A March Moth (Alsophila aescularia) and The Yellow Horned Moth (Achyla flavicornis)

I am an amateur naturalist trying to discover everything that lives in my garden.

In my last posting I described my newly home-built moth trap. I’ve been operating it for only a week, and although we’re still in chilly-March here in Oxfordshire in the U.K., I’ve already ‘discovered’ a further half dozen species to add to the seventy-five living things I’ve already reported on this blog. Normally I give each species its own posting. I’m beginning to think however, not least with summer’s ‘bounteous harvest’ approaching, that it’s likely I’ll find so many night- flying insects I’m going to need to relax this rule if I’m to stand any chance of cataloguing my garden life in a realistic time frame.

Why is it that some - although interestingly, by no means all- species of moth are attracted to artificial light? The late, great moth expert Professor Michael Majerus had a wonderfully concise answer in his book Moths (The New Naturalist Library):

“I do not know”!

A common hypothesis is that moths, some of which navigate by the distant moon and stars, are fooled into trying to navigate by the artificial light. Possibly this is the answer, but if true you might reasonably expect to see moths approaching lamps in a navigational fashion via orbital, in-spiralling flight paths. Watch a moth approach a light trap however, and I have to agree with Majerus, it’s not easy to convince yourself you’re witnessing 'navigation-in-action'. Moths often fly directly towards the light, flutter around it in seemingly haphazard ways, or seem content to settle some distance from it.

Hsaio has put forward (Jour. of Insect Physiology, Vol. 19:1971-76, 1973) an alternative theory that point light sources ‘interfere’ with the operation of moths’ compound eyes causing them to perceive regions of darkness (i.e. good places to hide) around a lamp where there are none. Again, Majerus isn’t convinced. Another of nature’s mysteries! Maybe a reader here has a comment?

To the moths themselves: Firstly, attracted to my light about a week ago, the moth in photo 1. I struggled to identify this one at first, but then caught sight of a photo of The Yellow Horned (Achyla flavicornis), in a slim photo-guide (G.Hyde, British Moths, Jarrold Colour Publications) I’ve had since I was a boy. The larvae (you can find a photo on Ian Kimber's excellent UK Moths site) feed on Silver and Downy Birch from mid-May to July before pupating to over-winter and emerge as the adults found from late-February to mid-April. I read that the Yellow Horned is a member of the Thyatiridae family of moths represented by only nine species in the U.K.

On the same evening, photo 2, a March Moth (Alsophila aescularia), the green larvae of which (again, photo's available on Ian Kimber's site) feed on many broad leaf trees including Oak, Willow and Birch. The adults fly from late February to April and over-winter as a pupae. The March Moth is notable for being one of a small number of moth species where the female is flightless. You can find a photo of a wingless female here.

Why it is that a small number of moths can ‘get away’ with having no wings, whilst all the rest expend precious energy growing them is...yep you guessed it...another of mother nature’s mysteries...at least, it is to me. Comments anyone?

Oak Beauty Moth Biston strateria

I am an amateur naturalist trying to discover everything living in my garden.

In my last posting on the Song Thrush I introduced my home-made camera 'trap' and mentioned that this gadget was one of a number I've been cobbling together:

Ladies and Gentlemen, a round of applause please for... (photo 1) ...the Skinner/Walloon Moth Trap!

One of a number of moth trap designs you'll find on the web, the principle of the Skinner trap is simple enough: A lamp to lure the critters towards a box fitted with a 'lid' comprising two sloping sheets of plastic that don't meet in the middle (leaving a gap of about ~1inch) . The moths flutter around the lamp, land on one of the slopes and slide into the box below, whence they aren't smart enough to find their way out. A few egg-boxes give them somewhere to hide.

To best attract moths you need a lamp that peaks towards the blue/ultra-violet. Best is a mercury vapour- or so-called actinic-bulb (you need the correct electronics (a 'ballast') to power either incidentally). I bought the various bits I needed from the Entomological Wildlife Group.

And the result?

After an evening spent excitedly watching my moth trap through my kitchen window...photo 2! (In acquiring the photo, I let the moth out of the trap and it alighted on my house wall incidentally).

Twenty minutes spent flicking through my copy of Moths (Waring and Townsend, British Wildlife publishing) and I'm confident I've met an Oak Beauty (Biston strateria).

The Oak Beauty is a member of the Geometridae family of moths of which there are some 20,000 known species with 300 occurring in the British Isles. Geometridae is from the same stem as geometer and is a reference to the measuring, 'inch-worm' gait of these moths in the larval stage. The caterpillars of the Oak Beauty feed on Oak, Hazel, Alder, Aspen, Elm and Sallow. They are well camouflaged to resemble twigs. I've never myself seen one, but you can find a photo of one here.

