Underground influencers

By Athayde Tonhasca

“Everything is connected” is the sort of vacuous new-age twaddle churned out by the self-help industry. And yet, stuff and nonsense often holds a grain of truth. For example, we would have to look hard to find a connection between earthworms and pollinators. But such an association seems to exist, and it could be of consequence for pollination services.

Earthworms (mainly of the family Lumbricidae, which includes most European species) are immensely important for the functioning of some terrestrial ecosystems. Earthworm tunnels channel air, water and nutrients into deep layers of the soil, and facilitate root penetration. Their work improves soil structure and reduces runoff, thus decreasing the rates of erosion. By eating soil, plant litter and other materials (depending on the species), earthworms break down organic matter, helping decomposers like bacteria and fungi release its nutrients. Their food intake (2 to 20 tonnes of organic matter per hectare each year) ends up as castings (worm excrement), which are rich in nitrogen, phosphorus, potassium, magnesium and calcium, all minerals essential for plant growth. Thanks to their relentless burrowing, soil mixing and fertilizing, earthworms are important to soil formation, and consequently vital to plants and every organism that depends on them.

The common earthworm (Lumbricus terrestris) © Michael Linnenbach, Wikipedia Creative Commons

The value of earthworms was not lost on Charles Darwin. His 1881 book, The formation of vegetable mould, through the action of worms, published a few months before his death, was a revelation to the general public about the importance of these secretive and poorly known animals. The book was a huge success, selling 6,000 copies in the first year, more than On the Origin of Species when it was first published. 

Darwin and his worms in a caricature from Punch, 1882

Darwin calculated that in 10 years, castings from one acre of soil (0.4 ha) would form a 5 cm-thick layer of top soil (what he called ‘vegetable mould’). In his book’s closing paragraph, Darwin justified calling earthworms ‘nature’s ploughs’:

The plough is one of the most ancient and most valuable of mans (sic) inventions; but long before he existed the land was in fact regularly ploughed, and still continues to be thus ploughed by earth-worms. It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organised creatures.

Diagram of the formation of vegetable mould © Darwin, 1838. Proceedings of the Geological Society of London 2: 274-576

Considering earthworms’ impressive portfolio as nature’s engineers, we may think they are indispensable, or useful, everywhere. But they are not.

About 10,000 years ago, northern North America was overwhelmed by a vast ice sheet. If there were earthworms in the region, they were killed by the glaciation because there were none when the ice receded. So northern North America was earthworm-free until European settlers started to bring in plants and soil, which inevitably introduced worms such as the ‘night crawler’, the local name for the common earthworm Lumbricus terrestris.

American farmers and gardeners benefited from ‘nature’s ploughs’ as much as Europeans did, but it was a matter of time until earthworms made their way to native habitats such as hardwood forests. And in those environments, earthworms were not welcome at all.

The top layer of the forest floor – known as the litter layer – consists of leaves, bark and stems at different stages of decomposition. In North American native forests, the litter layer is broken down slowly, mainly by millipedes and mites. Organic material accumulates as blanket sheets, which are essential habitats for many insects, amphibians, birds, and flowers. 

Deep litter mound at the base of a pine tree © Hood, 2010. USDA Forest Service

When earthworms move in, decomposition accelerates dramatically. The litter layer is consumed in a few years, so that nutrients that have been slowly accumulating are released quickly; plants cannot absorb them all. With the loss of litter cover and nutrients, the understory fauna and flora become depleted. Dwindling understory plant biomass has secondary consequences; deer will have no option but to munch on young trees, and non-native plants may take advantage of the impoverished conditions to spread out. These problems worsened after the arrival of the Asian jumping worm (Amynthas agrestis), an earthworm native to Japan and Korea.

But the negative impact of earthworms is not restricted to the litter layer. In Canada, the abundance, biomass, and species richness of the insect fauna above ground were lower in forest plots with invasive earthworms than in earthworm-free areas. Insect abundance was reduced by 61% where earthworm biomass was highest.

Effects of earthworm-invasion status (low, mid, high; lighter to darker colour shades) on herbivore richness (morpho species), left; biomass (mg/m²), centre; and abundance (log₁₀ individuals/m²), right; in Alberta, Canada © Jochum et al., 2022. Biology Letters 18 (3)

The reasons for these effects are not known. Scarcity of some plants or altered soil conditions in earthworm areas may reduce the abundance and survival of herbivore and soil-dwelling invertebrates, which may affect the food chain. Invasive earthworms can decrease the concentrations of some plant metabolites used against leaf-chewing insects, so changes in plant chemistry may be involved. Direct links between invasive earthworms and pollinating insects have not been established, but it is safe to assume they exist. Pollinators are not likely to be immune to the profound changes in soil structure, flora composition, and arthropod diversity brought by earthworm activity.

