Friday 29 November 2013

A Tale of Two Willow Wrens

Like Dickens' novel, A Tale of Two Cities, this story is also one of contrasts; between birds, places and ways of studying natural history. It was another English literary giant, the 18th century natural historian Gilbert White - and grandfather of biological recording - who first distinguished, on the basis of their songs, not two but three distinct warblers amongst a group previously thought of as a single species - the Willow Wren; these were Chiffchaff, Willow Warbler and Wood Warbler.[1]

Since Gilbert White first separated the three species, Wood Warlber has probably declined to a much greater extent than the other two. It now has a westerly distribution in the UK and an encounter with Wood Warbler is a red-letter day for most naturalists. Despite the early confusion they are reasonably easily identified by sight, being larger, brighter and yellower than both Chiffchaff and Willow Warbler. I have rarely seen Wood Warbler at home in Lancashire, although this year I was astonished to find a pair in a local woodland which subsequently bred. (Another local naturalist found a second breeding pair - a wonderful turn of events that we hope will be repeated in future years.)

The jokey epithet of Wiffwaff is given by birders to a warlber which could be either Chiffchaff or Willow Warbler and is testament to the fact that these two species are very similar in appearance and still cause confusion from time to time. There are quite reliable differences, but if a good enough view isn't forthcoming, they are difficult to tell apart by sight. Fortunately there is one excellent way to distinguish them - their songs which, although equally delightful, are quite distinct and easily identified, as Gilbert White first noted. (The beautiful song of the Wood Warbler is also very characteristic.)

The Swallow and the Cuckoo may be the iconic harbingers of the British summer, but it's the migrant warblers that lend so much rich texture to our springtime soundscape. In March I anticipate their arrival with child-like excitement. Chiffchaffs, Willow Warblers, Blackcaps, Whitehroats, Garden Warblers - each arrives from Africa singing songs not heard for six months or more, dispensing joy freely to anyone who cares to listen.

Weekly totals of my Chiffchaff records for 2011-2013.
In 2010 I started making biological records using a GPS datalogger with a voice recording facility (effectively a GPS-enabled dictaphone).[5] It meant that I could make a record of a bird in as much time as it took me to press a button and say "Willow Warbler!". Like most biological recorders, I'm somewhat eccentric about what I record and when I started carrying this device about with me, I found it hard to let any encounter with a summer migrant pass without making a record. Of course the odd one slips by now and again - it's awkward to interrupt a meeting at work to make a record of a singing Chiffchaff - but I get a good proportion of them.

One consequence of all this recording is that I can look back and see a more or less complete picture of my personal encounters with these birds over the course of the summer. The incredibly cold March of 2013 delayed the arrival of many  summer migrants; an event comprehensively documented by records submitted to the BTO by thousands of recorders up and down the country.[2] But there's something about seeing that same phenomenon reflected in your own personal observations that really brings it home.

In February 2013 I started working for the Field Studies Council at Preston Montford in Shropshire (just north-west of Shrewsbury), although I continue to live in Horwich, Lancashire and split my time fairly evenly between the two.Whereas in 2011 and 2012 most of my summer migrant records were made in Lancashire, in 2013 I made good numbers in both counties. In Lancashire, most of my summer migrant records are made when I walk with my dog through countryside on the edge of the West Pennine Moors. In Shropshire, most of them are made around the field centre where I work and at a nearby site where I frequently camp (both adjacent to the River Severn).
Weekly totals of my Willow Warbler and Chiffchaff records for Preston Montford, Shropshire in 2013.
 (Chiffchaff photo thanks to Lip Kee.)

Chiffchaff and Willow Warbler frequently occur together and both are ground-nesters favouring open habitats with scrub and scattered trees. Chiffchaff tend to prefer, or tolerate, more mature stands of trees than Willow Warbler, but there is considerable overlap. The countryside differs between the two places where I recorded these birds in 2013, with that in Lancashire being more upland in character, but each of them offers plenty of suitable habitat, on the face of it, for both Willow Warbler and Chiffchaff.
Weekly totals of my Willow Warbler and Chiffchaff records for Horwich, Lancashire in 2013.  
(Willow Warbler photo thanks to Andreas Trepte, www.photo-natur.de.)


Given the apparent suitability of the habitat in both places, the pattern of my encounters with Willow Warbler and Chiffchaff in each show striking differences. Although I recorded Willow Warblers in Shropshire as they arrived, these moved on quickly. In Lancashire I heard them in good numbers, just as in previous years, and it was easy to count 10 or more birds during a walk of an hour or two. In Shropshire I only made 8 Willow Warbler records over the entire summer - and all of those, I believe, were passing through. Although I recorded more Chiffchaffs in Shropshire than in Lancashire, I had good numbers in both counties.

