A Buzz in the Meadow (20 page)

I had no more cause to think about yellow rattle until some years later, when I was investigating the declines of many UK bumblebee species. It had become clear that most of the bee species that had declined severely were the longer-tongued species and those that tended to emerge late from hibernation; species such as the great yellow, shrill carder, ruderal and short-haired bumblebees. When I began studying bumblebees in earnest I had seen none of these species and was desperately excited at the prospect. It also became clear that little was known about these bees. Searching the scientific literature revealed hundreds of studies of buff-tailed bumblebees and other common species, but almost nothing had been written about the rarer bees. I was determined to put this right – after all, we could not hope to conserve these creatures if we did not know anything about them.

By the time my interests in bumblebee conservation really came to the fore I had moved from Oxford to Southampton University, and I travelled far and wide in the UK to track down these exotic-sounding creatures. I saw my first brown-banded carder at Dungeness in Kent; red-shanked carders and ruderal bumblebees on Salisbury Plain; shrill carders on the Somerset Levels; and great yellows on South Uist. I went abroad, to Russia, Poland, Switzerland and even New Zealand, to find healthy populations of the rare species. Together with my students, I amassed data on the food plants used by all the different species that we saw, both common and rare, eventually accruing tens of thousands of records. We wanted to know how the various bee species differed with regard to the flowers they preferred, and whether the rare bumblebees were dependent on particular, rare flowers. In all this work, some clear patterns emerged. The sites that supported lots of bumblebee species, and those where the rare bumblebees were to be found, all tended to be flower-rich grasslands. There was usually a lot of red clover, which long-tongued bees favour as a source of pollen, and often there was yellow rattle.

While the queens of our common bumblebee species emerge early in the spring, sometimes as early as February, the queens of our rare species tend to emerge much later. Shrill carders and great yellows are not seen much before June, having slept since the previous September. This may be in part because the flower-rich grasslands they inhabit actually have few flowers in spring, despite their name. Grassland flowers tend to blossom from late May onwards, so it makes little sense for the bees that live there to wake up any earlier; if they did, they would starve. Yellow rattle is one of the first grassland flowers to bloom, and its deep flowers provide vital nectar and pollen for the hungry queens coming out of hibernation. It thus makes sense that the places where these bumblebees thrive tend to have good strands of yellow rattle.

It turns out that there is much more to the relationship between bumblebees and rattle than this. Since I was taught plant identification by Andrew Lack all those years ago, plant taxonomists have moved yellow rattle from the Scrophulariaceae to the no-more-pronounceable Orobanchaceae.
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The common name of this family is the broomrapes, and therein lies the clue to their unusual biology. Some members of the broomrape family are parasites on other plants, particularly legumes such as beans and broom. They don't bother producing green chlorophyll to photosynthesise, but instead send out long roots that latch on to the roots of other plants and drain their nutrients. The bulk of the plant is below ground, for it has no need of sunlight, but in spring each plant sends up a yellow, sickly-looking flower spike which, despite its anaemic appearance, is quite attractive to bees. Broomrapes are rare in Britain, but they are common in more southerly parts of Europe and can even be a pest of broad-bean crops in the south of Spain. Yellow rattle is a cousin of the broomrapes, and although it has green leaves and photosynthesises like a normal plant, it does share some of their parasitic habits. The roots of rattle latch on to those of nearby grasses, drawing out sugary sap. Patches of rattle within a meadow are often conspicuous, for the surrounding grasses are stunted and yellowed, weakened by the parasitism – reminiscent of vampire victims that are being slowly drained of life.

Scientists at the UK's Centre for Ecology and Hydrology in Wallingford have explored whether rattle might not be a powerful tool in the conservationist's armoury. The recent realisation that we have destroyed most of Europe's flower-rich grasslands has led to efforts to restore damaged meadows, or even to create them from scratch, as I have been doing at Chez Nauche. However, the great enemy of such projects is high soil fertility. Beautiful, diverse grassland that took centuries to develop can be reduced to a green sward of grass with barely a flower in sight within just a year or two, by the single act of adding chemical fertiliser. Ancient grasslands tend to have low soil fertility, so grasses grow slowly and there is lots of room for other plants. In these conditions plants that are able to extract nitrogen from the air are at a huge advantage, and so legumes tend to thrive, for they have root nodules containing nitrogen-fixing bacteria. Hence flower-rich grasslands are rich with trefoil, vetches, meddicks, restharrows and clovers – all legumes. This is also good news for bees, since they love the pollen and nectar of legumes. Chuck on a sack of fertiliser and the grasses sprout up like crazy and smother everything else.