The moth I caught was a male, as indicated by his impressively large, feathery antennae (close up in photo 2). I personally find such structures a miracle of natural engineering.

Turning to my copy of the superb Moths by (the recently deceased) Michael Majerus (The New Naturalist Library), one thing I learn about the Oak Beauty is that it has a melanic form that occurs in Holland but not in Britain.

For those unfamiliar with melanism: Much as people can differ in their eye colour and yet all remain members of the same species (human'), so some moth species can show considerable variation in their wing pattern. Within one species, some individuals might have patterned wings whilst others might have, say, matt black wings. Careful studies over decades have shown that the places where moths with certain wing patterns predominate are those places where having e.g. black wings is a recipe for good camouflage from predators (say, birds).

The increased prevalence of black winged moths of the Oak Beauty's sister species, the Peppered Moth (Biston betularia), in heavily polluted areas is an extremely famous example of supposed evolution in action (a.k.a. 'survival of the fittest') and consequently has drawn a very great deal of study and heated debate. From everything and anything convincing I've ever read however, the basic conclusion I've drawn is: it's a fact! You'll find no better, more balanced account than Michael Majerus' book above.

Finally, I can't help but end with a comment on the truly wonderful 'folk law' names of moths. The Oak Beauty, The Burnished Brass, The Twin Spot Quaker, Mother Shipton...- the list goes on an on. I commend the following link to one of my all time favourite poems: All These I have Learnt, by Robert Byron.

Song Thrush Turdus philomelus

I am an amateur naturalist trying to discover something about everything alive in my garden.

Photo 1 shows a photo of what is, I think, my favourite garden bird, the Song Thrush (Turdus philomelus), snapped on a snowy day in February.

In case you're wondering about the piece of wood lined with seeds in the foreground incidentally, I can tell you it is the latest in the small arsenal of apparatus I'm acquiring to catalogue my garden's natural history. Ladies and gentlemen I present to you...(drum roll)...The Walloon IR-Beam-Breaker!

Photo 2 explains: Having often been frustrated at seeing a bird on my lawn that I've been too slow or too far away to photograph well, and having a modicum of electronics knowledge, I've recently cobbled together a system for automatically capturing photos. With the cable in photo 2 plugged into my camera, anything crossing the line between the two margarine tubs interrupts an invisible, (harmless) infrared beam and sets off the camera's shutter. Though its rightful place might be my dedicated robin posting, you can see a robin in photo 3 kindly demonstrating the correct technique.

Anyway, back to the star of today's posting. What I've leaned about the Song Thrush (Turdus philomelus), has mostly come from the pages of Eric Simms British Thrushes (New Naturalist Series).

Thrushes are a large, globally distributed genus that includes the blackbird, the American Robin and the Ring Ouzel (an occasional visitor to the UK and perhaps the bird I'd most like to see incidentally).

Song Thrushes average about 32cm long and 74gm. The feathers on their back are a warm brown and they have a creamy-white, speckled breast. (The superficially similar Mistle Thrush (Turdus viscivorus) is about 4cm longer and has a whiter breast). Song Thrushes have a characteristic direct flight, easier seen than described (Mr Simms quotes speeds of around 48kph).

Song Thrushes breed from early March through to July and moult in July. UK birds typically do not migrate any great distance, though birds that do, do so around October.

Song Thrushes have a lovely piping voice (you can hear a clip on the RSPB site). Their repertoire can include imitations of other birds and supposedly even car alarms and the trilling of mobile phones. Singing peaks around April/May, when birds are most active in breeding and defending territories. One physiological trigger for singing is temperature: Mr Simms describes his own careful observations on how singing in his garden thrushes correlated with ambient temperature and also mentions that some researchers have induced premature singing in thrushes in winter by artificially raising the temperature.

In a study of territorial behaviour in Oxford, male/female pairs of Song Thrushes were observed to hold territories of around 150feet square during the breeding season. During winter, most territories were held by solitary males, though occasionally one would be held by a solitary females. (No doubt there's enough ecological complexity underlying this behaviour to motivate a whole PhD's-worth of research, if indeed such a study hasn't already been done).

It's not uncommon on a country walk here in the UK (does this happen elsewhere?) to hear the 'tap tap' of a Song Thrush engaged in the business of removing the shell of a snail by smashing it against a rock ('a thrush's anvil'). You can find some video footage on the RSPB site. Interestingly, Mr Simms says that snails tend to be a last resort food for Thrushes - their preference being worms, insects and berries (including those of Holly, Ivy, Yew, Honeysuckle and Hawthorn). Something I had not hitherto known was that Song Thrushes will forage on shorelines where they've been recorded feeding on periwinkles, dogwhelks and sandhoppers.