I remember a visit to the headquarters of the BTO in Norfolk in 2012 and recall how staff bemoaned the scarcity of Willow Warbler there, getting quite excited when one was heard on the adjacent reserve! To be honest I didn't think much of it because in Lancashire I had just as many Willow Warblers as ever. But, at that time, the BTO researchers were seeing the preliminary results of Bird Atlas 2007-11- a project collating the observations of over 40,000 volunteers (of which I was one!) - and they saw a bigger picture emerging of a massive decline of Willow Warblers in the south of England.[3][4]

Willow Warbler change (with permission of BTO)



Still it rocked me when I saw that decline for myself as I compared Shropshire and Lancashire this summer. Part of it was because I hadn't imagined that the loss would have been as dramatically clear as far north as Shropshire, but there's no doubt that the impact on me was greater because I witnessed the difference through my own observations.

We don't yet know the reasons for the decline of Willow Warblers in the south of the country compared to the north - in fact it is a pattern that the new atlas shows is reflected by several other woodland and farmland birds. Climate change may be playing a part - either in the summer or wintering quarters - as may other anthropogenic factors, but at the moment we are speculating.

I wonder what Gilbert White would have made of it all? As a great advocate of learning through direct observation he would have approved of my efforts and he would surely have been astonished at the power of the massive collaborative effort for the BTO's Atlas project. But what of the decline of the Willow Warbler and the possible causes of it? Perhaps he would, like many of us, have felt simultaneously excited and depressed.

Dickens' words, penned between White's time and our own, seem particularly apt: "It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness". We have to hope that our ingenuity in tracking changes in the natural world around us does not end up merely as a means of documenting our own foolishness. And if you are lucky enough to live in a part of the country where you can still hear Willow Warblers singing in the summer, then enjoy them; a summer may soon come when they are no more than a memory to your part of the world.


1 See a short biography of Gilbert White here:http://www.nhm.ac.uk/nature-online/science-of-natural-history/biographies/gilbert-white/ [back]
2 A news item from the BTO's Birdtrack project documenting the slow start to the Spring of 2013:http://www.bto.org/volunteer-surveys/birdtrack/news-archive/2013-03/slow-start-spring [back]
3 A preview of the Willow Warbler's story from the BTO Atlas 2007-11: http://www.bto.org/about-birds/bird-of-month/willow-warbler [back]
4 The BTO Atlas 2007-11: http://www.bto.org/shop/bird-atlas [back]
5 The Gilbert 21 project: http://www.gilbert21.org.uk/ [back]



Friday 1 November 2013

Sandhill Rustic Dreaming

A singing robin once stirred me from a garden reverie on a gentle September afternoon. Its song, imbued with autumn melancholy, seemed to express both mortality and living beauty. I looked up at the singer, back-lit by late afternoon sunshine filtering through the elder where it perched. A light rain fell, bending, scattering and amplifying the light around the bird. For a few sublime seconds I lost all sense of myself. There was the exquisite scene before me, but no me; no past and no future. It was profoundly peaceful.

A perfect moment in time – that’s how I think of it – a glimpse of Gillespie Magee’s and Basho’s face of God[1]. I’ve known a handful of moments like this and they’ve all taken form during solitary contemplation of nature. I cannot lose myself in company; with other people I’m always aware of my reflection, or perhaps my shadow. Other people have brought me moments of greater happiness – for example when my children were born – but none can bring me the peace that nature sometimes does.
On a warm mid-August evening in 2008 I sat alone in the low fore-dunes of Lancashire’s Sefton Coast waiting for the sun to go down. I was keeping an appointment with a rare and beautiful creature that is as much a part of this coast as the dunes it was named for. A year before I had contributed to the discovery a colony of the sandhill rustic moth here, four years after it was last seen on the Sefton Coast[2]. It was feared extinct in Lancashire but the elusive beastie had only moved a few kilometres up the coast, its changing distribution mirroring the dynamic embryo dunes it dances around.

Now I was embarking on a two-week study for a Masters degree during which I would spend, weather permitting, every night searching for sandhill rustics along a four kilometre stretch coast running from Ainsdale to Southport and collecting data that I hoped would illuminate the their relationship with this magical shifting place. I had planned it for a year and it had consumed my thoughts. Every sandhill rustic I found would become a precious line in my spreadsheet, another hard-won point on my graphs.

I had tried to imagine every conceivable way in which it might pan out and account for everything that could go wrong. But adult sandhill rustics are only abroad for a few weeks in late summer, spending the rest of the year as eggs, caterpillars and pupae amongst the roots of the grasses on which they feed under the low embryo dunes, and I had just a fortnight’s annual leave to do my fieldwork. I knew that a week or so of cold, wet nights would blow my carefully laid plans out into Liverpool Bay like so much sand.