Would this hoverfly be affected by the works of earthworms? Probably yes. © Forest Wander, Wikipedia Creative Commons

Even more worryingly, there is strong evidence that earthworm activity increases emissions of greenhouse gases. Dendrobaena octaedra, another earthworm native to Europe, seems to be spreading in Canadian boreal forests, which are important carbon reservoirs. Wherever this earthworm occurs, some of the carbon stock in the forest floor is lost in the form of carbon dioxide. So many soil ecologists have rightly voiced their concerns about a ‘global worming’.

The shenanigans of Darwin’s ‘nature’s ploughs’ in northern North America are cautionary tales about species taken to where they do not belong. Few could have predicted that earthworms, so beneficial to species and habitats in the Old Continent, are detrimental elsewhere. The buff-tailed bumble bee (Bombus terrestris) and the European honey bee (Apis mellifera) are protagonists of similar tales. 

The unpredictability of outcomes is a big worry. Only a fraction of invasive species are harmful, but those that are, can be disastrous. 

Kudzu (Pueraria spp.), ‘the vine that ate the South’, was purposely introduced into the United States for erosion control, but became an environmental nightmare. It is spreading at an estimated rate of 610 km²/year © Scott Ehardt, Wikipedia Creative Commons

Taynish NNR is Blooming Marvellous!

By Caroline Anderson

Over the next few months we look forward to regular updates from Caroline Anderson around Taynish National Nature Reserve. Caroline is a keen macro photographer, and her wonderful images and words will paint a vivid picture of one of our most popular reserves, which comes complete with a pollinator trail for you to enjoy.

Easter Monday, and an abundance of wildflowers greet you from the banking as you arrive at the Mill Car Park.   Amongst them Violet, Wood Sorrel, Wood Anemone, Primrose and Bluebell all willing the pollinators to pay them a visit.  

It was such a feeling of relief at the winter being over (technically) and spring having well and truly sprung.  Though not in great numbers, there were insects about.  I saw a few bees, hoverflies and other flying insects making the most of the sunshine.

A quick visit into the boardwalk with fingers crossed and a hopeful hop through the bog, but no damselflies just yet – maybe in the next week or two. 

Down at the picnic area where it is more sheltered, there was a bit more activity, a couple of Peacock butterflies around and the blossom on the cherry trees is just glorious and attracting some attention!   Despite one of the trees being damaged in a winter storm, it has blossomed beautifully. 

The daffs were also getting some insect attention – albeit from a very little insect on one, to a Peacock butterfly on another – but every little bit of pollinator action helps.

In the wood towards the shore the Stitchwort is starting to appear, it’s such a beautiful delicate wee plant.

Further into the woodland you will see Wood Sorrel – with its gorgeous purple and pink veining. 

Finally, a reminder, it’s not easy being green as this wee fly would tell you, so from a planter with some lavender to leaving a bit of the lawn to flourish with buttercups and daisies, you can do your bit to help these beautiful insects do their bit.  

Links : Visit Taynish National Nature Reserve

The butterfly, the plant, and the ant

By Athayde Tonhasca

For a long while we have had a gloomy selection of bad news to dip into: a virus epidemic, war crimes, the economy, the environment. Such a deluge overshadows the successes and feel good examples. And as inspiring tales go, it’s hard to beat the Large Blue Story. 

The large blue butterfly (Phengaris arion) has always been rare in Britain, but its numbers were found to be alarmingly low by 1972 and falling steadily thereafter. In 1979, it became extinct in the British Isles. At first collectors were blamed for the large blue’s demise, which was a reasonable explanation considering the rarity and the appeal of such a beautiful butterfly. But soon attention was directed to another possibility: the depletion of wild thyme (Thymus praecox), which is the main food for the butterfly’s early larval instars (developmental stages). It turned out that the food plant losses contributed to the large blue extinction, but the plot thickened considerably.

The large blue butterfly, Phengaris arion. The species’ taxonomy is a matter of dispute, so it is also known as Maculinea arion © PJC&Co, Wikipedia Creative Commons

Phengaris arion and about 75% of the 6,000 or so related species (family Lycaenidae) are myrmecophilous, that is, they are associated with ants. These butterfly-ant relationships vary in form and intensity, but in the case of the large blue, ants – specifically red ants – mean food: without them, the butterfly cannot survive.

A female large blue lays her eggs on the flower buds of wild thyme – wild marjoram (Origanum vulgare) would do, but it usually flowers too late in the season for the butterfly. The emerging caterpillars eat the wild thyme flower heads and seeds for the first few weeks of their lives, like any ordinary butterfly. Siblings are also fair game: if two eggs hatch on the same flower, one baby caterpillar will eat the other. Then the surviving larva goes full Dr Jekyll and Mr Hyde.