I'll close with a personal comment: For me much of the fascination and enjoyment of natural history comes from trying to acquire a smattering of 'scientific' understanding about my garden's life. At the same time of course, like everyone, I have an emotional response to the things I see. Actually however, in the case of garden birds, although I find them wonderfully formed and love to hear their singing, I personally don't find them 'cute' or 'charming' in the way I think some people do. I've heard the idea that birds evolved from dinosaurs ("dinosaurs that grew feathers"). The scientific truth of this is hotly disputed and I don't know enough of the debate to knowledgeably comment, but watching blackbirds scurrying around on my lawn, for me there is more than a passing resemblance to a hunting pack of miniature Velociraptors! No one's said it better than English poet Ted Hughes in his poem Thrushes

Terrifying are the attent sleek thrushes on the lawn,
More coiled steel than living - a poised
Dark deadly eye, those delicate legs
Triggered to stirrings beyond sense - with a start, a bounce,
a stab
Overtake the instant and drag out some writhing thing.
No indolent procrastinations and no yawning states,
No sighs or head-scratchings. Nothing but bounce and stab
And a ravening second.

Haematoccus algae

I am an amateur naturalist trying to learn a little about everything living in my garden.

Recently, in the interests of finding some life-form with which to entertain the legions of avid readers of this blog (hem, hem), I decided to investigate what life might exist in a small pool of rainwater that had collected in the crevices of a sheet of polythene lying in my garden. Putting a drop under my hobbyist's microscope I was immediately confronted by large numbers of the creature seen in photo 1 (scale:1 small division = 1um). Some were motionless. More excitingly, others were highly active, 'zooming' through the water at a rate of knots (see later)

Some internet searching later, and with the help of photo's such as those on Ralf Wagner's microscopy site, and I'm tolerably confident I'm looking at a Heamatoccus alga.

The red colouration, motile behaviour and the presence of the transparent, gelatinous envelope surrounding the central green body all fit with the the species being H. pluvialis on this site ('Algaebase') . I don't claim any certainty over this identification however, since firstly I'm no expert, and secondly the same site lists 5 other species in the Haematoccus genus and a staggering 123,336 species of algae overall.

The family Haematoccae is part of the Volvocales order of algae, one example of which - Volvox - is a perennial favourite with microscopists. The Volvocales are equipped with two whip-like flagella - the secret to their ability to 'swim' through the water. The length and positioning of any flagella on an alga is an important aid to identification. Unfortunately the quality of my camera/microscope optics doesn't appear to be good enough to have caught these in the (dormant) Haematoccus specimen in photo 1 (or is it that flagella are lost in the dormant state?) - but the superb photo's by Wim van Egmond here show them clearly.

In researching the life in my garden I constantly come across what I imagine at first to be 'obscure' creatures. "Beyond naming it, surely no-one can have found the time to learn anything interesting or remarkable about this little critter!" I think to myself. It's a constant source of enjoyment to me to learn I'm wrong, and that for just about anything I come across, someone somewhere will have discovered some remarkable or interesting 'story' (which isn't to say that vast amounts don't remain unknown about the natural world of course).

So it was with H. pluvialis. Beyond a few dry descriptions in an obscure journal, surely there would be nothing say? Wrong again! It turns out H.pluvialis is an algae of significant commercial importance. It produces the highest known concentrations of astaxanthin of any living creature and is cultured on a commercial scale. Astaxanthins are chemicals used in the cosmetics, food and feed industries. They are antioxidants and have been studied for their potentially beneficial effects against everything from cataracts to colonic cancer. Guerin et.al. have produced a review (Trends in Biotechnology, 21(5), 2003). Astaxanthins are cartotinoid chemicals responsible for the red coloration in photo 1. They act as a 'sun block' against harmful UV rays. Those dormant algae I observed in my microscope sample seemed to contain more red pigment than mobile ones. I assume this is because dormancy is, in part, a mechanism to survive in dry conditions when cells can expect to need more protection from the sun.

Algae introducing astaxathanins into the food chain is the reason why animals higher up like shrimps, salmon and flamingos end up with pink flesh or feathers.

Returning to the issue of the mobility of H.pluvialis, Burchardt et.al (Biodiv. Res. Conserv. 1-2, 163-166, 2006) give a figure for their swimming speed of 200m/h. Given that their size is about 20um, scaling this up, and assuming a human about ~2m tall and I've got my maths right, this corresponds to a person swimming along at 20,000 km/h!