Once fertiliser has been added to a meadow, it is exceedingly difficult to remove it. The fertility will slowly decline if no more fertilisers are added and if a hay crop is removed every year, but this can take decades. By attacking grasses and reducing their ability to dominate the sward, yellow rattle offers the possibility of speeding up the process. To test this idea, Richard Pywell and his colleagues at the Centre for Ecology and Hydrology set up an experiment at Little Wittenham Nature Reserve in Oxfordshire, a cluster of pretty, steep-sided chalky hummocks just south of the River Thames. By coincidence, I used to go sledging there in winter when I was a PhD student at Oxford. Pywell sowed patches of species-poor, ‘improved' grassland with yellow rattle seeds, after first scarifying the surface to provide some bare ground. The rattle established well, and quickly began to suppress the grasses. After two years he sowed a mix of wild-flower seed into the experimental plots, and then monitored whether they established successfully. The results were quite clear: the wild-flower seed mix took much better in plots with lots of rattle, presumably because there was less competition from the grasses.

It seemed to me that my meadow provided an opportunity to follow this up, and to simultaneously boost its floral diversity. Rattle has many hemiparasitic relatives; there are other species of rattle, such as greater yellow rattle and narrow-leaved rattle, and also eyebright, red bartsia, meadow cow-wheat, and so on. These other species might also prove effective at suppressing grasses and boosting floral diversity; perhaps some might even be better than yellow rattle? So in September 2010 I returned to Chez Nauche with a group of volunteers, my PhD students Andreia Penado and Leanne Casey, and two staff from the Bumblebee Conservation Trust, Pippa Rayner and Tasha Rolph. At the time I had a very old Yardman sit-on mower, and I set about mowing 120 ten-by-ten-metre plots; the mowing was needed to get rid of the vegetation that had sprung back since the July hay cut, and to provide some bare ground for the seeds to germinate in. Unfortunately my Yardman expired after just a handful of plots, and I have never managed to coax it back into life since. Not having the funds to replace it with a new one, I rushed out and bought a normal lawnmower, and spent the next six days mowing neat squares into the field. The team of four girls followed behind me, sprinkling in seeds and performing a strange, collective shuffling dance to bed the seeds in (Pywell's team used a tractor-mounted roller, a far more sensible approach).

It was not long before my farming neighbour, Monsieur Fontaneau, happened to drive along the track adjoining the meadow, with the larger of his two sons in the passenger seat. He stopped, and they stared for a while. They turned their engine off and wound down the window. I waved, and he waved back. They stayed for perhaps ten minutes, before they drove away.

Half an hour later another car came along the track; it doesn't go anywhere, petering out just a kilometre beyond the meadow, so they were unlikely to be random passers-by. They too stopped and watched for a while, and then reversed away. Over the next few days perhaps a dozen different cars came by, roughly a dozen more than would normally pass the meadow. Clearly word had got out that the Englishman was up to something strange. I think I recognised the sturdy lady who had nearly shot me seven years earlier. Monsieur Fontaneau came back with his thin son. They all stopped and watched for a while, though none ever came over to ask what we were doing, and I didn't attempt to approach them with an explanation, which I felt sure I would be unable to provide in my hopeless French. To this day I wonder what they thought we were doing, mowing endless neat squares in a vast field, then performing strange, ritual dances in them.