The caterpillar drops to the ground and starts releasing substances that attract worker ants, including pheromones that mimic the aroma of red ant larvae. When an ant bumps into it, the caterpillar stretches and twists to assume the shape of an ant larva. So instead of attacking the juicy, soft and nutritious caterpillar, the chemically mesmerised ants take their ‘wandering young’ back to their nest. There the caterpillar is cared for just like the ants’ own brood.

Once inside an ant nest, some lycaenid species adopt a cuckoo lifestyle; they induce the ants to nurse and feed them through regurgitation. Not the large blue: it feeds on ant larvae, all the while secreting sugary substances to keep the ant workers happy. Related species show the same behaviour.

A greater large blue (Phengaris arionides) caterpillar feeding on Myrmica kotokui larvae © T. Komatsu, from Ueda et al., 2016. Scientific Reports 6: 36364

The caterpillar carries on eating ant grubs until it pupates the following spring. The emerging adult crawls to the surface and seeks refuge in the nearby vegetation, where it expands its wings and flies away in search of a mate. 

A gravid female butterfly (1) is attracted to wild marjoram (2), and lays her eggs on suitable flower buds (3). A fourth-instar caterpillar drops to the ground and is ‘adopted’ by ants (4). The caterpillar spends 11 months inside the ants’ nest, feeding on their brood (5). Artwork by Elisa Plazio at Casacci et al., 2019. Frontiers in Ecology and Evolution 7: 454

The above was a summary of the complex biology and ecology of the large blue: go to UK butterflies for the full story.

The large blue’s reliance on wild thyme and red ants has been known for a long time, but none of the conservation efforts managed to prevent its extinction in 1979. Things started to change when a PhD student – today professor Jeremy Thomas, OBE, President of the Royal Entomological Society – made a crucial discovery. Not just any red ant would do for the large blue. It needs one specific species: Myrmica sabuleti (M. scabrinodis is an alternative host, but butterfly survival is poor with this ant).

Myrmica sabuleti, the crucial host for the large blue © B. Schoenmakers, Wikipedia Creative Commons

Thomas’ finding opened up a whole new perspective for large blue conservation. If Myrmica sabuleti populations are not doing well, the butterfly cannot do well either, regardless of the host plant’s quantity and condition.

The survival and abundance of this particular red ant depend largely on one factor: sunshine, which keeps their nests sufficiently warm. If the grasses that grow together with wild thyme are too tall, the temperature of ant nests will drop; the colonies will fail or be too small to sustain populations of large blue. One caterpillar may require 200 ant larvae to reach adulthood, and about 350 ant workers may be needed to rear a single caterpillar. So fencing, which was thought to help the butterfly by keeping thyme-munchers at bay, turned out to be bad for the ants. Without grazers, the ground became too cold and wet.

Wild thyme habitat in full sunshine maintains healthy M. sabuleti colonies © GT1976, Wikipedia Creative Commons

Armed with this information, Nature Conservancy (now Natural England) and the Centre for Ecology and Hydrology launched a reintroduction programme, and its linchpin was the creation and management of adequate conditions for both the butterfly and the ant. Conservation organisations, land managers and volunteers set out to monitor large blue and M. sabuleti populations, manage grazing to keep the grass short, clear scrub and plant wild thyme. When a pilot site was considered in favourable condition in 1983, large blue specimens from Sweden were brought in. More releases followed at several suitable sites during subsequent years. Today, large blue colonies are more abundant and larger than they were in the 1950s.

The rescue of the large blue butterfly is a textbook case of species conservation, known and celebrated around the world. It inspires and shows us that science, hard work and goodwill go a long way to restore and protect our natural world.

Ch-ch-changes

It’s a classic of its era. David Bowie in 1971 with ‘Changes’. The theme of the song captured the mood of the early seventies. The phrase ‘Changes’ could also apply to today’s environment inspired shift in the way public grasslands are managed.  In Local Authorities up and down the land the very way public greenspace is viewed is under serious examination.  Ch-ch-changes indeed.

Greenspaces which are managed for nature and people are very much the way forward. The health and wellbeing agenda demands it, the biodiversity crisis demands it, and the climate change crisis likewise.  Glasgow, Edinburgh, Moray, Aberdeen, South Lanarkshire … the list of Local Authorities who are transforming grasslands positively for wildlife and community benefit continues to grow.

There is no magic wand to solving the environmental challenges we face but the series of trials in Perth and Kinross to test the impact revised grounds maintenance systems will tackle head on the twin threats of biodiversity loss and climate change.  It’s a welcome local move which includes a host of positive actions.

The range of new approaches comprises a suite of helpful changes. Perth and Kinross council will be leavingsome areas with longer grass, and are set on reducing the use of weedkiller and strimming, particularly around trees.  That trio of actions will certainly be warmly received.  The result will be new and improved habitats for wildlife, with a welcome foraging boost for insects, including our vital pollinators. A reduced use of fuel will offer both financial and a carbon savings.