Finally, I can't end without mentioning one of the few books I have that gives a fairly detailed introductory guide to freshwater algae, namely Freshwater Microscopy by W.J. Garnett. Though it contains no real information about Haematoccus beyond a mention, it covers many common UK species in some detail. First published in 1953, I particularly like dipping into it for its evocation of a seemingly quieter more 'holistic' (for want of a better word) world, before out-of-town shopping centres and a life of frenzied commuting up-and-down packed motorways, when armies of amateur hobbyists seemed to spend their evenings and weekends learning the art of painting watercolour landscapes, investigating the geology of their county, or studying the lifeforms in their village pond. Or perhaps that's rose-tinted nonsense, though I do wonder how many hobbyists there are today, who, of a typical weekend, boil hay in rainwater in order to culture pond protozoa for study as Mr Garnet advises!

On the other hand I may be entirely wrong and there are legions of you hay-boilers out there! If you're one such, do leave a message to say hello.

Common Pheasant Phasianus colchicus

I am an amateur naturalist trying to discover everything living in my garden.

Handsome fellow isn't he! Photo 1 shows one of two male Common Pheasants (Phasianus colchicus) that visited my garden recently. Living as I do in rural Oxfordshire, meeting one isn't unusual; their rearing and shooting is common hereabouts.

The RSPB estimates there are 1.8million breeding female pheasants in the UK.

From a search of the internet a few random facts I've turned up about pheasants include some evidence that pheasants are sensitive to noises beyond the range of human hearing (Stewart, The Ohio Journal of Science. v55 n2 (March, 1955), 122-125). Secondly, given a choice, the 'stuff' (sand, loam, straw, feathers...) in which an adult pheasant will choose to take a dustbath can be predicted ahead of time by noting the material a bird prefers to peck at when still a chick (Vestergaard&Bildsoe, B Acta Vet. Brno, 1999,68, p141). This may seem an esoteric piece of knowledge, but as anyone who has ever watched a documentary about battery chickens will know, feather plucking is a damaging problem among livestock birds under confined conditions and an understanding of pecking behavior in birds can have worthwhile commercial implications.

The Common Pheasant is native to Asia. Like the peacocks, the Common Pheasant is an example of a sexually dimorphic species - a species in which males and females show consistent difference in form. Male pheasants are brightly coloured; Females are cryptically camouflaged. Photo 2 shows a female I spotted lurking in my garden shrubbery early last summer.

Sexual dimorphism is a much studied topic in the theory of evolution. Scientists would like to understand more deeply what forces encourage it and what advantages follow.

An internet search led me to a number of papers on sexual dimorphism in pheasants but unfortunately most were on the pay-to-view sites of commercial publishing firms. This always irritates me as it's typically you and I, the taxpayer, that has paid for the research contained in these papers. To be asked to pay again to read the results seems a bit much! Anyway, I did manage to find a few freely available papers from which I learn that female pheasants choose male mates based, in part, on the length of their spurs. Studies have shown spur length to be an honest indicator (see my peacock posting) of male health - males with longer spurs really do seem to be fitter than less well endowed males.

Spurs are a secondary sexual characteristic - a characteristic that differs between the sexes.

Girl pheasants also appear to judge their men folk according to the quality of their wattles (the red cheek patches in photo 1). Smith et.al. provide one study of this. My (amateur) understanding of their work is as follows:

Biologists had previously worked out that certain 'carotinoid' chemicals were associated with coloured appendages in some animals. At the same time, animals getting a good diet were known (perhaps unsurprisingly!) to have stronger immune systems than poorly nourished specimens. Smith et.al. wondered whether carotinoids were the root cause of both i.e. whether both the strength of a male's disease immunity and their wattle quality were directly controlled by the amount of carotinoids in their diet. If so, this might provide a very natural explanation of why females have 'a thing' for wattles -good wattles would be an honest indicator of the disease resistance of a suitor.

And the answer...after a series of detailed experiments Smith et.al. found no such correlation! Back to the drawing board in terms of discovering the deeper explanation of what's going on, but a nice example for those who might question whether science isn't ultimately a process of rigorous enquiry.

A lichen Aspicilia calcarea

I am an amatuer naturalist trying to discover what lives in my garden.

Those following my recent posts will know I have been on something of a mission to blog the lichen-life on the exterior of my house. Photo 1 shows yet another inhabitant - another crustose lichen (for those unfamilar with lichens, see my post here).

Incidentally, photo 1 also captures (upper left) our old friend, the moss, Tortula muralis.