I've been back to Chez Nauche every spring since to survey the plots, counting and identifying every plant species present. It takes several days, and is repetitive but rewarding work. Identifying some of the grasses is a particular headache, but I enjoy the challenge. The character of the meadow changes from year to year, depending on spring rainfall and temperature. Sometimes it is like a jungle, with the taller plants reaching head-height, while in drier years it is much sparser with patches of bare soil. Every year we find new plant species that I have not seen before. The yellow rattle has certainly established itself, though it is very patchy, and there is also some greater yellow rattle and small scatterings of the other species. Clovers seem to be spreading rapidly in many of the plots, so that they are thick with bees. Shrill carder queens, which love red clover, have become common in late May.

It is too early to say yet whether the different hemiparasites are having any effect. I have long since forgotten which plot is which (although of course I have this written down and filed away) – a good thing because otherwise I might subconsciously bias the results. In a year or two I will analyse them and see what it shows. Whether the experiment produces positive results or not, it is clear that the meadow as a whole is slowly improving, with a few more flowers every year. I do not know whether it will ever reach the dizzy heights of floristic diversity found in an ancient hay meadow, but it seems to be turning into a fair facsimile.

One of the few places in western Europe where there are still quite a few pristine flower-rich meadows is in the Alps. The sheer inaccessibility of many of the higher pastures has protected them to some extent from the ravages of modern agriculture, and the Alps remain the largest biodiversity ‘hotspot' in Europe. A visit to these high meadows in late spring or summer is a must for any nature-lover. The weather is hugely unpredictable, but if you are lucky and catch the Alps on a sunny day they are breathtaking. Lush carpets of flowers tumble over the rocky slopes, buzzing with insect life making the most of the short summer. Of course the backdrop of dizzying snow-capped peaks and deep valleys with glimpses of distant lakes sets everything off nicely, too. Because of this extraordinary beauty and diversity, the staff at the University of Stirling decided that Switzerland would be an ideal place for a summer field course for our biology students. Despite the high cost of living in Switzerland, it was surprisingly cheap to rent a huge chalet high in the mountains, presumably because many of these buildings lie empty through the summer, the bigger influx of tourists coming during the winter to ski. To my delight, when we arrived at the chalet for the first time in June 2009, the first plant I noticed was yellow rattle, growing around the edges of the rough lawn. It turned out to be common in the area, not so much in the very high meadows, which tend to be heavily grazed by cattle, but in the lower areas downhill from our chalet, where the fields are kept free of livestock in the summer to provide a hay crop.

We set the students to work on a range of projects, one of which I supervised, on the diet of Swiss bumblebees (no muesli or chocolate for them). The Alps have all sorts of bumblebee species, including almost all the British species and a whole heap more besides, and identifying them was initially a challenge. I was particularly excited to see great yellow bumblebees, in Britain a rarity largely confined to coastal grasslands of the Hebridean islands and seldom found more than a few metres above sea level, but here happily living a kilometre or two higher amongst the mountain peaks. Despite the lack of bilberries there were plentiful bilberry bumblebees, among the most colourful species, with huge red bottoms and yellow stripes. On our first morning we recorded sixteen different species within a short walk of the chalet.

Amongst these was a species I had seen only once before, in the mountains of southern Poland – a species with no English name,
Bombus wurflenii
. It is one of a very small number of bumblebee species that has become a specialist nectar-robber, a professional thief, which makes its living by cutting holes into the side or back of flowers and stealing their nectar. Because it does not enter flowers by the conventional route it does not contact the reproductive parts and so does not pick up or transfer pollen. If flowers could speak (or think), one might imagine them shouting, ‘Oi, stop! Thief!' Britain has species such as the buff-tailed and white-tailed bumblebees, which sometimes stoop to robbery if they are hungry and encounter a flower that is too deep for their short tongues – they are opportunistic thieves. In contrast
Bombus wurflenii
are incorrigible larcenists. They are well equipped for their profession. The mandibles of most bumblebee species are approximately smooth and paddle-shaped, well adapted for moulding wax and feeding broods. Buff-tailed and white-tailed bumblebees have small teeth on the edges of their mandibles, which help them to bite through the back of flowers when the need arises, but it takes them a little while to do so. In contrast the mandibles of
wurflenii
are armed with a row of long, curved and sharply pointed teeth, which enable it to slice though the sepals of most flowers in moments.