There is a greater than ever appreciation of the value of verges and wildflower strips, and increasing concern about the frequency with which patches such as these often suffer from mowing which stifles plant diversity and, in an instant, removes vital feeding sources for pollinators.

However, the plans don’t stop with changing what are counter-productive ‘tidy’ management practices. The ambitious new approach will see more trees planted, and these will be native species, either grown from seed or locally sourced. Indeed that approach will be supplemented with a continuation of the policy of using cuttings from the area’s existing sites to grow-on their own shrubs, thus helping to reduce the carbon footprint and reduce the risk of pests and diseases.  

There is space too for leaving areas to rewild naturally.

So where are these trials taking place?  The Perth & Kinross Council website carries details, including maps, of the trial sites. 

Of the 29 sites listed seven are in the city of Perth itself, including significant patches in the popuar South Inch and along the busy Dunkeld Road.  Smaller communities such as Wolfhill, Luncarty and Pitcairngreen are included in the plans.

Change can be tricky – and persuasive communications vital if projects are to succeed. But the council are on firm ground, they are changing practices to address multiple challenges and can emphasise the benefits for biodiversity, aesthetic appeal and climate change mitigation. 

The council will seek to balance the needs of local residents with the needs of wildlife, but it shouldn’t be difficult to ensure that the changes are complementary, understood and appreciated. Good greenspaces for nature and people are not mutually exclusive.

‘Changes’ didn’t propel David Bowie to number one, that came later with songs such as ‘Under Pressure’. And perhaps for our purposes that song title also fits our story well. Pollinators are indeed under pressure, and actions such as those proposed by Perth and Kinross can make a huge difference. Here’s to changes.

Find out more

About the Perth & Kinross public consultation which is here = Perth & Kinross Council Citizen Space – Citizen Space (pkc.gov.uk)

Discover the 42 sites being developed as ‘naturalised grass’ with no management, and the 8 wildflower meadow trials that will be cut and lifted @ Encouraging wildlife and biodiversity in parks and open spaces – Perth & Kinross Council (pkc.gov.uk)

View the Perth & Kinross Storymap

Changes in the menu

By Athayde Tonhasca

If in a perambulation outdoors you spot a bee slipping into a hole in the ground, chances are it’s an Andrena species. Many bees are fossorial (from the Latin fossor for ‘digger’, it refers to species that excavate the soil and spend most of their life underground), but Andrena is the most common group by far. With 68 species recorded in Britain and around 1,400 described species worldwide, this is one the largest animal genera. 

Like all mining bees, Andrena species are solitary: a female builds her own nest chambers in which she stocks pollen and lays her eggs. Although each bee minds her own business, many species are communal nesters, sometimes forming aggregations thousand strong. Some species like the chocolate mining bee (Andrena scotica) use a common nest entrance, giving the impression of social behaviour. But once beyond the front door, each bee digs her own side tunnel and provisions her own chambers.

A group of chocolate mining bees hanging around a communal nest entrance in a wall in Perth 

These bee concentrations frighten some people. Beekeepers and council officers have been summoned to deal with ‘swarms,’ only to find the comings and goings of mining bees. Worse, people afraid of being stung or concerned about damage to buildings or lawns have wiped out whole colonies with insecticides. But these citizens are mistaken on both counts. Solitary bees are docile and never go out of their way to attack people or animals; besides, their sting is too weak to penetrate human skin. And their nesting galleries are temporary and too small to cause any damage.

Many bee species collect pollen on their corbiculae (pollen baskets) or scopa, which is an area of dense, stiff hairs on their hind legs or on the underside of their abdomen. Female Andrena bees have an additional collecting apparatus: a large brush of curled hairs on the hind legs called floccus. So these bees manage to carry large loads of pollen, which increases the chances of pollination. Because of their diversity, abundance and efficiency, Andrena bees must contribute to the pollination of crops, trees and wild flowers, although we don’t have detailed information about these services.

A grey-backed mining bee (Andrena vaga) loaded with pollen © Agroscience RLP, Wikipedia Creative Commons

As Andrena bees and other pollinators depend on flowers, they are particularly vulnerable to losses or impoverishment of plant biodiversity. So they were caught in the environmental maelstrom unleashed by the Second World War.

Under the trauma of shortages and threat of famine, the UK government was determined to make the country self-sufficient in food production. In came the 1947 Agriculture Act, which changed Britain forever. The subsequent rapid agricultural intensification led to increased efficiency and production, but there was a price to pay: modern farming practices severely reduced the areas of natural and semi-natural habitats, and depleted biodiversity.