After a little research I'm confident the lichen here is Aspicilia calcarea. Characteristic features include the cracked, white thallus (the main body of the lichen) and the irregularly shaped apothecia (the black, spore-liberating cups) sunk into the thallus. The books tell me that A. calcarea is common on hard calcareous walls etc. in lowland Britain. Photo 2 shows a closeup.

For those wanting a cheap photographic key to some common, British, urban lichens incidentally, I recommend the short-form guide sold by the good people of the Field Studies Council . For something more detailed the book Lichens (Frank S.Dobson) is especially good.

I'm fond of lichens. Their ability to shrug off the worst the elements can throw at them gives them, for me, an appealing minature 'feistiness' - I picture them squatting on exposed boulders on windswept mountain sides goading the rain "Come on! Give me your best shot! Is that all you've got pal !?"

On a more rational note (!), something that intrigues me is the diverse array of colours and shapes lichens adopt. I have no deep expertise in evolutionary ecology but as I understand it, there is nothing haphazard about the forms taken by species. Life is hard and an ever-present scarcity of resources and the threat of predation and disease is a constant imperative, forcing species to individually specialise in unique methods of suvival. A famous example is of course the beaks of finches, with different species having been driven to evolve different beak-shapes to allow them to eat different nuts and seeds. Different birds evolving different beaks to help them occupy different feeding niches is one thing. The distinct environmental pressures or purposes that drive two lichens such as A. calcerea and C. citrina to adopt such different colours and (once you look closely) really quite different textural forms, when both seemingly occupy the same ecological niche of lowland stone (indeed, the same household windowsill in my case!) - I struggle to guess. Do leave a comment if you can help me.

European Hornet Vespa crabo

I am an amateur naturalist trying to learn something about everything alive in my garden.

Photo 1 (click to enlarge) shows the handsome insect I found lying dead on a windowsill in my house some months ago. I am not expert at insect identification so at first I wasn't sure what I was looking at, but a little internet browsing and I'm confident I've found a European Hornet (Vespa Crabo): of the half dozen-or-so social wasps one might encounter in a British garden, the hornet is the only one with a distinctly brown coloured thorax. Much the most extensive introductory source I've come across online is Dieter Kosmeier's excellent hornet website.

Despite their fearsome reputation hornets are no more likely to attack humans than other wasps, nor is their sting notably worse. They are voracious predators of other insects however; a nest colony can take up to half-a-kilo a day. There are even records of hornets taking down pairs of copulating dragon flies (see Dijkstra et. al., Int. J. of Odonatol. 4(1),17-21, 2001).

Queen hornets hibernate over winter - the site of the Bees, Ants and Wasps Recording Society gives a record of a queen discovered beneath a rotting branch of cherry wood. She emerges around May and begins the process of constructing a nest and egg laying. By mid summer the nest is in full swing and may contain in excess of 500 individuals. Nests of one species of hornet (Vespa wilemani) have been recorded at altitudes of 2300m (Martin, Jpn.J.Ent.61(4), 679-682,1993). Come winter the nest is permanently abandoned (hornets do not reuse a nest the next year).

Figure 2 (click to further enlarge - if you dare!) shows a close up of my hornet's feasome jaws and, atop the head, the circle of small primitive light sentive 'eyes' (ocelli). Counting the number of segments on the antennae (=12) tells me my hornet is a female (males have 13)

A debate amongst professional naturalists concerns the mechanism and role of 'brood policing' in Vespa crabo. In brief the debate surrounds the question of why only the eggs of the queen, and not of the workers, are allowed to hatch (I was surprised to learn that the workers are not in fact sterile, and are quite capable of producing progeny). In the 60's the British evolutionary theorist W.Hamilton, argued mathematically that, other things being equal, in order to benefit their gene-line organisms ought to behave in ways that favour their close relatives (kin). Genetically however, a Vespa crabo worker is closer to its own offspring or indeed the offspring of a fellow worker than that of the queen. Despite this, workers ruthlessly seek out the eggs of fellow workers and discard them. Foster et.al. argue (Molecular Ecology (2000) 9, 735-742) that this may be due to the queen chemically controlling the 'minds' of the workers, hence the title of their paper 'Do hornets have zombie workers?' - although overall the jury seems still out.

Or at least that's my loose understanding of things. As I say often, I'm not a professional. I'm happy to be corrected and in particular I've not managed to follow the quantitative aspects of this debate. For example, Foster et. al. begin:

"In a colony headed by a singly mated queen, workers should prefer rearing sons (r= 0.5) and other workers’ sons (r= 0.375) to their mother’s sons(r= 0.25)'

I get the general idea, but can anyone give me a simple explanation of what these numbers mean and how they're calculated?