Catching up with the migrants

It was an early start, leaving well before dawn in order to be in place as the sun came up. Travelling up the A11 towards Norwich and passing through a series of heavy showers made the early start seem all the more ridiculous but as we approached the east coast our mood brightened, mirroring the clearing skies. By the time we reached the dunes at Winterton the weather conditions were just about perfect for picking up on the visible migration likely to be taking place, as small birds passed south on their autumn journey.

Watching visible migration can be an unpredictable pastime; earlier in the week there had been big ‘falls’ of birds much further north and we were uncertain as to our chances of catching up with good numbers of birds this far south. However, things can change and the weather conditions over western Europe were such that there should have been some good birds on the move. This unpredictability can both add to the excitement of this form of birdwatching (who knows what might turn up) and prove frustrating (with few birds passing over). It also involves a lot of standing in one spot and scanning the sky, scanning to pick out the small specks passing over and straining to hear a diagnostic call.

It did turn out to be a quiet morning, with only small numbers of birds passing overhead; a few finches, the odd wagtail and a single Tree Pipit. There were also a few Rooks, arriving singly from the east. Since we could not see the shore from our position it was not clear if these were migrant birds, arriving from the Continent, or local birds that had been feeding along the tide line. Then there was the Sparrowhawk, working its way along the dunes. Again, this could have been a passage bird, newly arrived, or it could have been a local, like us hoping to connect with some migrants. After an hour or so of watching it became clear that we should turn our attention to the bushes and shrubs that lined the back of the dune system. Here, sheltered, below the low cliff-top gardens were feeding and roosting opportunities for migrants that may have arrived the previous night. Working our way slowly south, we soon turned up a rewarding mix of birds, many of which were migrants. As well as Willow Wabler and Chiffchaff, there were Blackcap, Whitethroat and even Siskin. Spotted Flycatcher and Pied Flycatcher could be seen in the same field of view through the telescope and, in such good light, we were rewarded with a fantastic morning of birdwatching. We’ll be back again over the coming weeks to see what else we can pick up.

A place on your table?

The combination of warmth and rain over recent weeks has triggered a mass of fungal fruiting bodies to emerge across the countryside. Fairy rings of mushrooms dot many of the grassland swards around here and little groups of toadstalls adorn decaying stumps or cluster around the root balls of still living trees. Some of these fruiting bodies would make a tasty meal but knowing which requires a degree of skill and understanding. Over the years I have sampled a number of different fungi; from the meaty textured Cep through to the delicate flesh of the Parasol Mushroom and the butter-greedy Giant Puff-ball. However, my real interest remains in the natural history of these organisms rather than in their culinary value.

In particular, I have always been interested as to why some species are highly poisonous while others (even closely related ones) remain entirely edible (and rather tasty). For example, one of our most dangerous species, the Death Cap, contains a cocktail of poisons that not only interferes with some of our body’s most fundamental processes but also actively targets cell nuclei in the liver and kidneys. Death comes after a week and the species is responsible for 93% of all fungi-related poisonings in Europe; yet despite this, slugs, maggots and Rabbits all seemingly eat this toadstall with impunity. Is it a chance of chemistry that has made the Death Cap so deadly to us?

The Death Cap belongs to a wider group of fungi known as the Amanita and this group (of which we have roughly 30 species) contains toadstalls with some wonderful names. Along with the familiar Fly Agaric, there are the Panther, the Blusher, the Destroying Angel and the aptly-named Fool’s Mushroom. While some Amanita are edible (for example, Caesar’s Mushroom – which has been prized since Roman times) most are inedible and a few are deadly. Several species are considered edible after thorough cooking. The toxins of the Blusher, which attack red blood cells and cause a form of anaemia, are broken down by parboiling. The same is true of the toxins contained in the Grisette and Tawny Grisette, two species that were formally thought of as being edible without the need for cooking! The Amanita are fairly easy to identify as a distinct group because they share a number of common features that can be seen in the field. Separation of certain species within the group is, however, less easy. This is another reason why the comments made by one famous mycologist in describing these toadstalls are best followed. He noted that this is a group of fungi ‘to which it is better to devote a purely botanical interest than to give them a place on your table.’

The silent hunter

I have sometimes heard the Barn Owl referred to as ‘the silent hunter’, a particularly apt description for what is one of our most engaging birds. Many years ago I undertook a study into the habitat associations of various small mammals, the favoured prey of the old white owl, and this involved spending many hours on my knees measuring and sampling grassland habitats. The study area was part of the hunting range of a pair of Barn Owls and in some years the birds were joined by a neighbouring pair as they hunted over the ground. The birds were often to be seen quartering back and forth across the meadow, their slow flight designed to help them detect small mammals in the sward below. Every now and then one of the owls would fly right over my prostrate form, the bird completely silent as it passed within three or four feet of me. I guess that I was such a regular feature on the meadow that they had come to accept me as part of the landscape.