A modern farm offers few opportunities to pollinators © European Environment Agency

Fortuitous museum collections offered an exceptional opportunity to gauge the effects of these historical habitat changes on the British Andrena fauna. By comparing pollen grains attached to Andrena bees collected between 1941 and 1949 with bees collected between 1985 and 2016, Wood & Roberts (Biological Conservation 215: 72–80) obtained a glimpse of bee diets before and after the onset of agricultural intensification.

Pollen loads from both periods revealed one particularly significant shift: a move from Rosaceae family (hawthorns, cherries, crab apple) to oilseed rape (Brassica napus). These results were not surprising: hedgerows have been cut down for the sake of improving farming operations, so many woody Rosaceae plants have disappeared from the landscape. At the same time, oilseed rape boomed: British production has risen from a few thousand tonnes in the 1970s to a couple of million today. Worldwide production has increased six-fold between 1975 and 2007, and this crop has become the third largest source of vegetable oil in the world.

Change in the offerings: from a hawthorn hedge to an oilseed rape field © David Hawgood (L) and Nas2, Wikipedia Creative Commons

The change from small fields criss-crossed by hedgerows and uncultivated plants to monotonous oilseed rape crops is likely to affect Andrena bees in different degrees. Most species are polylectic, that is, they collect pollen from various types of flowers. But some species are oligolectic: they collect pollen from a few related plant species. Pollen specialisation is an obvious problem when the landscape is awash with the wrong type of flowers, but hard data are scant. Landscape simplification may have contributed to the decline of the blackthorn mining bee (Andrena varians), which collects pollen mostly from early-flowering blackthorn and hawthorn. Other species may have been hit as well with the loss of swathes of uncultivated plants. So for example the decline of the grey-banded mining bee (Andrena denticulata) may be linked to lower availability of weedy species from the Asteraceae family such as daisies and aster, which are the bee’s main pollen sources. 

Habitat loss has significantly affected wild bees in North America and Western Europe – and probably elsewhere too. Reversing the trend by diversifying agricultural landscapes and preserving the remaining natural habitats are the best means to mitigate the effects of the post-war ‘green revolution’ and safeguard the pollination services provided by Andrena and other bees.

Two bees punished by agricultural changes: the blackthorn (L) and grey-banded mining bees © Aiwok (L), and Sandy Rae, Wikipedia Creative Commons

Nectar network

Good things are certainly happening in Ayrshire for pollinators. An impressive range of partners, with an equally impressive range of sites, are dramatically improving pollinator habitat, whilst introducing new audiences to the fascinating role of these vital insects.

Irvine beach Park Pond Meadow – (c) Lynne Bates

A vibrant combination of willing volunteers, enthusiastic partners and respected specialists bodes well for a winning combination, and this is certainly borne out by the Scottish Wildlife Trust-led Irvine to Girvan ‘Nectar Network’ along the Ayrshire coast.

Calling upon the expertise of environmental agencies, working closely with local councils, and harnessing the support of students and staff at Scotland’s Rural College (SRUC), the Nectar Network is a catalyst in expanding knowledge and skills to create and manage pollinator habitats

Last year volunteer surveyors were trained, kitted out and allocated sites along the coast to systematically monitor the biodiversity of the area. Methods employed included the increasingly popular Flower-Insect Timed (FIT) counts, allied to conventional transect walks, which allow for a better monitoring of the health of pollinators across the landscape. 

It is often said that habitat improvements and creation are the single most effective thing we can do to help pollinators. And there are so many examples in Ayrshire that it takes the breath away. Here’s a flavour of what’s been going on …

• The children at Symington Primary School sowed their own mini meadow with wildflowers and yellow rattle, helped by the enthusiastic South Ayrshire Rangers. 
• The Rotary Club of Prestwick enhanced an unused site next to Prestwick Railway Station, sowing wildflowers to provide food for pollinators and interest for commuters.
• Greenkeepers at The National Centre for Bowling, Ayr removed turf and sowed native wildflower seeds in two large areas within the grounds to encourage pollinators in the area.
• A new wildflower meadow at Little Acorns Forest School, Auchincruive created last year with the help of the children, volunteers and parents has been a colourful success. Providing opportunities for surveying and identification plus outdoor learning and creating a real buzz for pollinators and people.
• Two large new wildflower meadows created on public greenspaces in Irvine, adjacent to Scottish Wildlife Trust Wildlife Reserves, not only improves connectivity for species moving across the landscape but provides visual interest for locals visiting the sites. 
• Eglinton Community Gardens in North Ayrshire called upon the help of 36 employees from a local company to prepare and sow a large new meadow, increasing the abundance of forage and nesting opportunities.
• The new Pond Meadow sown in autumn 2020 at Irvine Beach Park was cut, collected and the green hay used to extend the Dragon Meadow. A total of two hectares of the park is now wildflower meadow habitat which will support a range of wildlife, food for pollinators and provide colour and visual interest for visitors to the park. 
• Over 400 trees were planted at Low Pinmore Farm to create a new flowering hedge to connect existing pollinator areas and provide vital food and nesting areas

By any measure that’s an impressive catalogue of activities. With so many partners and such a wide range of sites, Ayrshire certainly looks set to be an area where pollinators can thrive. However, that’s not all that’s been happening.