And yet, as I sat and watched the sun set, an extraordinary calm settled on me. Right then, there was nowhere in the world I would rather be, nothing I would rather be doing and, for once, no-one’s company I wanted for. I sank my hand into the warm sand and lifted it, letting the grains spill between my fingers, wondering, as I watched them catch the light summer breeze, if there were more grains of sand on all the beaches on the earth than there were stars in the universe. For a few precious seconds I lost myself to another perfect moment in time and so began my sandhill rustic dreaming.
The Dreamtime of the Australian Aborigines is a multi-layered world view embodying systems of belief, ritual, land stewardship, social relationships and much more. It would be a difficult thing for someone like me - a product of western culture - to understand even if I had access to an encyclopaedia of information on it, but the Dreamtime is maintained by closely guarded oral and ritual traditions; outsiders only catch glimpses of its incredible richness. The traveler and author Bruce Chatwin saw more than most, giving fascinating insights in his book Songlines. I first read Songlines over 20 years ago when I was in my late twenties and it left an indelible impression on me; it coloured the way I see the world.

The songlines are held to be the original routes of ancestral creatures who sang the world into being as they walked the land of the Dreamtime. They form a network covering Australia, connecting key features of the landscape and sacred sites (often one and the same). Landscape, animals, plants and people are all inhabited with Dreamtime spirits and the songlines are both routes and stories which are periodically re-walked and and re-told to bring them alive, allowing them to exist. Every time a songline is sung, the world and its spirits are created again.

In the oral tradition of the Aborigine Dreamtime, people are responsible for specific parts of songlines, each focused on the spirit of a different animal, plant or place. The spirits and songlines entrusted to a person are their dreamings. Someone may have a honey ant dreaming, another a eucalyptus dreaming, someone else a billabong dreaming and so on.

In the event, my two-week night-time odyssey on the Sefton Coast went largely to plan with just a single night lost to bad weather. On many nights I was on the beach from dusk to dawn and, perhaps inevitably, I fell in love with the place. During those two weeks in 2008, that stretch of sand belonged to me at night; it was my place. I came to recognise individual dunes by their silhouettes; different patches of sand couch and saltmarsh grass revealed their unique characters to me; I learned the most auspicious places to stop for a cup of tea or take a short nap; and of course I discovered the sites beloved of the sandhill rustic moth. For two weeks I strived to see as a sandhill rustic does, to think like a sandhill rustic does; I followed the songlines of the sandhill rustic and collected my data along the way.
As an academic endeavour it was a great success; the sandhill rustics gave up many lines of data to my spreadsheet which were, in turn, consumed by my GLMs and GIS[3] and transformed into colourful maps illustrating habitat suitability models for the moth. The examiners of my thesis[4] were suitably impressed and awarded it a favourable mark, which I suspect was largely based on the unfathomable statistics and the prettiness of the maps.

But for me the greatest legacy of the project is an abiding relationship with the sandhill rustic and its home on the Sefton Coast. It's a cliche, but it's true: the more you find out about any part of nature - even the tiniest part - the more, you realise, is unknown. In Britain the sandhill rustic is represented by three distinct and widely separated coastal sub-species and there's another one in Ireland and yet more on continental Europe where some sub-species favour dry inland areas. Each sub-species has exacting habitat requirements that are frequently very different from each other. How did their geographic isolation come about? Are these sub-species on the way to evolving into distinct species?

On the Sefton Coast, and along the coast of North Wales, the sandhill rustic is largely confined to low embryonic dunes dressed in sand couch (the main food-plant of the caterpillar) that are regularly inundated by the tide. These rare conditions are restricted to small areas and, probably as an adaptation to this scarcity, the sandhill rustic is less flighty than other moths: it would not pay to fly too frequently and risk losing touch with the only place for miles around where you and your con-specifics can survive. And yet, when a new patch of this dynamic habitat developed a couple of miles from the main colony on the Sefton Coast - with no suitable habitat in between - sandhill rustics found it within a few years and established a flourishing colony there. Did the adult moths fly there? Or did they perhaps travel there passively as larvae within the stems of their foodplant when it was uprooted and transported by winter storms? That is, after all, how the seeds of their foodplant must have arrived.

But is there even more to this relationship with the sea? Why do sandhill rustics favour areas where their foodplant is covered, from time to time, by high tides? Immersion may be important in some way, perhaps acting as a trigger that enables the short-lived adults to synchronise emergence from their subterranean chrysalises, giving themselves, and each other, the best chance of finding a mate. Certainly on some nights the proportion of freshly emerged adults (identified by their habit of holding their new inflated wings above their backs to dry) is staggeringly high compared to the average night, suggesting a synchronised emergence. But this idea has not been empirically tested.