Silent flight is obviously important for this active hunter, allowing a close approach to the mice, voles and shrews that form the bulk of its diet. The silent flight also increases the effectiveness of the owl’s already exceptional hearing, reducing any unnecessary noise that might interfere with its efforts to secure prey. If you have ever handled a Barn Owl then you will know just how soft the plumage is, beautifully contoured to cut down on drag as the bird moves through the air. The individual wing feathers also show modifications to help reduce noise. Each of the primary feathers has a fine comb-like fringe along its leading edge and a velvety texture to its upper surface. Collectively, these features reduce turbulence as air rushes across the surface of the wing, which means less resistance and less noise in flight. The wings themselves are broad and fairly long, enabling the owl to perform its buoyant flight with surprisingly little expenditure of energy.

With the fieldwork finished I no longer see Barn Owls on such a regular basis and close encounters are now a ‘red-letter day’. However, there are a few breeding pairs in this south-western corner of the county and I still get a real buzz from seeing them. Just the other morning, a very pale individual (probably a male) was quartering a wet meadow near the village of West Stow. As it moved across the field, periodically dropping down to snatch at some hidden prey item, I felt very tempted to hunker down in the vegetation to see if it would make a close approach.

Stinking Willie

Over recent weeks the blocks of forest clearfell have been carpeted with the bright golden yellow of ragwort, not just a few plants scattered here and there, but many thousands of them. This striking spread of late summer colour, which practically glows against the backdrop of dark conifers, is a welcome sight for me, but for many landowners the ragwort is a far less welcome plant. Those who keep horses may spend many hours pulling this agricultural ‘weed’ from paddocks and pastures, hoping to spare their animals from the irreversible cirrhosis of the liver that comes from eating quantities of the plant. Interestingly, while horses and other grazing animals normally avoid eating the flowering stems, they will take it when it has died and dried out; presumably they are unable to identify the risk it poses once it has lost its characteristic colour. Curiously, sheep appear to be immune to its effects and may even relish it.

The general antipathy directed towards the ragwort can be seen in many of its local names, from ‘mare’s fart’ in Cheshire to ‘stinking Willie’ in Scotland. The latter name is a reference to the Duke of Cumberland, whose victory at the Battle of Cullodon Moor earned him the nickname of ‘butcher’. It is reported that ragwort was spread around by his troops during their campaign. Another local Scottish name for the plant is ‘wee-bo’, meaning ‘little devil’. It is clear from such names, and indeed from the reaction of friends and colleagues to the plant, that it is an unwelcome part of our arable flora. Yet, I have always associated ragwort with the cinnabar moth, whose striking black and yellow caterpillars feast upon its foliage.

Ragwort is known as ‘St. James’s herb’ in certain other countries and even here in Britain the same association has been made (through the alternative name of St. James’s wort’). This association may stem from the fact that the plant is in flower on St. James’s Day (25^th July) or, alternatively, it may have something to do with the plant being used to treat the sores and ulcers which afflicted pilgrims visiting the shrine of St. James in Santiago de Compostela (Spain). There are also references in old herbals of the plant being used as a treatment for gout, sciatica rheumatism – in each case the green leaves being used as a poultice. The ragwort has even become a national flower – the ‘cushag’ of the Isle of Man.

It is easy to dismiss the ragwort as a troublesome and unwanted neighbour. However, this ignores the long interplay between Man and plant, with the plant acting variously as weed, poisoner and healer. For me, such associations add to its fascination.

Eyes and ears for bats

Returning from the office the other evening, I stopped on the Nun’s Bridges to scan the river. It was not quite dark and there was always the possibility that I might spot one of the local Otters. Needless to say, my luck was out and no dark shape was to be seen cutting it’s way across the surface of the slow-moving waterbody. However, other mammals were abroad and I was soon entranced, watching the dancing silhouettes of a dozen or so bats as they hawked for insects low above the water. This small cloud of tiny, delicate mammals, ‘chattered’ away as they circled too and fro to snatch midges and other small flies.

The chattering calls, whose intense high-pitched pulses I can still just about pick up with my hearing, are used to target prey and derive from a technique known as echolocation. This is really a highly developed form of sonar, the bat sending out short pulses of intense sound and then monitoring the returning echo with its sophisticated hearing to build up a ‘map’ of its surroundings. Although many people are bewildered by the apparent complexity of bat echolocation, to the bat it is just another component of its sensory armoury – much like how we might view our sense of sight or taste. Bats make and hear sounds in the same way as most mammals; the echolocation pulses are generated in the larynx and the resulting echoes are picked up by their ears. Admittedly, the larynx of a bat is proportionally bigger than our own, relative to body size, because the call has to carry a great deal of energy in order to produce a useful echo. Most bats emit the echolocation call through their mouth but there are species, like the horseshoe bats, where the sound is emitted through the nose.