One growing area of interest focuses on the potential of roadside verges to help pollinators. 

Local volunteer surveyors were trained for a new partnership with Symington Community Council’s Wildflower Project. A great example of partnership working the project draws together Transport Scotland, Amey (who operate and maintain motorway and trunk road technology infrastructure across Scotland) and South Ayrshire Council in exploring ways to improve verge management for pollinators. 

The method is strikingly simple, yet effective. The grass verge on the outskirts of the village has been left to grow and will only be cut in late summer, in the meantime spring and summer will see weekly pollinator and plant survey undertaken by the volunteers to help to inform the next stage of the project. 

Coming on the back of Plantlife’s national drive to raise awareness of the potential of roadside verges for pollinators this is a fantastic development to see in Scotland.

Another key focus is the connection between Kidney Vetch and the Small Blue, Britain’s smallest butterfly. The Ayrshire Small Blue was given a boost last year, through support from the local Garnock Connections project. Kidney Vetch is the sole larval foodplant of the Small Blue so determining its current status along the Ayrshire coast is crucial. Working alongside Lynne Bates who is the Nectar Network Co-ordinator at Scottish Wildlife Trust was Butterfly Conservation’s Tom Prescott.

In a region famous for its golf courses, the work to protect and extend the range of sites supporting Kidney Vetch cleverly harnessed the knowledge of local greenkeepers and golf course managers. Detailed surveys determined the current status of Kidney Vetch, which also helps identify sites where more beneficial planting can take place.

The results were impressive, with over 40 people taking part in online training workshops, 33 volunteers surveying over a dozen sites, and no fewer than eight golf courses from Irvine to Troon getting involved.

As a result, kidney vetch was recorded at 116 locations, with over 3,500 plants being recorded. All in all, a staggering 55,000 flower or seed heads were counted. A student from SRUC is now analysing the survey forms to map the distribution (and gaps) to help steer future actions.

The Ayrshire coast is proving a hot spot for pollinator friendly activity and through sharing learning and knowledge with key organisations, partners, businesses and individuals, everyone is playing an important role in creating a network for pollinators.

Find out more @ Irvine to Girvan Nectar Network

Many thanks to Lynne Bates, who is the Nectar Network Co-ordinator at Scottish Wildlife Trust, for all her help with this article.

Little Acorns meadow July 2021 – (c) Emily Hamalainen

            Low Pinmore Farm hedge planting – (c) Lynne Bates

Kidney Vetch survey training Gailes Marsh Wildlife Reserve

On the trail of pollinators

We have reached that time of year when across Scotland our pollinator trail panels go back out.  Several of our National Nature Reserves now offer a fascinating insight into the world of pollinators, and over the coming weeks we will take a look at the pollinator trails you can visit.

Creag Meagaidh is understandably celebrated by many as a magnificent ‘Munro’. At a whopping 1128m it is a magnet for hill walkers and the path to Lochan a Choire is one of the great introductions to a mountain day out. From here you look up to ‘The Window’,  a distinctive view in the Scottish hillwalking scene, and a striking visual reference point from many other summits.

The National Nature Reserve, purchased for the nation in 1985, carries the same name as the mountain (the name actually covers both the mountain summit itself and the ‘range’ here).  It’s a haven for a stunning variety of wildlife, as many of you will know – golden eagle, mountain hare, black grouse, dotterel, snow bunting, peregrine falcon … this list goes on. 

Down from the peaks you will find lovely mixed woodland boasting alder, oak and rowan, which vies for your attention with bird cherry, holly and willow (willows (Salix spp) are such an important early season forage resource for bumblebees queens).  For bird watchers, given the variety of habitats, the reserve is a huge draw.

There are also flowering hedgerows and areas of meadow. The flowers you can find on this reserve can set the pulse racing. To list them all would take an age, but consider some of the highlights from a pollinator perspective – devil’s bit scabious, tormentil, bluebell, creeping buttercup, primrose, wood anemone, speedwell, meadowsweet. Even on some higher stretches heather and bilberry offer sustenance for pollinators.

There are two low-level routes – the Alder and An Sidhean trails – for the non-mountaineer to enjoy which carry the popular pollinator signs. 