Science doesn't yet have all the answers to these questions, but in my dreaming there are answers. My mind's eye looks down on Britain and, like a time-lapse satellite image spanning hundreds of millennia in minutes, ice ages come and go, sea levels rise and fall and the very shape of the country changes and shifts. Here and there, where the land meets the sea, dunes rise and fall, they expand and shrink, they migrate along the coastline, sometimes joining neighbouring dunes and sometimes splitting and separating. Similarly, over the millennia, dry grassy and heathy inland habitats come and go and move around the shape-shifting landscape. Superimposed over these places are the sandhill rustic populations - or rather their ancestors - here joining, there splitting and drifting apart as they follow their migrating habitats. Some populations separate for so long that they start to speciate - becoming distinct sub-species. As the current climate develops, woodland dominates inland and sandhill rustics only remain in populations around the coast where conditions are to their liking. The populations around the shores of Liverpool Bay and North Wales evolve an intimate relationship with the sea, using currents and storms for dispersal, ensuring that they keep pace with their dynamic and mobile habitat, and using the tides as a clock to synchronise their emergence and maximise breeding success.
Every year, towards the end of July, my thoughts return to the sandhill rustic and, pretty soon after that, my footsteps to the Sefton Coast. For a night or two each year I walk the sandhill rustic songline, finding and recording moths and keeping my dreaming alive. It's a sort of touchstone for me - one of those annual events that all naturalists use to recharge their spirits and, I believe, re-affirm their own identity. We all have our touchstones, our sacred sites, our dreamings.

Australian Aborigines inherit their dreamings - not directly from their mothers or fathers, but from a place. When an expectant mother first feels her baby move in her womb, the place where she is - and its associated dreamings - become the responsibility of her unborn child. We naturalists choose, or discover, our dreamings rather differently - our two traditions are, after all, worlds apart. I'm not trying to equate Aborigine dreamings and the passions of naturalists, but I do believe that there are interesting parallels. Not least a deep - often spiritual - connection to the landscape and the plants and animals that we share it with, a feeling of responsibility towards them and a sense that man is not above nature.

Some years before I discovered my sandhill rustic dreaming, I spent a few hours in the company of other ecologists on the Sefton Coast where a gifted teacher[5] inspired us by bringing the dynamic geomorpholgy of the dunes alive in our imaginations. "This place is made by Sand and Sea and Wind." He repeated it like a mantra - Sand and Sea and Wind. As he, and we, became more and more transported by his narrative, his words took on a kind of rhythmic quality - Sand and Sea and Wind. I think about it now as part of his songline - part of his dune geomorphology dreaming.

Many naturalists, I'm sure, would prefer to think of their 'taxonomic interests' rather than their 'dreamings' and, lets be honest, listing your dreamings rather than your taxonomic interests on your CV might not maximise your employment potential! But I've met many naturalists whose interest in nature is so passionate and so inseparable from their identity, that 'taxonomic interest' just doesn't seem to do cover it, so I often think of them as having their own dreamings. I've got friends an acquaintances with all sorts of dreamings - from the very general to the very specific - bird dreaming, Sphagnum dreaming, Berwyn Mountain dreaming, sand lizard dreaming, moth dreaming, hen harrier dreaming, snail dreaming, bat dreaming, bee & wasp dreaming, grass dreaming, Sefton Coast dreaming, fungi dreaming, flowering plant dreaming, hoverfly dreaming, river dreaming, conifer dreaming, cranefly dreaming, bramble dreaming...there are many more. I have other dreamings too - a spider dreaming and a meadow pipit dreaming, to name a couple.

Our dreamings take shape at the place where what we know meets what we imagine. We must hope that what we know and what we discover will provide us with the tools we need to address the unfolding environmental crisis, but it is the spiritual power of dreamings that can persuade a confused and prevaricating world that it is worth fighting to save the minutiae of nature and its myriad stories written on the landscape over millennia.


1 A haiku by Basho (1644-1694) reads: ‘How I long to see / Among dawn flowers / the face of God’. The poem ‘High Flight’ by the Spitfire pilot Gillespie Magee (1922-1941) ends: ‘And, while with silent, lifting mind I've trod / The high untrespassed sanctity of space / Put out my hand, and touched the face of God.’ [back]
2 Also instrumental in the discovery of the new colony were Graham Jones – a long-standing sandhill rustic enthusiast who had recorded the last moth seen on the coast in 2003 – and Sefton Coast Ranger Pete Gahan who found the very first sandhill rustic moth from the new colony in 2007. [back]
3 Generalised Linear Models and Geographic Information System. [back]
4 http://www.merseysidebiobank.org.uk/Literature/BurkmarThesisCompressed.pdf [back]
5 Paul Rooney, Liverpool Hope University. [back]