Because the echolocation calls of bats often differ in their core frequency, it is possible to identify the different species by the pattern of the call and the frequencies over which it occurs. For example, the calls of Daubenton’s Bat start at about 85kHz and drop to about 32kHz, with a peak in intensity around 45kHz. Simple bat detectors, which convert the inaudible calls to a frequency we can hear, can help you split bats into rough groups but more complex detectors, coupled with computer software, are needed to separate the calls of species which are similar in their outputs.

The size and behaviour of the bats hawking over the river suggested that these were one of our pipistrelle species, although there may well have been a Daubenton’s Bat or two in with them. I will have to bring my bat detector down to the river in order to find out.

Have moth trap, will travel

You know how it is when you go away for the weekend; the list of things that you need to pack. In addition to the essential clothes and toiletries I often take my moth-trap, dozens of small sample pots and various field guides to Britain’s moths. I know that I am not alone in this behaviour and there is a growing army of moth enthusiasts who not only run traps at home each evening but also seem hard to separate from their trap when they go away. Much like birdwatching, one of the joys of moth trapping is seeing something new and, since different moths live in different habitats or different parts of the country, it is easy to see the appeal of running your trap somewhere completely different.

A moth trap works by drawing moths in towards a bright light, normally a mercury vapour lamp, which produces light of a different wavelength to that of standard household bulbs. Any moths which collide with the bulb, are stunned very briefly and drop into a collecting box below. This box has a narrow entrance, so escape is difficult, and the moths soon settle amongst the pile of egg boxes added to the box to give them some cover. Early the next morning, the moth-trapper can rise from his or her slumber and check the contents of the box. Depending upon location, time of year and weather conditions the trap can contain just a few moths or it can contain thousands. After logging what has been caught the moths are released to continue with their lives.

Last weekend my trap accompanied me to my parent’s garden on the edge of a market town among the oak and beech woodlands of the Surrey/Sussex border, where a very different suite of moths from those present in my small urban garden are to be found. Sure enough, come morning there were just in excess of 170 moths in the trap of several dozen different species. Among these were common and widespread species, like Large Yellow Underwing, Brimstone and the Dunbar, but there were many others that I don’t tend to catch at home. These included my first ever Maiden’s Blush (no mischievous smirks please) and Small Phoenix, not to mention two rather stunning black and white moths known as Black Arches. I never cease to be amazed by the sheer diversity of moths, the combination of shapes, sizes and colours. Most casual observers, encountering the more familiar moth species, will be completely unaware of just how beautiful many of our moths our. If you have never seen the results of a moth-trapping session then I urge you to go along to a local moth-trapping evening. You will not be disappointed.

A fortunate find

The Slow-worm is one of those creatures which I rarely stumble across these days, perhaps because it spends the greater part of the year hiding underground or in deep cover. Being ‘cold-blooded’ the Slow-worm tends to thermoregulate by keeping its body in contact with warm surfaces. While our three snakes tend to bask out in the open, the Slow-worm will often warm itself by settling under a piece of tin or other refuse that absorbs the sun’s warmth. Of course, it is with the snakes that the Slow-worm is sometimes confused; despite its cylindrical body and absence of external legs, the Slow-worm is not a snake but a harmless ‘legless’ lizard. Unfortunately, ignorant householders, panicked by the ‘snake-like’ appearance, may soon dispatch any Slow-worm that turns up in their garden. This is not only bad for the Slow-worm but also for the gardener, because Slow-worms eat good numbers of common garden pests, like slugs. Slow-worms differ from snakes in having a visible eyelid and smooth body scales. In addition, the cylindrical body shape is uniform along most of its length, whereas in a snake there is a clear narrowing behind the head to produce a discernable ‘neck’.

Hibernation ends in March and throughout the spring adult Slow-worms indulge in breeding. Mating is a fairly aggressive affair, with the adult males grabbing and holding females by their head. The resulting young are ‘born’ in September or October, hatching from their eggs almost immediately they are laid, giving the appearance of live birth. These young Slow-worms are just eight or nine centimetres in length and have the colour of newly minted metal. As adults they become a shiny metallic grey-brown, like well-aged bronze, often with thin longitudinal stripes of chocolate brown. Some of the older males are adorned by a pattern of pale blue spots, scattered along their head and flanks.

My most recent Slow-worm encounter happened just the other week and was unusual in that the lizard was out in the open, part way across a gravel track. I normally encounter them when turning over sheets of corrugated tin or refuse on areas of rough grassland or heathland. This particular individual had clearly shed its tail at some point in the past, either lost during courtship or shed to distract a would-be predator. The tail is physically shed (as opposed to being pulled off) by the lizard, muscular contractions pulling apart the tail at a point of fracture within the vertebrae. Once shed, the tail will flex and spasm for several seconds, sufficient distraction for the lizard itself to slip away. I managed to take a few photographs and then the Slow-worm was gone, disappearing into thick cover.