Rory Richardson is the welcoming reserve manager at Creag Meagaidh and is an advocate for making days out at the reserve as enjoyable and educational as possible.  His commitment to making a home for pollinators here stretches back some time now. “We’ve been adding flowering hedgerows on a regular basis at Creag Meagaidh, we have two hawthorn hedges and a further 400 metres of mixed tree hedging,” he explains, and “we also plant around a quarter of an acre of wildflower mix each year.” 

Many people will continue to cherish this as a reserve in which mountain terrain features heavily.  Others will associate it with a policy of impressive restoration through tackling degradation of the area due to over grazing. Yet increasingly it is the sheer variety of experience on offer that appeals to visitors. In Gaelic ‘Creag Meagaidh’ is said to mean the ‘crag at the bog’, but with so many different habitats jammed into this popular corner it can’t have been easy to settle on but a single name.

The pollinator trails offer a relaxing introduction to this fabulous reserve. Within easy striking distance of the car park, they lure both passing visitors and those intent on lingering. The trail panels reveal a wealth of information on species and habitats around the site, and crucially there are plenty of take-home messages to inspire visitors to carry out pollinator-friendly practices back on their home patch.

Lofty aspirations indeed.

Find out more about Creag Meagaidh National Nature Reserve.

Pictures 1 and 2 (c) Rory Richardson

The Disproportionate Value of ‘Weeds’ to Pollinators and Biodiversity

By Nicholas Balfour

We have a guest blog today from Nicholas Balfour, Postdoctoral Researcher at the University of Sussex, which takes a look at the occasionally controversial and complex subject of weeds.

“Weeds are contentious. Agricultural weeds can cause yield losses in arable and pastureland. However, they can also be of great importance to both flower-visiting and herbivorous insects. In our latest study we used multiple datasets to compare the biodiversity value of the plant species classified as ‘injurious weeds’ by the 1959 Weeds Act, with those species stipulated by DEFRA for pollinator targeted agri-environmental options.

Bumbles bees (Bombus spp.) on spear thistle (Cirsium vulgare) Photo – Paul Leyland

“In the European Union and the UK, financial support has been provided for farmers to encourage wildlife. For pollinating insects, funding has been available to sow wildflower mixes (e.g. “Flower-rich margins and plots”, “Autumn sown bumblebird mix”) with species such as red clover (Trifolium pratense) and wild marjoram (Origanum vulgare).

“In the UK five species of native wildflowers are classified as “injurious” in the 1959 Weeds Act. Three of them are frequently visited by many species of bees and other insects – ragwort (Jacobaea vulgaris) and two thistles (Cirsium arvense, C. vulgare). The other two are docks (Rumex crispus and R. obtusifolius), which are mainly wind-pollinated. All five are important larval foodplants for many insects, including several nationally rare or scarce species and the UK Biodiversity Action Plan species, the cinnabar moth (Tyria jacobaeae).

“In this study, we quantify and identify the insects foraging on ragwort, the two thistles and other wildflowers growing in six pasture or ex-pasture sites in East Sussex. We found that both the abundance and diversity of pollinators visiting the weed species averaged twice that of the DEFRA recommended plants.

Ivy bees (Colletes hederae) visiting creeping thistle (Cirsium arvense). Photo – Allan Burrows

“A subsequent analysis of scientific literature mirrored this result. The Database of Pollinator Interactions dataset showed that four times as many pollinator species and five times more conservation-listed species have been recorded visiting the three insect-pollinated weeds. Of the 387 plant species analysed, in terms of pollinator species recorded, the weeds were ranked 4th (C. arvense), 6th (J. vulgaris), and 13th (C. vulgare). Similarly, the Database of Insects and their Food Plants showed that twice as many herbivorous insect species are associated with the five weed species.

“Several factors are probably responsible for this pattern. All five injurious weeds are widely distributed. The three insect-pollinated species have open flowers that allow access to a wide variety of species, and they produce, on average, four times more nectar sugar than the DEFRA recommended plant species.

“Freedom of information requests to public bodies such as councils, Natural England and Highways England indicate that c. £10 million per year is spent controlling injurious weeds. Meanwhile, the cost of the four pollinator-targeted agri-environmental options in the UK exceeds £40m annually.

“Alarmingly, most local councils indicated that they actively control ragwort, thus classing it in the same bracket as invasive, non-native species such as Japanese knotweed (Reynoutria japonica). This is very likely due to the Ragwort Control Bill 2003. As such, the implementation of this legislation probably deserves greater scrutiny, especially given that the evidence underpinning it is questionable.

Ragwort pulling. Photo – Catherine Whyte

“Our results clearly show that weeds have an underappreciated value in supporting our natural biodiversity. Unfortunately, current UK agricultural policy encourages neither landsparing for, nor landsharing with, weeds. For example, DEFRA provided guidance on controlling weeds in agri-environmental areas managed for biodiversity.

