes’ (Geophilomorpha) with up to 101 pairs. Millipedes include those that roll up into a tight ball (the Pill Millipede, Glomeris marginata) , and the snake millipedes with their numerous legs enabling them to glide over the surface like their namesake and also often curl into snake like spirals when disturbed. All centipedes are carnivorous using their poisonous claws, an adapted leg, to immobilise their prey. In contrast the millipedes are primarily feeders of leaf litter and dead wood, playing an important role in breaking down leaf litter. The millipedes can also be long lived, such as the Pill Millipede which has been recorded as living for 11 years (*).

The best places to find them are under logs & stones and in leaf litter in woods and gardens. I've found all the above types in my garden in the last two days. Just lift up pot or stone and see what’s there – but please don’t forget to place things back to where you moved them from as you may destroy a mini-home and its long-term tenants.

*To identify and read more about these animals and many others that can be found in similar places, try ‘Animals under logs and stones’ by C.Philip Wheater & Helen Read (Naturalist Handbook series, number 22).