“ScotGov recently stated their intention of transforming Scotland into a ‘global leader’ in sustainable and regenerative agriculture. It also committed to ‘the restoration of nature through biodiversity’ on farmland.

“Given their value to biodiversity, we hope forthcoming policy changes will provide sufficient directives and financial incentives to persuade land managers to tolerate injurious weeds. Any changes would, of course, need to consider the balance of practicality, cost (impacts on crop yields and plants of conservation concern), and benefits (effects on biodiversity, ecosystem services and direct cost savings) of weed toleration. Thus, the challenge of reconciling the conflicts between agricultural production and these native and biodiverse species should be a renewed priority to land managers, researchers and policymakers.

“Despite their ecological value, many common UK wildflowers that are valuable to flower-visiting and herbivorous insects are often overlooked or even disliked, as exemplified by species such as ivy and bramble. 

“Encouragingly, however, last summer the ‘Weed Thriller’ garden at the Royal Horticultural Society’s Tatton Park flower show, full of ragwort and other weed species, was awarded a gold medal. Isabella Tree’s recent book ‘Wilding’ devoted an entire chapter to ragwort. A petition calling for the UK government to repeal the Weeds Act was halted only for the 2019 General Election. Hence, it appears there is a growing awareness amongst the British public of the conservation utility of this group of often maligned and underappreciated native wildflowers.”

Further reading:

Read the research in full at : Balfour, N.J. & Ratnieks, F.L.W. (2022) The disproportionate value of ‘weeds’ to pollinators and biodiversity. Journal of Applied Ecology.

Boys’ night out

By Athayde Tonhasca

We humans spend between 25 to 35% of our lifespan sleeping. It’s a significant chunk of time in the land of Nod, so sleep must be vital. But surprisingly, doctors and scientists are not sure why we sleep so much – or at all, for that matter. A period of unconsciousness may be required so that our body can repair itself and restore some physiological or chemical functions; it could help us conserve energy, especially at night, when the search for food is less efficient. 

Two girls on the stove bench, Albert Anker, 1895

Whatever the reason, we need our resting period. And so do other animals, including insects. In the case of bees and wasps, females have the obvious option of a cosy hive or a nest to tuck into for the night. But males do not: they are not welcomed back once they mature and leave the nest, so they are destined for a vagabond life. When the night comes and the temperature drops, bees enter a state of torpor. Until the morning sun heats them up again, they have to rough it.

Flowers are the bedding choice for males of many species such as the large scissor-bee (Chelostoma florisomne). Linnaeus originally named it Apis florisomnis, a Latin combination of floris (flowers) and somnus (sleep), which explains its other common name: the sleepy carpenter bee. On early mornings or overcast days, sluggish males are found clinging to the stamens of buttercup flowers, which are the single source of pollen for this bee. These flowery sleeping arrangements are helpful for meeting females during daytime. They also turn males of some species into good pollinators, as it is the case of squash bees.

A sleepy carpenter bee investigating the males’ sleeping quarters © European Environment Agency

Flowers may offer some protection for bees that snuggle and curl up among the petals, but sheltering doesn’t seem to be a priority since many bees just sleep in the open. If you visit a garden during early morning or early evening, you may spot bumble bees slumbering on top of a flower, or even hanging upside-down from a blossom or under a leaf. Most of them are males, but the odd female may join them if she’s caught outside when temperature drops quickly at sunset.

Sleeping bumble bees clinging to a Welsh onion (Allium fistulosum) inflorescence

Some bees and wasps don’t bother to make themselves comfortable for the night. They hang from the end of a twig, a dried flower head or a long thin stem, clamped on with their mandibles. We don’t know why they sleep like this; perhaps it makes them less visible to predators, who may mistake them for plant extensions (you can watch a bee clinging to a plant and refusing to be woken up). 

A Nomada sp. cuckoo bee sleeping anchored by its mandibles © Giles Gonthier, Wikipedia Creative Commons

Male solitary bees are not much into socialising: they avoid each other, when are not being downright aggressive. But when night falls, males of some species spend the night close together, forming clusters of bees that cling from branches or flowers. Not only that, these males tend to return again and again to the same spot each evening for their sleep. Gregarious sleeping seems like a dangerous life choice: such concentrations of lethargic bees must tempt many a predator. One possible explanation for this behaviour is the dilution effect: the larger the group of prey, the smaller the chance of any individual being the victim of a predator. Some fish, penguins and mammals that live in the open resort to this type of defence mechanism.

A long-horned bee (Melissodes sp.) slumber party © Todd Sonfileth, Oregon Public Broadcasting

We don’t have no much information about the consequences of sleeping in the open for male bees. But when you tuck in tonight, remember that a peaceful, uneventful sleep is not a given for everybody.    

A bee sleeping in a flower © Todd Esque, U.S. Geological Survey